Writing with Inform The complete documentation for Inform 7 presented in a single plain text file. The twenty-one chapters are each divided into sections. The sections refer to Examples, numbered upwards from 1 throughout the book: these Examples are presented in numerical order at the end of the main text. Chapter 1: Welcome to Inform 1.1. Preface 1.2. Acknowledgements 1.3. The facing pages 1.4. The Go! button 1.5. The Replay button 1.6. The Index and Errors panels 1.7. The Skein 1.8. A short Skein tutorial 1.9. Summary of the Skein and Transcript 1.10. The Inspector Chapter 2: The Source Text 2.1. Creating the world 2.2. Making rules 2.3. Punctuation 2.4. Problems 2.5. Headings 2.6. Why using headings is a good idea 2.7. The SHOWME command 2.8. The TEST command 2.9. Material not for release 2.10. Installing extensions 2.11. Including extensions 2.12. Use options 2.13. Administering classroom use 2.14. Limits and the Settings panel 2.15. What to do about a bug 2.16. Does Inform really understand English? 2.17. Review of Chapter 2: The Source Text Chapter 3: Things 3.1. Descriptions 3.2. Rooms and the map 3.3. One-way connections 3.4. Regions and the index map 3.5. Kinds 3.6. Either/or properties 3.7. Properties depend on kind 3.8. Scenery 3.9. Backdrops 3.10. Properties holding text 3.11. Two descriptions of things 3.12. Doors 3.13. Locks and keys 3.14. Devices and descriptions 3.15. Light and darkness 3.16. Vehicles and pushable things 3.17. Men, women and animals 3.18. Articles and proper names 3.19. Carrying capacity 3.20. Possessions and clothing 3.21. The player's holdall 3.22. Food 3.23. Parts of things 3.24. Concealment 3.25. The location of something 3.26. Directions 3.27. Review of Chapter 3: Things Chapter 4: Kinds 4.1. New kinds 4.2. Using new kinds 4.3. Degrees of certainty 4.4. Plural assertions 4.5. Kinds of value 4.6. Properties again 4.7. New either/or properties 4.8. New value properties 4.9. Using new kinds of value in properties 4.10. Conditions of things 4.11. Default values of kinds 4.12. Values that vary 4.13. Duplicates 4.14. Assemblies and body parts 4.15. Names made in assembly 4.16. Postscript on simulation 4.17. Review of Chapter 4: Kinds Chapter 5: Text 5.1. Text with substitutions 5.2. How Inform reads quoted text 5.3. Text which names things 5.4. Text with numbers 5.5. Text with lists 5.6. Text with variations 5.7. Text with random alternatives 5.8. Line breaks and paragraph breaks 5.9. Text with type styles 5.10. Accented letters 5.11. Unicode characters 5.12. Displaying quotations 5.13. Making new substitutions 5.14. Review of Chapter 5: Text Chapter 6: Descriptions 6.1. What are descriptions? 6.2. Adjectives and nouns 6.3. Sources of adjectives 6.4. Defining new adjectives 6.5. Defining adjectives for values 6.6. Whereabouts on a scale? 6.7. Comparatives 6.8. Superlatives 6.9. Which and who 6.10. Existence and there 6.11. A word about in 6.12. A word about nothing 6.13. To be able to see and touch 6.14. Adjacent rooms and routes through the map 6.15. All, each and every 6.16. Counting while comparing 6.17. Review of Chapter 6: Descriptions Chapter 7: Basic Actions 7.1. Actions 7.2. Instead rules 7.3. Before rules 7.4. Try and try silently 7.5. After rules 7.6. Reading and talking 7.7. The other four senses 7.8. Rules applying to more than one action 7.9. All actions and exceptional actions 7.10. The noun and the second noun 7.11. In rooms and regions 7.12. In the presence of, and when 7.13. Going from, going to 7.14. Going by, going through, going with 7.15. Kinds of action 7.16. Repeated actions 7.17. Actions on consecutive turns 7.18. Postscript on actions 7.19. Review of Chapter 7: Basic Actions Chapter 8: Change 8.1. Change of values that vary 8.2. Changing the command prompt 8.3. Changing the status line 8.4. Change of either/or properties 8.5. Change of properties with values 8.6. Whose property? 8.7. Moving things 8.8. Moving backdrops 8.9. Moving the player 8.10. Removing things from play 8.11. Now... 8.12. Increasing and decreasing 8.13. Checking on whereabouts 8.14. More flexible descriptions of whereabouts 8.15. Calling names 8.16. Counting the number of things 8.17. Looking at containment by hand 8.18. Randomness 8.19. Random choices of things 8.20. Review of Chapter 8: Change Chapter 9: Time 9.1. When play begins 9.2. Awarding points 9.3. Introducing tables: rankings 9.4. When play ends 9.5. Every turn 9.6. The time of day 9.7. Telling the time 9.8. Approximate times, lengths of time 9.9. Comparing and shifting times 9.10. Calculating times 9.11. Future events 9.12. Actions as conditions 9.13. The past and perfect tenses 9.14. How many times? 9.15. How many turns? 9.16. Review of Chapter 9: Time Chapter 10: Scenes 10.1. Introduction to scenes 10.2. Creating a scene 10.3. Using the Scene index 10.4. During scenes 10.5. Linking scenes together 10.6. More general linkages 10.7. Multiple beginnings and repeats 10.8. Multiple endings 10.9. Why are scenes designed this way? 10.10. Review of Chapter 10: Scenes Chapter 11: Phrases 11.1. What are phrases? 11.2. The phrasebook 11.3. Pattern matching 11.4. The showme phrase 11.5. Conditions and questions 11.6. If 11.7. Begin and end 11.8. Otherwise 11.9. While 11.10. Repeat 11.11. Repeat running through 11.12. Next and break 11.13. Stop 11.14. Phrase options 11.15. Let and temporary variables 11.16. New conditions, new adjectives 11.17. Phrases to decide other things 11.18. The value after and the value before 11.19. Review of Chapter 11: Phrases Chapter 12: Advanced Actions 12.1. A recap of actions 12.2. How actions are processed 12.3. Giving instructions to other people 12.4. Persuasion 12.5. Unsuccessful attempts 12.6. Spontaneous actions by other people 12.7. New actions 12.8. Irregular English verbs 12.9. Check, carry out, report 12.10. Action variables 12.11. Making actions work for other people 12.12. Check rules for actions by other people 12.13. Report rules for actions by other people 12.14. Actions for any actor 12.15. Out of world actions 12.16. Reaching inside and reaching outside rules 12.17. Visible vs touchable vs carried 12.18. Changing reachability 12.19. Changing visibility 12.20. Stored actions 12.21. Guidelines on how to write rules about actions Chapter 13: Relations 13.1. Sentence verbs 13.2. What sentences are made up from 13.3. What are relations? 13.4. To carry, to wear, to have 13.5. Making new relations 13.6. Making reciprocal relations 13.7. Relations in groups 13.8. The built-in verbs and their meanings 13.9. Defining new assertion verbs 13.10. Defining new prepositions 13.11. Indirect relations 13.12. Relations which express conditions 13.13. Relations involving values 13.14. Relations as values in their own right 13.15. Temporary relations 13.16. What are relations for? 13.17. Review of Chapter 13: Relations Chapter 14: Numbers and Equations 14.1. How do we measure things? 14.2. Numbers 14.3. Units 14.4. Multiple notations 14.5. Scaling and equivalents 14.6. Named notations 14.7. Making the verb "to weigh" 14.8. The Metric Units extension 14.9. Notations including more than one number 14.10. The parts of a number specification 14.11. Understanding specified numbers 14.12. Totals 14.13. Equations 14.14. Arithmetic with units 14.15. Multiplication of units 14.16. Review of Chapter 14: Numbers and Equations Chapter 15: Tables 15.1. Laying out tables 15.2. Looking up entries 15.3. Corresponding entries 15.4. Changing entries 15.5. Choosing rows 15.6. Repeating through tables 15.7. Blank entries 15.8. Blank columns 15.9. Blank rows 15.10. Adding and removing rows 15.11. Sorting 15.12. Listed in... 15.13. Topic columns 15.14. Another scoring example 15.15. Varying which table to look at 15.16. Defining things with tables 15.17. Defining values with tables 15.18. Table continuations 15.19. Table amendments Chapter 16: Understanding 16.1. Understand 16.2. New commands for old grammar 16.3. Overriding existing commands 16.4. Standard tokens of grammar 16.5. The text token 16.6. Actions applying to kinds of value 16.7. Understanding any, understanding rooms 16.8. Understanding names 16.9. Understanding kinds of value 16.10. Commands consisting only of nouns 16.11. Understanding values 16.12. This/that 16.13. New tokens 16.14. Tokens can produce values 16.15. Understanding things by their properties 16.16. Understanding things by their relations 16.17. Context: understanding when 16.18. Changing the meaning of pronouns 16.19. Does the player mean... 16.20. Understanding mistakes 16.21. Precedence 16.22. Review of Chapter 16: Understanding Chapter 17: Activities 17.1. What are activities? 17.2. How activities work 17.3. Rules applied to activities 17.4. While clauses 17.5. New activities 17.6. Activity variables 17.7. Beginning and ending activities manually 17.8. Introduction to the list of built-in activities 17.9. Deciding the concealed possessions of something 17.10. Printing the name of something 17.11. Printing the plural name of something 17.12. Printing a number of something 17.13. Listing contents of something 17.14. Grouping together something 17.15. Printing room description details of something 17.16. Printing a refusal to act in the dark 17.17. Printing the announcement of darkness 17.18. Printing the announcement of light 17.19. Printing the name of a dark room 17.20. Printing the description of a dark room 17.21. Constructing the status line 17.22. Writing a paragraph about 17.23. Listing nondescript items of something 17.24. Printing the locale description of something 17.25. Choosing notable locale objects for something 17.26. Printing a locale paragraph about 17.27. Deciding the scope of something 17.28. Clarifying the parser's choice of something 17.29. Asking which do you mean 17.30. Supplying a missing noun/second noun 17.31. Reading a command 17.32. Implicitly taking something 17.33. Printing a parser error 17.34. Deciding whether all includes 17.35. Printing the banner text 17.36. Printing the player's obituary 17.37. Amusing a victorious player 17.38. Starting the virtual machine 17.39. Review of Chapter 17: Activities Chapter 18: Rulebooks 18.1. On rules 18.2. Named rules and rulebooks 18.3. New rules 18.4. Listing rules explicitly 18.5. Sorting and indexing of rules 18.6. The preamble of a rule 18.7. New rulebooks 18.8. Basis of a rulebook 18.9. Rulebook variables 18.10. Success and failure 18.11. Named outcomes 18.12. Rulebooks producing values 18.13. Consider and abide 18.14. Procedural rules 18.15. Phrases concerning rules 18.16. Consider is not the same as follow 18.17. Two rulebooks used internally 18.18. The Laws for Sorting Rulebooks 18.19. Review of Chapter 18: Rulebooks Chapter 19: Advanced Text 19.1. Ordinary text and indexed text 19.2. Memory limitations with indexed text 19.3. Characters, words, punctuated words, unpunctuated words, lines, paragraphs 19.4. Upper and lower case letters 19.5. Matching and exactly matching 19.6. Regular expression matching 19.7. Indexed text in variables, properties and tables 19.8. Replacements 19.9. Summary of regular expression notation Chapter 20: Lists 20.1. Lists and entries 20.2. Constant lists 20.3. Saying lists of values 20.4. Testing and iterating over lists 20.5. Building lists 20.6. Lists of objects 20.7. Lists of values matching a description 20.8. Sorting, reversing and rotating lists 20.9. Accessing entries in a list 20.10. Lengthening or shortening a list 20.11. Variations: arrays, logs, queues, stacks, sets, sieves and rings Chapter 21: Advanced Phrases 21.1. A review of kinds 21.2. Descriptions as values 21.3. Phrases as values 21.4. Default values for phrase kinds 21.5. Map, filter and reduce 21.6. Generic phrases 21.7. Kind variables 21.8. Matching the names of kinds 21.9. In what order? 21.10. Ambiguities Chapter 22: Figures, Sounds and Files 22.1. Beyond text 22.2. How IF views pictures 22.3. Virtual machines and story file formats 22.4. Gathering the figures 22.5. Declaring and previewing the figures 22.6. Displaying the figures 22.7. Recorded sounds 22.8. Declaring and playing back sounds 22.9. Some technicalities about figures and sounds 22.10. Files 22.11. Declaring files 22.12. Writing and reading tables to external files 22.13. Writing, reading and appending text to files 22.14. Exchanging files with other programs Chapter 23: Releasing 23.1. The finished product 23.2. Bibliographic data 23.3. Genres 23.4. The Library Card 23.5. The Treaty of Babel and the IFID 23.6. The Release button and the Materials folder 23.7. The Joy of Feelies 23.8. Cover art 23.9. An introductory booklet 23.10. A website 23.11. A playable web page 23.12. Website templates 23.13. Advanced website templates 23.14. Republishing existing works of IF 23.15. Walkthrough solutions 23.16. Releasing the source text 23.17. Improving the index map 23.18. Producing an EPS format map 23.19. Settings in the map-maker 23.20. Table of map-maker settings 23.21. Kinds of value accepted by the map-maker 23.22. Titling and abbreviation 23.23. Rubrics Chapter 24: Publishing 24.1. Finding a readership 24.2. How a novel is published 24.3. How interactive fiction is published 24.4. The IF Archive 24.5. A Website of Its Own 24.6. IFDB: The Interactive Fiction Database 24.7. Competitions 24.8. SPAG 24.9. The Gaming Avant-Garde 24.10. The Digital Literature Community 24.11. A short concluding homily Chapter 25: Extensions 25.1. The status of extensions 25.2. The Standard Rules 25.3. Authorship 25.4. A simple example extension 25.5. Version numbering 25.6. Extensions and story file formats 25.7. Extensions can include other extensions 25.8. Extensions can interact with other extensions 25.9. Extensions in the Index 25.10. Extension documentation 25.11. Examples and headings in extension documentation 25.12. Implications 25.13. Using Inform 6 within Inform 7 25.14. Defining phrases in Inform 6 25.15. Phrases to decide in Inform 6 25.16. Handling phrase options 25.17. Making and testing use options 25.18. Longer extracts of Inform 6 code 25.19. Primitive Inform 6 declarations of rules 25.20. Inform 6 objects and classes 25.21. Inform 6 variables, properties, actions, and attributes 25.22. Inform 6 Understand tokens 25.23. Inform 6 adjectives 25.24. Naming Unicode characters 25.25. The template layer 25.26. Translating the language of play 25.27. Segmented substitutions 25.28. Invocation labels, counters and storage 25.29. To say one of Chapter 26: What's New in Inform? 26.1. Where to find new developments 26.2. What's new in build 6E59 (June 2010) 26.3. What's new in build 5Z71 (April 2009) 26.4. What's new in build 5U92 (September 2008) 26.5. What's new in build 5T18 (April 2008) 26.6. What was new in build 5J39 (December 2007) 26.7. What was new in build 5G67 (November 2007) 26.8. What was new in build 4X60 (23 August 2007) 26.9. What was new in build 4W37 (27 July 2007) 26.10. What was new in build 4U65 (27 April 2007) 26.11. What was new in build 4S08 (25 March 2007) Examples Example 1 (*): About the examples Example 2 (*): Verbosity 1 Example 3 (**): Slightly Wrong Example 4 (*): Port Royal 1 Example 5 (**): Up and Up Example 6 (***): Starry Void Example 7 (*): Port Royal 2 Example 8 (*): The Unbuttoned Elevator Affair Example 9 (*): Port Royal 3 Example 10 (*): First Name Basis Example 11 (*): Midsummer Day Example 12 (*): Tamed Example 13 (*): Disenchantment Bay 1 Example 14 (*): Replanting Example 15 (*): Disenchantment Bay 2 Example 16 (*): Disenchantment Bay 3 Example 17 (*): Disenchantment Bay 4 Example 18 (**): Laura Example 19 (*): Disenchantment Bay 5 Example 20 (**): Escape Example 21 (***): Garibaldi 1 Example 22 (*): Disenchantment Bay 6 Example 23 (**): Neighborhood Watch Example 24 (*): Disenchantment Bay 7 Example 25 (**): Down Below Example 26 (*): Peugeot Example 27 (**): Disenchantment Bay 8 Example 28 (***): Hover Example 29 (*): Disenchantment Bay 9 Example 30 (*): Belfry Example 31 (**): Gopher-wood Example 32 (*): Disenchantment Bay 10 Example 33 (*): Disenchantment Bay 11 Example 34 (***): Brown Example 35 (****): Disenchantment Bay 12 Example 36 (***): Search and Seizure Example 37 (**): Van Helsing Example 38 (**): Prisoner's Dilemma Example 39 (**): The World of Charles S. Roberts Example 40 (***): Fore Example 41 (**): Vouvray Example 42 (*): Odin Example 43 (*): Something Narsty Example 44 (***): Get Me to the Church on Time Example 45 (**): Change of Basis Example 46 (*): Would you...? Example 47 (**): Straw Boater Example 48 (*): The Undertomb 1 Example 49 (**): The Undertomb 2 Example 50 (***): Signs and Portents Example 51 (***): The Crane's Leg 1 Example 52 (***): Real Adventurers Need No Help Example 53 (***): Early Childhood Example 54 (*): Being Prepared Example 55 (**): Model Shop Example 56 (***): The Night Before Example 57 (***): U-Stor-It Example 58 (*): Bic Example 59 (***): Fallout Enclosure Example 60 (***): Ballpark Example 61 (*): Control Center Example 62 (**): Tiny Garden Example 63 (*): When? Example 64 (***): Persephone Example 65 (***): Whence? Example 66 (*): Radio Daze Example 67 (**): Camp Bethel Example 68 (**): Beekeeper's Apprentice Example 69 (*): Garibaldi 2 Example 70 (***): The Über-complète clavier Example 71 (*): Fifty Ways to Leave Your Larva Example 72 (***): Fifty Times Fifty Ways Example 73 (*): Finishing School Example 74 (***): Only You... Example 75 (**): Versailles Example 76 (***): Lean and Hungry Example 77 (*): Mistress of Animals Example 78 (*): All Roads Lead to Mars Example 79 (**): Hotel Stechelberg Example 80 (***): A View of Green Hills Example 81 (***): Unblinking Example 82 (****): Revenge of the Fussy Table Example 83 (**): Yolk of Gold Example 84 (*): Grilling Example 85 (*): Bad Hair Day Example 86 (***): Democratic Process Example 87 (****): Sand Example 88 (*): Fine Laid Example 89 (*): Hayseed Example 90 (*): Morning After Example 91 (*): Sybil 1 Example 92 (*): Lucy Example 93 (**): Sybil 2 Example 94 (***): Costa Rican Ornithology Example 95 (***): The Art of Noise Example 96 (*): Zodiac Example 97 (*): Ming Vase Example 98 (*): Beachfront Example 99 (**): Today Tomorrow Example 100 (*): Veronica Example 101 (**): A&E Example 102 (***): Polarity Example 103 (***): Bumping into Walls Example 104 (*): Mattress King Example 105 (*): No Relation Example 106 (**): One Short Plank Example 107 (***): Provenance Unknown Example 108 (***): Zorb Example 109 (*): Dearth and the Maiden Example 110 (***): Mimicry Example 111 (*): Y ask Y? Example 112 (****): A Day For Fresh Sushi Example 113 (***): Don Pedro's Revenge Example 114 (*): Politics as Usual Example 115 (***): Centered Example 116 (*): Vitrine Example 117 (*): Thirst Example 118 (*): Thirst 2 Example 119 (**): Meteoric I and II Example 120 (***): Orange Cones Example 121 (***): Terror of the Sierra Madre Example 122 (*): Beverage Service Example 123 (*): Spring Cleaning Example 124 (**): Extra Supplies Example 125 (*): Bee Chambers Example 126 (**): Hatless Example 127 (***): Technological Terror Example 128 (*): Higher Calling Example 129 (*): Do Pass Go Example 130 (*): Lanista 1 Example 131 (*): Weathering Example 132 (***): Uptown Girls Example 133 (*): Candy Example 134 (*): Zork II Example 135 (*): Clueless Example 136 (**): Mutt's Adventure Example 137 (***): No Place Like Home Example 138 (***): Big Sky Country Example 139 (***): Witnessed 1 Example 140 (****): Text Foosball Example 141 (**): IPA Example 142 (*): Situation Room Example 143 (*): MRE Example 144 (**): Totality Example 145 (**): Empire Example 146 (***): Hour of the Wren Example 147 (*): Night Sky Example 148 (***): Zero Example 149 (*): Tense Boxing Example 150 (**): Elsie Example 151 (**): Bruneseau's Journey Example 152 (*): Infiltration Example 153 (*): Annoyotron Jr Example 154 (*): Pine 1 Example 155 (**): Entrapment Example 156 (*): Age of Steam Example 157 (*): Full Moon Example 158 (**): Space Patrol - Stranded on Jupiter! Example 159 (***): Day One Example 160 (***): Bowler Hats and Baby Geese Example 161 (***): Pine 2 Example 162 (*): The Prague Job Example 163 (***): Entrevaux Example 164 (*): Night and Day Example 165 (***): Pine 3 Example 166 (***): Panache Example 167 (***): Pine 4 Example 168 (***): Cheese-makers Example 169 (*): Ahem Example 170 (**): Ferragamo Again Example 171 (**): Proposal Example 172 (*): Matreshka Example 173 (*): Princess and the Pea Example 174 (*): Numberless Example 175 (*): Wonka's Revenge Example 176 (**): Strictly Ballroom Example 177 (**): Equipment List Example 178 (*): M. Melmoth's Duel Example 179 (***): Owen's Law Example 180 (*): Witnessed 2 Example 181 (***): A Haughty Spirit Example 182 (*): Entropy Example 183 (***): The Hang of Thursdays Example 184 (*): Virtue Example 185 (***): Latris Theon Example 186 (*): The Hypnotist of Blois Example 187 (*): Police State Example 188 (**): Generation X Example 189 (*): IQ Test Example 190 (****): Boston Cream Example 191 (*): Red Cross Example 192 (***): Frizz Example 193 (***): 3 AM Example 194 (*): The Dark Ages Revisited Example 195 (**): Paddington Example 196 (***): Delicious, Delicious Rocks Example 197 (***): Noisemaking Example 198 (*): Removal Example 199 (*): Further Reasons Why All Poets Are Liars Example 200 (*): The Second Oldest Problem Example 201 (**): Puff of Orange Smoke Example 202 (***): Croft Example 203 (**): The Man of Steel Example 204 (***): Trying Taking Manhattan Example 205 (****): Under Contract Example 206 (*): Get Axe Example 207 (***): Barter Barter Example 208 (*): Reporting rules for other characters' behavior Example 209 (***): Fate Steps In Example 210 (*): Spellbreaker Example 211 (***): A point for never saving the game Example 212 (**): Carnivale Example 213 (**): Eddystone Example 214 (***): Slogar's Revenge Example 215 (*): Magneto's Revenge Example 216 (*): Waterworld Example 217 (**): Dinner is Served Example 218 (*): Flashlight Example 219 (*): Bosch Example 220 (*): Cactus Will Outlive Us All Example 221 (**): Actor's Studio Example 222 (**): Anteaters Example 223 (***): Formal syntax of sentences Example 224 (*): Interrogation Example 225 (*): Celadon Example 226 (***): Four Cheeses Example 227 (*): Transmutations Example 228 (***): Otranto Example 229 (*): Unthinkable Alliances Example 230 (***): The Unexamined Life Example 231 (*): The Abolition of Love Example 232 (*): Swerve left? Swerve right? Or think about it and die? Example 233 (*): Beneath the Surface Example 234 (***): Bogart Example 235 (***): The Problem of Edith Example 236 (*): Wainwright Acts Example 237 (***): A Humble Wayside Flower Example 238 (*): Meet Market Example 239 (***): For Demonstration Purposes Example 240 (*): Number Study Example 241 (**): Murder on the Orient Express Example 242 (**): What Not To Wear Example 243 (***): Mathematical view of relations Example 244 (***): Graph-theory view of relations Example 245 (*): rBGH Example 246 (**): Wonderland Example 247 (**): Dimensions Example 248 (***): Lead Cuts Paper Example 249 (***): Zqlran Era 8 Example 250 (***): Snip Example 251 (***): Nickel and Dimed Example 252 (*): Widget Enterprises Example 253 (*): Frozen Assets Example 254 (**): Money for Nothing Example 255 (***): Lemonade Example 256 (***): Savannah Example 257 (*): Depth Example 258 (**): Fabrication Example 259 (**): The Speed of Thought Example 260 (***): Dubai Example 261 (**): Port Royal 4 Example 262 (*): If It Hadn't Been For... Example 263 (**): Odyssey Example 264 (**): Jokers Wild Example 265 (***): Noisy Cricket Example 266 (*): Merlin Example 267 (***): Questionable Revolutions Example 268 (***): The Queen of Sheba Example 269 (***): Goat-Cheese and Sage Chicken Example 270 (**): Farewell Example 271 (**): Sweeney Example 272 (***): Introduction to Juggling Example 273 (*): Food Network Interactive Example 274 (**): Trieste Example 275 (*): XYZZY Example 276 (*): Indirection Example 277 (**): Xylan Example 278 (*): Anchorite Example 279 (*): Alpaca Farm Example 280 (****): Cloak of Darkness Example 281 (*): The Trouble with Printing Example 282 (**): Lanista 2 Example 283 (*): Shawn's Bad Day Example 284 (***): The Left Hand of Autumn Example 285 (*): Ish. Example 286 (**): Nameless Example 287 (*): Safety Example 288 (*): Tom's Midnight Garden Example 289 (**): Ibid. Example 290 (*): One of Those Mornings Example 291 (**): Actaeon Example 292 (*): Pages Example 293 (**): Down in Oodville Example 294 (***): Straw Into Gold Example 295 (*): Misadventure Example 296 (**): Safari Guide Example 297 (*): Palette Example 298 (***): Baritone, Bass Example 299 (*): Lies Example 300 (*): Aspect Example 301 (*): Hymenaeus Example 302 (**): Terracottissima Example 303 (**): Peers Example 304 (**): Channel 1 Example 305 (***): Terracottissima Maxima Example 306 (***): Tilt 1 Example 307 (***): Channel 2 Example 308 (*): Puncak Jaya Example 309 (*): Whither? Example 310 (*): Cinco Example 311 (**): Claims Adjustment Example 312 (*): Quiz Show Example 313 (**): Bibliophilia Example 314 (*): Pot of Petunias Example 315 (*): Masochism Deli Example 316 (*): Query Example 317 (*): The Gorge at George Example 318 (***): Hot Glass Looks Like Cold Glass Example 319 (*): Some Assembly Required Example 320 (***): Lakeside Living Example 321 (*): Ant-Sensitive Sunglasses Example 322 (**): AARP-Gnosis Example 323 (***): Aftershock Example 324 (***): Crusoe Example 325 (*): Hays Code Example 326 (*): Shipping Trunk Example 327 (**): Trachypachidae Maturin 1803 Example 328 (****): Chronic Hinting Syndrome Example 329 (**): Hudsucker Industries Example 330 (*): Prolegomena Example 331 (*): Unpeeled Example 332 (*): Rules of Attraction Example 333 (***): Zorn of Zorna Example 334 (**): Hohmann Transfer Example 335 (***): Four Stars Example 336 (*): Ways Out Example 337 (**): Guided Tour Example 338 (*): Reflections Example 339 (**): Emma Example 340 (****): Air Conditioning is Standard Example 341 (*): Rip Van Winkle Example 342 (**): Happy Hour Example 343 (**): The Eye of the Idol Example 344 (*): Priority Lab Example 345 (*): Low Light Example 346 (***): Casino Banale Example 347 (*): Kiwi Example 348 (***): Copper River Example 349 (*): Peeled Example 350 (*): Scope for listening different from scope for seeing Example 351 (**): Ginger Beer Example 352 (**): Rock Garden Example 353 (***): Stately Gardens Example 354 (*): Apples Example 355 (*): Originals Example 356 (***): Walls and Noses Example 357 (*): Latin Lessons Example 358 (*): Minimal Movement Example 359 (**): Fragment of a Greek Tragedy Example 360 (**): North by Northwest Example 361 (**): Cloves Example 362 (***): Complimentary Peanuts Example 363 (*): Pizza Prince Example 364 (*): The Big Sainsbury's Example 365 (***): Lollipop Guild Example 366 (*): WXPQ Example 367 (***): Xot Example 368 (*): Bikini Atoll Example 369 (*): Battle of Ridgefield Example 370 (*): Finality Example 371 (*): Jamaica 1688 Example 372 (**): Xerxes Example 373 (*): Blankness Example 374 (*): Nine AM Appointment Example 375 (**): Delayed Gratification Example 376 (*): Stone Example 377 (*): The Crane's Leg 2 Example 378 (**): Bribery Example 379 (*): Saint Eligius Example 380 (*): Verbosity 2 Example 381 (**): Slouching Example 382 (*): We Example 383 (***): Backus-Naur form for rules Example 384 (***): In Fire or in Flood Example 385 (*): Flotation Example 386 (*): Feline Behavior Example 387 (**): Kyoto Example 388 (*): Being Peter Example 389 (***): Tilt 2 Example 390 (*): Access All Areas Example 391 (*): Uptempo Example 392 (**): Lethal Concentration 1 Example 393 (**): Swigmore U. Example 394 (**): Solitude Example 395 (***): Lethal Concentration 2 Example 396 (****): Patient Zero Example 397 (*): Electrified Example 398 (*): Timeless Example 399 (**): Endurance Example 400 (**): Escape from the Seraglio Example 401 (*): Rocket Man Example 402 (*): Capital City Example 403 (*): About Inform's regular expression support Example 404 (*): Alpha Example 405 (*): Identity Theft Example 406 (*): Mirror, Mirror Example 407 (**): The Cow Exonerated Example 408 (*): Fido Example 409 (*): Igpay Atinlay Example 410 (*): Blackout Example 411 (**): Mr. Burns' Repast Example 412 (**): Northstar Example 413 (***): Cave-troll Example 414 (*): Oyster Wide Shut Example 415 (*): Robo 1 Example 416 (*): What Makes You Tick Example 417 (**): Formicidae Example 418 (***): Robo 2 Example 419 (*): Leopard-skin Example 420 (**): The Facts Were These Example 421 (*): Eyes, Fingers, Toes Example 422 (*): The Fibonacci Sequence Example 423 (*): I Didn't Come All The Way From Great Portland Street Example 424 (*): Lugubrious Pete's Delicatessen Example 425 (*): Sieve of Eratosthenes Example 426 (*): Your Mother Doesn't Work Here Example 427 (*): Circle of Misery Example 428 (*): Curare Example 429 (*): Alien Invasion Part 23 Example 430 (**): Labyrinth of Ghosts Example 431 (***): Rubies Example 432 (*): The Fourth Body Example 433 (**): The Fifth Body Example 434 (***): Flathead News Network Example 435 (*): Baedeker Example 436 (*): Port Royal 5 Example 437 (*): Bay Leaves and Honey Wine Example 438 (**): Modern Conveniences Example 439 (**): Tilt 3 Example 440 (*): Odins Example 441 (***): Pink or Blue Example 442 (*): Status line with centered text, the hard way Example 443 (*): Chanel Version 1 Example 444 (*): Blink Example 445 (**): Uncommon Ground Example 231 (*): The Abolition of Love Chapter 1: Welcome to Inform 1.1. Preface Welcome to Inform, a design system for interactive fiction based on natural language. Interactive fiction is a literary form which involves programming a computer so that it presents a reader with a text which can be explored. Inform aims to make the burden of learning to program such texts as light as possible. It is a tool for writers intrigued by computing, and computer programmers intrigued by writing. Perhaps these are not so very different pursuits, in their rewards and pleasures: The sheer joy of making things... the fascination of fashioning complex puzzle-like objects of interlocking moving parts and watching them work in subtle cycles... the delight of working in such a tractable medium. The programmer, like the poet, works only slightly removed from pure thought-stuff. He builds his castles in the air, from air, creating by exertion of the imagination. (Frederick P. Brooks, "The Mythical Man-Month", 1972) Writing with Inform is one of two interlinked books included with Inform: a concise but complete guide to the system. The other book is The Inform Recipe Book, a comprehensive collection of examples, showing its practical use. If you are reading this within the Inform application, you will see that the Writing with Inform pages are on "white paper", while the Recipe Book is on "yellow paper". These notes are arranged so that the reader can, in principle, write whole works of fiction as early as the end of Chapter 3. Each subsequent chapter then extends the range of techniques available to make livelier and more intriguing situations. For the benefit of partially sighted users, duplicate versions of this book in plain text and lightly-formatted HTML formats can be found at the Inform website. This new release of Inform ("Inform 7", the seventh major version since 1993) is a radical departure from most previous approaches to interactive fiction. In particular, it is very different from Inform 6, which newcomers will not need to know anything about. Inform 6 sits inside Inform 7, and is part of the inner workings, but is not visible from the outside. For information about Inform 6, see www.inform-fiction.org. Programming is best regarded as the process of creating works of literature, which are meant to be read... so we ought to address them to people, not to machines. (Donald Knuth, "Literate Programming", 1981) (See Acknowledgements for a chance to try out the cross-referencing links in Writing with Inform - click on the red asterisk or the name of the destination to go there.) Example 1 (*): About the examples An explanation of the examples in this documentation, and the asterisks attached to them. Click the heading of the example, or the example number, to reveal the text. 1.2. Acknowledgements I should like to dedicate this new edition of Inform to Emily Short and Andrew Plotkin, whose shrewd and sceptical suggestions made a contribution which can hardly be overstated. A long email correspondence with Andrew entirely subverted my original thoughts about natural-language IF, as he convinced me that the "new model" of rule-based IF was a truer foundation; while Emily's wry, witty analysis and how-about-this? cheered me at low moments, besides providing the impetus and often the specifics for a lot of the best ideas. Among those who kindly gave up great swathes of time to test, and think about, the early Inform 7, I must give special thanks to Sonja Kesserich, who was so often patient, and so often right. Her easy-going "pestering" (Sonja's word) led to improvements more or less everywhere, at a time when using Inform 7 was not much fun. I also thank David Cornelson for gathering volunteers; and I thank them, too. From the outset, I have thought of Inform 7 as no longer being a command-line compiler, but a compiler in combination with a radically more humanising user interface: all credit for the reference implementation under Mac OS X belongs to Andrew Hunter. I thank him for his forbearance in the face of much cajolery. How simple the metaphor of an interactive book with facing pages may seem, but the coding was an enormous challenge, and I could not have done it. Though David Kinder's Windows implementation of the user interface does indeed visually follow Andrew's original, the two programs were coded independently, and the programming task taken up by David was formidable indeed. He also uncovered numerous bugs in the compiler which, through one coincidence or another, did not reveal themselves under OS X. Philip Chimento's Gnome-based user interface for Linux became officially part of the project in November 2007, when the first easy-to-install packages for Ubuntu and Fedora were offered. Philip's efforts were particularly generous since the early stages of Inform-for-Linux were so tentative: for many months, we weren't sure how to go about the project, and during that time Philip quietly wrote us a solution. The final months before the Public Beta release of Inform 7 were made more enjoyable, as well as more productive, by fruitful discussions leading to a cross-platform standard for bibliographic data and cover art. I would like to thank L. Ross Raszewski, who wrote frighteningly efficient reference software in frighteningly little time; the librarians of the IF-Archive, Andrew Plotkin, David Kinder and Paul Mazaitis; and my fellow authors of IF design systems - Mike Roberts (of the Text Adventure Development System); Kent Tessman (of Hugo); and Campbell Wild (of ADRIFT). The iconography of Roman mosaics introduced in the June 2010 build of Inform is indebted to artists and craftsmen of whom nothing can be known, except for a few guesses about which workshop undertook which mosaic panel. But we can at least thank some photographers: Nevit Dilmen for the famous Gypsy Girl of Zeugma, now in the Gaziantep Museum of Archeology, Turkey; Mary Harrsch for her excellent photographs of the Orpheus mosaic now in the Dallas Museum of Art, and for images of mosaics from Pompeii now in the Museo Archaeologico Nazionale di Napoli; and Alberto Fernandez Fernandez for a mosaic from a villa in Centocelle, near Rome. And also thank English Heritage, for looking after the Roman villa at North Leigh, Oxfordshire, among quite a lot else. The North Leigh mosaic floor provides the incomplete and complete snapshots used on the Problems panel. 1.3. The facing pages (Mac OS X only) This Public Beta of Inform 7 runs on Mac OS X through the graphical user interface created by Andrew Hunter. (Windows only) This Public Beta of Inform 7 runs on Windows through the graphical user interface created by David Kinder. (Linux only) This Public Beta of Inform 7 runs on Linux through the text-only interface created by Adam Thornton. (Gnome only) This Public Beta of Inform 7 runs on Linux through the graphical user interface created by P. F. Chimento. (Mac OS X only) The main window is an opened book showing two facing pages, and as we shall see it behaves as if these pages are in dialogue with each other: for the most part we write on the left hand page and see responses appear on the right. But all is controllable. The margin between the two pages can be dragged back and forth like the slide on a trombone: each page can be made smaller that the other may grow larger. Moreover, each page can display one of a number of displays relevant to the current project, called "panels", one of them being the Documentation panel which displays this manual. The vertical strip of choices at the right hand margin of each page allows you to choose between panels. (The same panel can be showing on both pages at the same time, if that's useful.) (Windows only) The main window is an opened book showing two facing pages, and as we shall see it behaves as if these pages are in dialogue with each other: for the most part we write on the left hand page and see responses appear on the right. But all is controllable. The margin between the two pages can be dragged back and forth like the slide on a trombone: each page can be made smaller that the other may grow larger. Moreover, each page can display one of a number of displays relevant to the current project, called "panels", one of them being the Documentation panel which displays this manual. The horizontal strip of choices at the top of each page allows you to choose between panels. (The same panel can be showing on both pages at the same time, if that's useful.) (Linux only) The interface is extremely crude compared to that available on Mac OS X or Windows. The panels that exist are accessible via menu options, and anywhere you see reference to a button, it simply doesn't exist. Go and Release are implemented, as is Compile, which rebuilds the story but does not start it. There is a further settings panel available to you, the IDE settings, which allows you to control which editor you wish to use to edit your project, which browser allows you to view HTML files, which interpreters to use to play your stories, and whether or not these should be run in the background. Users with a graphical desktop are likely to want to choose the background option, while those running only with text terminals will not. To select an option, type the letter indicated on the screen and follow it with the Enter key. (Gnome only) The main window is an opened book showing two facing pages, and as we shall see it behaves as if these pages are in dialogue with each other: for the most part we write on the left hand page and see responses appear on the right. But all is controllable. The margin between the two pages can be dragged back and forth like the slide on a trombone: each page can be made smaller that the other may grow larger. Moreover, each page can display one of a number of displays relevant to the current project, called "panels", one of them being the Documentation panel which displays this manual. The horizontal strip of choices at the top of each page allows you to choose between panels. (The same panel can be showing on both pages at the same time, if that's useful.) At the start the only panels available are a blank space in which to write the first lines of a new interactive fiction - the Source panel - and this one, the Documentation. Clicking on the other choices will do nothing. The exception is the Settings panel, which contains some preference settings for the individual project - not the whole application. This is always available, but it controls settings which can be left alone almost all of the time. 1.4. The Go! button Clicking the Go button translates the text in the Source panel into a computer program which enacts the interactive fiction, and automatically sets it going (in the Game panel, which opens as needed). If the Source is empty of text, Inform will be unable to create anything: it needs at least one name of a location where the drama can unfold. For reasons of tradition, such locations are normally called "rooms", though people have used them to represent anything from grassy fields to states of mind and other metaphorical places. "Midsummer Day" The Gazebo is a room. Clicking Go with this text in the Source panel will result in a short delay, after which the Game panel will appear, from which we can explore this newly created world: an interactive fiction called "Midsummer Day". It will not be very exciting, since Inform has only five words to go on, but we can add more detail to the source at any point and then click Go again to try out the changes. (Note that there is no need to "quit" these explorations in the Game panel. When Go is clicked, any game already in progress is discarded in favour of the new version.) (Mac OS X only) Typing Command-R has the same effect as clicking Go. If Inform is running on Mac OS 10.3.9 or later, clicking on a "text" icon (Image paste.png here) in this documentation copies the example text which follows it into the Source as if you had faithfully typed it out. (This icon is usually provided only for fairly long examples, but note that you can in fact copy and paste any text from this documentation into the source by selecting it with the mouse, typing Command-C, then clicking to a position in the source and typing Command-V.) (Windows only) Typing F5 has the same effect as clicking Go. Clicking on a "text" icon (Image paste.png here) in this documentation copies the example text which follows it into the Source as if you had faithfully typed it out. (This icon is usually provided only for fairly long examples, but note that you can in fact copy and paste any text from this documentation into the source by selecting it with the mouse, typing Ctrl-C, then clicking to a position in the source and typing Ctrl-V.) (Linux only) Typing "G" is the only way you can perform the Go action. (Gnome only) Typing Ctrl-R has the same effect as clicking Go. Clicking on a "text" icon (Image paste.png here) in this documentation copies the example text which follows it into the Source as if you had faithfully typed it out. (This icon is usually provided only for fairly long examples, but note that you can in fact copy and paste any text from this documentation into the source by selecting it with the mouse, typing Ctrl-C, then clicking to a position in the source and typing Ctrl-V.) 1.5. The Replay button Replay works identically to Go, except that it does something further: once the game is created, it automatically plays through the same commands as were typed into the previous version. For instance: suppose we click Go to bring Midsummer Day into being, and find ourselves playing the game. We type "look" and find that there is not much to see. Going back to the source, we add "A white canvas parasol raised up on stakes driven into the grass." so that the source now reads "Midsummer Day" The Gazebo is a room. "A white canvas parasol raised up on stakes driven into the grass." Instead of clicking Go, we click Replay, and can sit back and watch what has changed. In this example, it only saves us the trouble of typing "look", but once games become long and elaborate, Replay is invaluable: and especially when we notice in play that something very minor is wrong - a spelling error, say - and want to fix it immediately, without fuss. (Linux only) Replay is not implemented in the text-mode Linux interface. 1.6. The Index and Errors panels If, when Go! is clicked, the text in the Source panel is not fully understood, then Inform will generate a report of the problems it found, which will open in the "Errors" panel. (Other information is also available in "Errors", but most of it is used for debugging Inform, and can be ignored.) On the other hand, if the text was fully understood then another new panel will become available: the "Index". This is a cross-referenced index of the source, or rather, of the interactive fiction which has been generated. The Index is only an optional convenience, but becomes more and more helpful as the fiction grows larger. Its exact format does not matter for now. The icon (Image Reveal.png here) always denotes a reference to a particular line in the Source text, that is, to something written in the source: clicking it opens the Source panel and jumps to that position. The icon (Image Below.png here) indicates that more detailed information can be read further down the text in the same panel: clicking it jumps down to this more detailed report. Lastly, the icon (Image help.png here) hints that there is a relevant page of this manual: clicking this opens the Documentation panel and switches to it. (Linux only) The Index is accessible by typing "I" at the prompt, if you have set your browser. You can set the browser by typing "S" to get to the settings panel, and then "I" for the IDE panel. From the top-level Index you will be able to access Errors as well as other information. 1.7. The Skein The Replay button demonstrates that Inform must be quietly remembering the commands typed into the last run through the game. In fact it remembers, and automatically organises, every previous run. Inform's approach to testing interactive fiction is to treat it as being like the analysis of other turn-based games, such as chess. It would be prohibitively difficult to work out every possible combination of moves: instead, we analyse those which go somewhere, and look for significant choices. Every Queen's Gambit begins with the same first three moves (1. d4, d5; 2. c4), but then there is a choice, as the next move decides whether we have a Queen's Gambit Accepted (dxc4) or Declined (e6). Books about chess often contain great tables of such openings, which run together for a while but eventually diverge. To learn chess, one must explore all of these variations. Inform's Skein panel is just such a table, built automatically. If we think of the list of typed commands as a thread, then the skein is (as the name suggests) braided together from all these threads. In the display, time begins at the top, with the start knot, and the threads of different games hang downwards from it. Double-clicking on a command translates the source afresh and replays the game from start down to that command, and then stops. We are then free to continue play by typing commands into the Game panel, of course, and these commands will automatically be recorded in the Skein as a new variation of play, diverging from the previous threads. (Linux only) The Skein is not implemented in the Linux version. 1.8. A short Skein tutorial In the following example, we will see how the Skein is woven as different commands are tried. As it happens, the game being played is the example "Witnessed", from Chapter 11, but the details do not matter. When the project has never been played at all, if we switch to the Skein panel (or open it opposite the Game panel) we will only find this: (Image skt1.png here) Suppose we click Go for the first time and type two commands in: TURN ON ALARM and then LOOK. Now the Skein shows: (Image skt2.png here) Only one line of play is known to Inform, and it runs downwards in a thread from the special "- start -" knot, which represents the situation before any command has been tried. The useful thing about having past histories recorded like this is that we can revisit them. Suppose we want to go back to the situation after typing only TURN ON ALARM. We could click Go again and type that first command in once more, but now we have an easier method: we simply double-click on the TURN ON ALARM knot. The game restarts by itself, and commands are automatically keyed in to regain the position of play represented by the knot we clicked on - in this example that only keys a single command in, but it might have been hundreds. The Skein now looks like this: (Image skt3.png here) All knots are displayed either as yellow or green. Yellow knot are the ones in the history of the game currently playing. The LOOK knot is green because it hasn't happened in the current game yet - and in fact, it won't happen in the current game, because instead we play TURN ON METER. Now the Skein changes again: (Image skt4.png here) Inform now knows about two ways to play the current project: one consisting of TURN ON ALARM and then TURN ON METER, the other of TURN ON ALARM and then LOOK. Since these only differ after the first turn, Inform displays them as a thread which divides into two after the first turn. Again, LOOK remains green because it hasn't been played in the current game. Note also that one of the two possible threads here is drawn more thickly (here it is shown with thick dashes rather than thin). Only one thread is ever drawn thickly -- the one currently being shown in the Transcript panel, which we will come to later on. (That often corresponds to the current line of play, as now, because the Transcript follows what we do unless we choose otherwise.) After a little more exploration, we reach the following: (Image skt5.png here) (Mac OS X only) At this point we decide that we want to preserve the thread leading to EXAMINE CHIMES - perhaps it's a sequence we are going to want to test often. The Skein can be edited very easily, in several ways (for instance clicking and holding on a command allows us to edit the text of the command): control-clicking (or right-clicking) on a knot brings up a contextual menu. On Mac OS X, some popular knot controls appear whenever the mouse hovers over the knot, like so: (Windows only) At this point we decide that we want to preserve the thread leading to EXAMINE CHIMES - perhaps it's a sequence we are going to want to test often. The Skein can be edited very easily: right-clicking on a knot brings up a contextual menu. (Mac OS X only) (Image skt6.png here) (Mac OS X only) We click on the padlock button (or choose Lock This Branch from the contextual menu), and this makes the thread through to here "locked". That means the knots can't be deleted (unless we unlock them again) - either by our own mistake, or by Inform trimming back no-longer-needed threads of the Skein to keep it manageable in size. (Windows only) We choose Lock This Thread from the contextual menu, and this makes the thread through to here "locked". That means the knots can't be deleted (unless we unlock them again) - either by our own mistake, or by Inform trimming back no-longer-needed threads of the Skein to keep it manageable in size. (Image skt7.png here) Note that this locked history is now drawn as a solid thread, whereas all the others are unlocked and drawn as dashes. Now we have a securely remembered piece of standard play: it means we can try out the sequence TURN ON ALARM / TURN ON METER / WAIT / EXAMINE CHIMES any time we want to with a double-click on the final knot. This is convenient for testing - but so far it only runs the test: to see whether the test came out well or badly, we have to look through what happened, perhaps by scrolling back in the Game panel to look at the text. And that means that we need to remember what the text should have been like. In fact, though, Inform can remember for us, using the Transcript panel. This is closely joined to the Skein panel, and it's often convenient to flip between the two. Turning to the Transcript now, we find a two-column view of the game currently being played. The left-hand column shows the text which has been displayed on each turn so far; the right-hand column is empty. The bottom of the Transcript looks like so: (Image skt8.png here) The empty right-hand column displays the "blessed" transcript - one which the author has approved as being correct. This can be done for each individual knot, using the Bless button joining the columns, but in this case we will bless the whole transcript of this game, using the Bless All button. Now there's text in both columns, and of course the two columns match. (Note that the blessed transcript is in a brighter colour.) (Image skt9.png here) Back in the Skein, we find that the knots which have transcripts have lit up, and are brighter than the others. If we Go, to start a new game, and then look at the Skein: (Image skt10.png here) we see that the knots for which we have blessed a transcript are in a brighter green (or a brighter yellow, if they're in the current game being played). Now suppose we change the source text for the project, so that we make it behave differently. The details don't matter, but suppose we do something which changes the result of the TURN ON METER command, and then run the test again. Now we find: (Image skt11.png here) The red warning badge on the TURN ON METER knot alerts us that the last time this knot was tried (just now, as it happens), the resulting text didn't agree with its blessed transcript. (Red badges can only be seen on bright-coloured knots which have transcripts - for other knots, there's nothing to compare with.) On the other hand, the rest of the yellow current line of play worked out exactly the same as we expected - so no badges. Clicking on the red badge takes us into the Transcript panel at the right place, where the corresponding turn's transcript has also turned red: (Image skt12.png here) (Mac OS X only) Again, what actually happened is on the left; what should have happened is on the right. The change is shown with underlining - we added the text "quivers, then". If we approve this change, by clicking on the Bless button for the red turn, the amended text will become the correct text to compare against in future runs, and the turn will become green to show that once again all is well. (We can also edit the blessed transcript directly, by clicking in the text and typing.) Clicking on the Show knot button takes us back in the skein, at the right place: where we will see that the red warning badge has disappeared. (Windows only) Again, what actually happened is on the left; what should have happened is on the right. The change is shown with underlining - we added the text "quivers, then". If we approve this change, by clicking on the Bless button for the red turn, the amended text will become the correct text to compare against in future runs, and the turn will become green to show that once again all is well. (We can also edit the blessed transcript directly, by double-clicking in the text and typing.) Clicking on the Show knot button takes us back in the skein, at the right place: where we will see that the red warning badge has disappeared. Some writers of IF like to work backwards from a transcript of the game they want to produce, and for them, the Skein and Transcript combination will be helpful as a running picture of what works so far. Other authors may not use the Skein/Transcript feature at all until right at the end of a project, in testing before publication, when it becomes very important to be able to make small changes in one area without upsetting everything else. Either way, the Skein and Transcript together make a very powerful testing aid. (Mac OS X only) This tutorial has shown only a short line of play, to keep the pictures small, but for a large project the Skein might run to thousands of knots. It then becomes important to be able quickly to find key knots corresponding to plot developments. To help with that, we can annotate certain knots with any label we choose (using one of the mouseover buttons, for instance): (Windows only) This tutorial has shown only a short line of play, to keep the pictures small, but for a large project the Skein might run to thousands of knots. It then becomes important to be able quickly to find key knots corresponding to plot developments. To help with that, we can annotate certain knots with any label we choose (by selecting Add Label from the contextual menu): (Image skt13.png here) And this is where the "Labels" gadget at the top of the Skein comes into its own: (Image skt14.png here) since it offers a menu of all the labels in the Skein, and if selected will jump to the one chosen. (Mac OS X only) The Skein has other abilities too, best explored by experimenting. For instance, we can edit the commands by clicking and holding on the command text in a knot. We can add new knots in the middle of existing lines using the "add knot" mouseover button. The Play All Blessed option (on the Build menu in OS X) is especially powerful: it tests each possible blessed history in turn, trying all of them, and can therefore test very complicated multiple endings and the like in a single click. (Windows only) The Skein has other abilities too, best explored by experimenting. For instance, we can edit the commands by selecting Edit Knot from the contextual menu, and we can add new knots in the middle of existing lines using the Insert Knot item on that menu. The Play All Blessed option (on the Game menu) is especially powerful: it tests each possible blessed history in turn, trying all of them, and can therefore test very complicated multiple endings and the like in a single click. (Linux only) The Skein and Transcript are not implemented in the Linux version. (Gnome only) The Transcript is not implemented in the Gnome Linux version. 1.9. Summary of the Skein and Transcript The Skein records the history of different plays through the current project, and the Transcript records the text of each response, comparing it with a "blessed" or correct version if one is available. In the Skein each typed command is a "knot". The threads hanging down from the top "- start -" knot are possible histories. Double-click on a knot to play through to there. Yellow knots are commands played so far in the current game: green knots are possible lines not taken, or not taken yet. A solid thread is "locked" and protected from deletion (by accident or when Inform trims away loose ends): a dashed thread has no such protection. A bright knot has a blessed transcript: a darker knot is one which has no blessed transcript. When a bright knot shows a red badge, this means that when last tested its command produced a textual reply which wasn't the same as the blessed transcript. Clicking on the badge shows exactly how. The thicker thread in the Skein shows the history currently being displayed in the Transcript panel. (Linux only) The Skein and Transcript are not implemented in the Linux version. (Gnome only) The Transcript is not implemented in the Gnome Linux version. 1.10. The Inspector (Mac OS X only) The Inspector window on the Mac OS X interface for Inform is a small separate panel providing additional features designed for use with Inform 6 projects, which this manual does not talk about. On other platforms (notably Windows and Linux), Inform is not designed to support Inform 6, and therefore does not have an Inspector window. (Windows only) The Inspector window on the Mac OS X interface for Inform is a small separate panel providing additional features designed for use with Inform 6 projects, which this manual does not talk about. On other platforms (notably Windows and Linux), Inform is not designed to support Inform 6, and therefore does not have an Inspector window. (Linux only) The Inspector window on the Mac OS X interface for Inform is a small separate panel providing additional features designed for use with Inform 6 projects, which this manual does not talk about. On other platforms (notably Windows and Linux), Inform is not designed to support Inform 6, and therefore does not have an Inspector window. (Gnome only) The Inspector window on the Mac OS X interface for Inform is a small separate panel providing additional features designed for use with Inform 6 projects, which this manual does not talk about. On other platforms (notably Windows and Linux), Inform is not designed to support Inform 6, and therefore does not have an Inspector window with all the features of the Mac OS X interface. (Mac OS X only) The Inspector window is a small separate panel which contains a number of useful ways to look into the project - to inspect it, in fact. This is not the place to document everything the Inspector does, because many of its features are designed for use with Inform 6 ("I6") projects, which this manual does not talk about: what this manual calls Inform is Inform 7 ("I7"). For the same reason, it is not normally open for I7 projects, but can be opened from the Window menu, and its palette of utilities can be selected from the Preferences. (Gnome only) The Inspector window is a small separate panel which contains a number of useful ways to look into the project - to inspect it, in fact. This is not the place to document everything the Inspector does, because many of its features are designed for use with Inform 6 ("I6") projects, which this manual does not talk about: what this manual calls Inform is Inform 7 ("I7"). For the same reason, it is not normally open for I7 projects, but can be opened from the Window menu, and its palette of utilities can be selected from the Preferences. (Mac OS X only) Project Files - I7 projects generally keep their source text in a single file organised internally with headings and subheadings: whereas older I6 projects organised their sources by cutting them into numerous separate files. This panel allows us to switch between those source files, so although it is an essential tool for I6 users, I7 users can leave it closed. (Mac OS X only) Notes - A place where we can type any aides-memoires, notes to ourselves about what to do next, etc.: a sort of scratchpad associated with the project. (Gnome only) Notes - A place where we can type any aides-memoires, notes to ourselves about what to do next, etc.: a sort of scratchpad associated with the project. (Mac OS X only) Index - A contents page for the project, listing all its headings and subheadings. Clicking on one jumps the source panel to the relevant point in the source. While you can see a fuller list of contents from the Contents tab of the Index pane in the main window, this is more concise and may be convenient to keep open, especially if you have a wide screen. (Gnome only) Index - A contents page for the project, listing all its headings and subheadings. Clicking on one jumps the source panel to the relevant point in the source. While you can see a fuller list of contents from the Contents tab of the Index pane in the main window, this is more concise and may be convenient to keep open, especially if you have a wide screen. (Mac OS X only) Skein - A more condensed view of the same Skein shown in the main window panel. (Seeing it here allows us to have this open at the same time as two different panels are open on the main window, and it takes less screen space here.) (Mac OS X only) Watch Expressions - Part of the I6 source-level debugger, so not useful for I7 projects. (Mac OS X only) Breakpoints - Ditto. (Mac OS X only) Search Files - This searches not only the source code, but also the documentation and even the extensions for all references to given text. Search results are produced in a fresh window and clicking on each result jumps the source (or the documentation) there. For instance, searching for "stegosaurus" will almost always bring us to the present page, which is the only one in the documentation containing that word. (Gnome only) Search Files - This searches not only the source code, but also the documentation and even the extensions for all references to given text. Search results are produced in a fresh window and clicking on each result jumps the source (or the documentation) there. For instance, searching for "stegosaurus" will almost always bring us to the present page, which is the only one in the documentation containing that word. Chapter 2: The Source Text 2.1. Creating the world Designing an interactive fiction can be divided into two related activities. One is the creation of the world as it appears at the start of play: where and what everything is. The other is to specify the rules of play, which shape how the player interacts with that initially created world. A new Inform project is void and without form, so to speak, with nothing created: but it starts with hundreds of standard rules already in place. The same division between creating things, and laying down rules, is visible in Inform source text. The creation of the world is done by making unconditional factual statements about it. For example, The wood-slatted crate is in the Gazebo. The crate is a container. Inform calls sentences like these "assertions". The verb is always written in the present tense (thus the crate "is", not "will be"). Further examples are: Mr Jones wears a top hat. The crate contains a croquet mallet. The words "is", "wears" and "contains" are forms of three of the basic verbs built in to Inform. There are only a few built-in assertion verbs, of which the most important are to be, to have, to carry, to wear, to contain and to support. (As we shall see, further assertion verbs can be created if needed.) The world described by these assertions is the starting condition of the game: what happens when play begins is another matter. If somebody picks up the crate and walks off with it, then it will no longer be in the Gazebo. Mr Jones may remove his hat. 2.2. Making rules The other kind of sentence tells Inform what should happen in certain circumstances, and reads like an instruction issued to someone: Instead of taking the crate, say "It's far too heavy to lift." This is a "rule", and it changes the crate's behaviour. The player who tries typing "take crate", "pick up the crate" or similar will be met only with the unhelpful reply "It's far too heavy to lift." The many different kinds of thing which the player can do are called "actions", and are always written as participles: "taking ...", for instance, or "putting ... on ...". Inform is built on a mass of several hundred rules, some quite complex, and it could even be said that Inform is that mass of rules. We never see the complexity behind the scenes because the whole aim is to provide a basic, penny-plain, vanilla flavoured sort of realism. It would be surprising if one could put the crate inside itself, so a rule exists to forbid this. It would be surprising if one could drop something which was already on the ground, and so on. These basic rules of realism are the ones which every new Inform project starts with. A rule always starts with a situation which it applies to, and then follows with one or more things to do. Here's an example where the situation is "Before taking the crate" - the player is just starting to try to pick the box up - and there's a three-step process to follow, but steps 2 and 3 happen only if step 1 comes out in a particular way: Before taking the crate: if the player is wearing the hat: now the hat is in the crate; say "As you stoop down, your hat falls into the crate." The steps to follow here are called "phrases". Inform knows about 400 built-in phrases, but most of them are needed only occasionally. These three are used over and over again: if tells Inform to do something only if some "condition" holds, here "the player is wearing the hat"; now tells Inform to change the situation, here so that the hat moves to the crate; and say tells Inform to say something, that is, to write some text for the player to read. Every one of the built-in phrases has a definition somewhere in this book. Here is the first to appear - first because it is the single commonest phrase people use, and also the easiest to define:

say "text"
This phrase writes out the given text for the player to read. Normally it is simply shown on screen, not spoken aloud, unless software adapted for partially sighted people is being used.
These definitions are all linked to in the Phrasebook page of a project's Index. 2.3. Punctuation An example rule from the previous section demonstrates one of Inform's conventions about punctuation, and is worth pausing to look at again. Instead of taking the crate, say "It's far too heavy to lift." In English grammar, it's usual to regard a full stop as closing its sentence even when it occurs inside quotation marks, provided there is no indication to the contrary, and this is also the rule used by Inform. Thus: The description is "Shiny." It is valuable. is read as equivalent to The description is "Shiny.". It is valuable. Sentence breaks like this occur only when the final character of the quoted text is a full stop, question mark or exclamation mark (or one of these three followed by a close bracket) and the next word begins, in the source code, with a capital letter. A paragraph break also divides sentences, behaving as if it were a full stop. Material in square brackets [like so] is "comment", in computing jargon: it is considered as being an aside, a private note by the author, and not read in by Inform. This allows us to make notes to ourselves like so: The China Shop is a room. [Remember to work out what happens if the bull gets in here!] Inform is all about text, so pieces of text are often quoted in Inform source. This example is typical: The description is "Shiny." It is valuable. Quotations always use double-quotation marks, which aren't part of the text. So the description here is just the five letters and full stop in between the marks: Shiny. That seems straightforward, but there are three conventions to watch out for. 1. Square brackets [ and ] inside quoted text don't literally mean [ and ]. They're used to describe what Inform should say, but in a non-literal way. For example, "Your watch reads [time of day]." might produce Your watch reads 9:02 AM. These are called "text substitutions". They're highly flexible, and they can take many different forms. 2. Single quotation marks at the edges of words are printed as double. So: "Simon says, 'It's far too heavy to lift.'" produces Simon says, "It's far too heavy to lift." 3. Texts which end with sentence-ending punctuation - full stop, question mark, exclamation mark - are printed with a line break after them. So: say "i don't know how this ends"; say "I know just how this ends!"; would come out quite differently - this doesn't affect the appearance of the text, but only the position where the next text will appear. These three punctuation rules for texts feel very natural with practice, and Inform users sometimes don't realise the third rule is even there, because it just seems the right thing to happen. But occasionally the rules get in the way of what we want to do. (For instance, how do we get a literal [ or ]? What if we want a single quote mark where Inform thinks we want a double, or vice versa?) So we'll come back to these rules in more detail in the chapter on Text. Inform also reads other punctuation marks. Colon ":" and semicolon ";" turned up in the previous section, in the writing of rules. It also has the more exotic "|" (not a capital I, a vertical stroke) for paragraph breaks, but people hardly ever need this. As these examples begin to show, Inform source imitates the conventions of printed books and newspapers whenever there is a question of how to write something not easily fitting into words. The first example of this is how Inform handles headings, but to see why these are so useful we first look at Problems. (See How Inform reads quoted text for a fuller exploration of the punctuation rules for text.) 2.4. Problems The language used in the source reads as if it were English aimed at a human reader (and this is intentional: the designer, after all, is a human reader and needs to be able to understand his or her own source), but in reality Inform can only understand a very modest range of sentences and will complain if its limits are passed. Subtler problems arise if the source contains contradictions. For instance, the following "Problem" might be produced: Problem. You wrote 'A starting pistol is in the cup' (Image Reveal.png here), but in another sentence 'A Panama hat is on the cup' (Image Reveal.png here): the trophy cup cannot both contain things and support things, which is what you're implying here. If you need both, the easiest way is to make it either a supporter with a container attached or vice versa. For instance: 'A desk is here. On the desk is a newspaper. An openable container called the drawer is part of the desk. In the drawer is a stapler.' This is a rather discursive error message, and if a similar problem were to occur in the same run through, it would be curtailed to: Problem. You wrote 'A firing pistol is in the box' (Image Reveal.png here), but in another sentence 'A fedora hat is on the box' (Image Reveal.png here): again, the croquet box cannot both contain things and support things. 2.5. Headings (Mac OS X only) Once the source grows beyond 1000 words or so, it can all too easily become disorganised, and by the time it reaches the size of a novella it can be difficult to find things (though the Mac OS X user interface provides a Find function, Command-F). (Windows only) Once the source grows beyond 1000 words or so, it can all too easily become disorganised, and by the time it reaches the size of a novella it can be difficult to find things (though the Windows user interface provides a Find function, Ctrl-F). (Linux only) Once the source grows beyond 1000 words or so, it can all too easily become disorganised, and by the time it reaches the size of a novella it can be difficult to find things (though nearly all editors provide a Find function). Inform provides for us to organise the source code in just the way that a printed book would be organised: with headings and subheadings. Firstly, we can put the title at the top. If the first paragraph consists only of a single quoted piece of text, then that's the title; and an author can also be given, as follows: "Spellbreaker" by Dave Lebling We will later see that more bibliographic information can also be placed here, in the same way that the imprint page of a novel comes before the text gets going. The author's name can normally be given without quotation marks, so long as it contains no punctuation. For instance: "Three Men in a Boat" by "Jerome K. Jerome" needs quotes as otherwise the full stop after the K will be mistaken for the end of a sentence. A sentence which is the only one in its paragraph and which begins with any of the words "volume", "book", "part", "chapter" or "section" is considered to be a heading or a sub-heading. It must not contain a typed line break, and in order to stand alone in its paragraph there should be a skipped line both before and after it. For instance: Section 2 - Flamsteed's Balloon Headings can be written in any format, provided they start with one of the five indicator words, and they are hierarchical: a "Part ..." heading is considered more significant than a "Chapter ..." heading but not so significant as a "Book ..." heading, and so on. (We do not need to use all five kinds of heading.) 2.6. Why using headings is a good idea Reports of problems, as we have seen, often quote back the source to justify themselves. Rather than quoting line numbers ("Midsummer Day, line 2017" or something similar) Inform uses the (Image Reveal.png here) icon. The down side of this is that a glance at the list of problems might give little hint of whereabouts in the source the difficulties lie. Inform therefore makes use of headings to give a general indication: In Part the First, Chapter 1 - Attic Area: Problem. You wrote 'South of the Attic is the Winery' (Image Reveal.png here), but in another sentence 'South of the Attic is the Old Furniture' (Image Reveal.png here): this looks like a contradiction, which might be because I have misunderstood what was meant to be the subject of one or both of those sentences. In Chapter 2 - Deeper In: Problem. You wrote 'The Disused Observatory is south of the Dark Room' (Image Reveal.png here), but in another sentence 'South of the Dark Room is the Cupboard' (Image Reveal.png here): again, this looks like a contradiction. Secondly, headings are used in the Contents tab of the Index, and are also displayed in the Inspector window of the Mac OS X Inform application: in both cases they allow rapid navigation through the source, by jumping to any heading or subheading with a single click. Finally, headings are used when working out what a name refers to. Suppose the source contains both a "four-poster bed" and also a "camp bed", and we write something like "The pillow is on the bed." Inform decides which bed is meant by giving priority to whichever is defined in the current section, or failing that the current chapter, or current part, or current book, or finally the current volume. This allows us to write, for instance, The four-poster bed is in the Boudoir. The pillow is on the bed. and not have the pillow mysteriously turn up on the camp bed, which hasn't been mentioned since way back in Chapter 2. 2.7. The SHOWME command Problem messages are generated when the source text does not make sense to Inform. Even if it does make sense, though, there is no guarantee that it does what the author intends, and the only way to find out is to test the result by playing through it (or asking others to). For the most part one plays as if one were the eventual reader of the work, but sometimes it is highly convenient to have the god-like powers which are an author's prerogative. These are provided by the testing commands, which are present at every stage until the final release version (generated by the Release button). They will be introduced in this manual as they become relevant: here is the first. (Testing command) The testing command SHOWME prints out a brief summary about a room or thing, and any contents or parts it may have. Typing SHOWME on its own shows the current room, but any item or room in the game, however distant, can be named instead. For instance: >showme Boudoir - room four-poster bed - supporter yourself - person pillow >showme diamonds diamonds - thing location: in the strongbox on the dresser in the Drawing Room unlit; inedible; opaque; portable; singular-named; improper-named description: The diamonds glitter dangerously. printed name: diamonds Much of this can be seen, and seen more easily, in the World tab of the Index panel: but that only shows the initial state of play, whereas the SHOWME command reveals the situation in mid-game. ("Room", "supporter" and so on are kinds, of which more in Chapter 3.) 2.8. The TEST command The only way to thoroughly test a work of IF is to run a complete solution through it, and carefully check the resulting transcript of dialogue. The Skein and Transcript tools of the Inform application are provided for exactly this purpose. All the same, most works of interactive fiction contain occasional vignettes, either in terms of short scenes of narrative, or in the behaviour of particular things or rooms, which we would like to test without the fuss of using the full game-level Skein tool. The examples in the documentation are like this: in almost every example, typing TEST ME puts the game through its paces. (Testing command) Solutions or sequences for testing ("scripts") can be defined with sentences like so: Test balloon with "get balloon / blow balloon / drop balloon". This has no effect on the design itself, but ensures that when the game is played, typing "test balloon" will run through the given three commands in sequence, as if we had typed "get balloon" and then "blow balloon" and then "drop balloon". The name for the test (balloon in this example) has to be a single word. Typing just "test" at the game prompt gives a list of all the test scripts known to the game. Test scripts can make use of each other, for instance: Test all with "test balloon / test door". One convenient way to keep track of the solution for a work being written is to include a test script at the end of each section, and to place a master test script (like "test all") at the top of the source. But different designers will prefer different approaches, and this testing system is no more than an optional convenience. Many tests will only be sensible in given places, which may be hard to reach from the initial position; or with the aid of given things, which may be difficult to obtain. We are therefore allowed to add stipulations to test scripts: Test balloon with "get balloon / blow balloon / drop balloon" holding the balloon. The "... holding the balloon" means that the balloon will be transferred to the player's ownership immediately before the test script is run, unless it is already held. Similarly: Test jam with "get jam / taste jam / eat jam" in the Kitchen. Or we might want to say both: Test jam with "get jam / taste jam / eat jam" in the Kitchen holding the jam. (Single quotation marks in test scripts are interpreted the same way in test scripts as they are in other text: that is, they are sometimes read as double-quotes unless they appear to be present as apostrophes. The notation ['] forces a single quotation mark if necessary. Similarly, [/] forces a literal forward slash, and prevents the / from being read as dividing up two commands.) 2.9. Material not for release Special testing commands, like "TEST" and "SHOWME", are automatically excluded from the game if it is exported from the Inform application using the Release button. We sometimes want to write our own for-testing-purposes-only code, though, and for this purpose we are allowed to designate whole headings as being "not for release": Section 10 - Open sesame - Not for release Universal opening is an action applying to nothing. Understand "open sesame" as universal opening. Carry out universal opening: now all doors are open. Report universal opening: say "Open Sesame!" Clearly we do not wish the final reader to be able to type "OPEN SESAME", so this whole heading will be disregarded in the Release version, as will any heading whose name includes "not for release". Note that if a chapter, say, is marked as "not for release", then its subheadings (mere sections) will also not be for release. If in doubt, check the "Contents" index: if any section is "not for release" then so are all of its subheadings. 2.10. Installing extensions The original Inform of 1993 provided no special facilities for "extensions" - in effect, additional packets of rules providing extra features - but the creation and circulation of these extensions soon became a flourishing part of Inform culture. Today's Inform actively promotes sharing of such extensions, both to bring writers together and to support good practice. For the user of an extension, the advantage is clear: why go to great trouble to (say) work out how to make doors open automatically as needed, when somebody else has already perfected this? For the writer of an extension, there is the satisfaction of producing a good solution to a ticklish problem, and contributing to the public good. Newcomers will probably not need extensions for quite some while, but there is nothing difficult about using them, so a few brief notes are worth giving here. (The final chapter of the documentation covers the writing of new extensions.) Extensions are identified by name (say "Following People") and also by author (say "Mary Brown"). They will probably be downloaded from the Internet as needed, or exchanged by email, but they need to be installed before they can be used. (Mac OS X only) When using Inform on Mac OS X, this means storing them in the folder (Mac OS X only) ~/Library/Inform/Extensions/ (Mac OS X only) where "~" signifies your home folder. (Your home folder and its Library subfolder will already exist, but you may need to create "Inform" and then "Extensions" by hand with the Finder.) Each author has a subfolder of this folder, and his or her extensions live inside it. Our example extension should therefore be placed as: (Mac OS X only) ~/Library/Inform/Extensions/Mary Brown/Following People (Windows only) When using Inform on Windows, this means storing them in the folder (Windows only) My Documents\Inform\Extensions (Windows only) Each author has a subfolder of this folder, and his or her extensions live inside it. Our example extension should therefore be placed as: (Windows only) My Documents\Inform\Extensions\Mary Brown\Following People (Linux only) When using Inform on Linux, this means storing them in the folder (Linux only) ~/Inform/Extensions/ (Linux only) where "~" signifies your home folder. (This will have been created for you the first time you ran i7.) Each author has a subfolder of this folder, and his or her extensions live inside it. Our example extension should therefore be placed as: (Linux only) ~/Inform/Extensions/Mary Brown/Following People (Gnome only) When using Inform on Linux, this means storing them in the folder (Gnome only) ~/Inform/Extensions/ (Gnome only) where "~" signifies your home folder. (This will have been created for you the first time you ran i7.) Each author has a subfolder of this folder, and his or her extensions live inside it. Our example extension should therefore be placed as: (Gnome only) ~/Inform/Extensions/Mary Brown/Following People (no filename extension is used). In fact, though, Inform can automatically install extensions for us: we need only select the "Install Extension..." item on the File menu. The actual extension file is sometimes named with a ".i7x" suffix, meaning "I7 extension" - for instance, "Following People.i7x" - but this is not compulsory. To provide an example, Emily Short's useful extension "Locksmith" is one of a small number of extensions which come ready-installed as part of the basic Inform package, and need not be downloaded and installed. Each time that Inform translates any source text, it performs a quick check of the extensions available, and updates its own internal records. A directory of the extensions currently installed can be found by clicking on "Installed Extensions" from the contents page of the documentation. 2.11. Including extensions We talk about "including" such an extension into a work of IF because the process merges rules and behaviours from the extension with those we have described ourselves. It's not uncommon for contributions by five or six different people to be pooled together this way. Including an extension is only a matter of writing a single sentence in the source. For instance: Include Locksmith by Emily Short. Note that it is compulsory to name both extension and author. An extension which Inform has noticed in the extensions folder receives only a brief listing in the Inform documentation at first. But once it has been used for the first time, by being included in a successfully translated source text - even if only a tiny one - the new extension is indexed more thoroughly, and its own documentation is added to Inform's, as if extra pages were being added at the back of a ring-binder. Again, follow the "Installed Extensions" link to see this additional documentation. 2.12. Use options One more preliminary. Inform has a small number of optional settings which affect the result of translating the source. The sentence: Use American dialect. makes the resulting work of IF use American spellings (except where the designer spells otherwise) and the American convention for spelling out numbers (thus, "one hundred seventeen" not "one hundred and seventeen"). Similarly: Use the serial comma. uses a comma when printing lists: thus "Julian, Dick, George, and Anne" rather than "Julian, Dick, George and Anne". A more profound change is made by Use no scoring. which abolishes the concept of a numerical score - something which modern authors of interactive fiction often feel is inappropriate, but which Inform does provide by default. Two alternative options: Use full-length room descriptions. Use abbreviated room descriptions. change the normal way room descriptions are shown: normally they are given in full when the room is first entered, but are subsequently shortened unless the player actually asks to "look". In full-length mode, they are always given in full; in abbreviated mode, never. (The latter is a bad idea in any publically released game, but is provided for completeness and in case it may help testing.) Alternatively, we can set the traditional Infocom-style of room description to any of VERBOSE, BRIEF and SUPERBRIEF: Use VERBOSE room descriptions. Use BRIEF room descriptions. Use SUPERBRIEF room descriptions. The default is now VERBOSE, but until 2010 it was BRIEF. Next we have: Use undo prevention. which disables the UNDO verb, both in play and after death, for the benefit of games which are heavily randomised and where we do not want players to keep on UNDOing until they get a random outcome which is to their taste. (Many players consider UNDO to be their birthright, and that any work using this option is an abomination: indeed, it has even been suggested that this section of the Inform documentation be censored. To use the option is to court controversy if not outright hostility.) We can combine any number of options in a single "Use" sentence, so for example: Use American dialect and the serial comma. brings about both of these changes. 2.13. Administering classroom use Inform is increasingly used in education, where teachers sometimes need to install it on a whole room of computers at once, and want to monitor their students' progress. There is no special "classroom" version of Inform, but a couple of small administration features in the standard Inform - usually never needed - might be helpful to teachers. When Inform starts up, it now looks for a file called Options.txt inside the user's home folder for Inform. (On Mac OS X, this is "~/Library/Inform"; on Windows, "My Documents\Inform", and so on.) If the file is present, then the text in it is added to the source text of everything Inform translates. This must be used only to set use options, specify test commands, and give release instructions. For example, the following is a valid "Options.txt": Use American dialect. Test fish with "fish/fish with pole/angle". Release along with source text. The idea is that this file can be used for setting up a standard configuration on multiple machines in a classroom setting. Here the instructor can make sure the Release button will do what she would like, and can arrange for each student's copy of Inform to respond to given Test commands: for instance, if the class has an assignment to create a simulation of a camera, the instructor could set up "Options.txt" so that TEST CAMERA would run through some commands the camera ought to respond to. A new use option, "Use telemetry recordings.", causes Inform to copy its outcome and problem messages to files in its home folder (see above) as they occur. These files are dated, so that for instance Telemetry 2009-03-25.txt contains all of the recorded activity on 25 March 2009. Telemetry only records the contents of the "Problems" panel - notes of success or failure, and problem messages - and nothing is transmitted via any network, so it isn't really surveillance. The user can deliberately add a note to the current telemetry file by writing something like this in source text: * "I don't get it! What's a kind? Why can't the lamp be lighted?" (This is a way to make a note for the benefit of someone who will read the telemetry file - for instance, to comment on a problem message that has just appeared. Note the double-quotes. Otherwise, it's meant to look like the standard way that beta-testers mark up IF transcripts.) These two features have been added in response to requests from education users. Let's suppose that Mr Lebling, who teaches 5th grade in Minnesota, wants to set things up just right for his class. He installs Inform on the ten computers they will use, and also copies an Options.txt file from his memory stick onto each one. The Options.txt file reads: Use serial comma. Use American dialect. Use telemetry recordings. Now Mr Lebling's class won't be confronted with English spellings, and so on. And most of the kids are happy, but Mr Lebling gets the feeling that young Marc wasn't really paying attention, so after class he checks that day's Telemetry file for that computer to see what Marc was up to, and whether he was stuck on something. 2.14. Limits and the Settings panel No computer has unlimited capacity, and a large, complex project may eventually bump its head against the ceiling. Inform is a system for translating textual descriptions of interactive fiction into "story files". No single format of story file is standard to the IF community. The formats developed over the history of IF differ in three key respects: - the range of computers or devices capable of playing them; - how large they are, that is, how much play they can express; - what extra-textual effects they can bring off. Inform can write to four different formats. None of these are proprietary, and none were created by the authors of Inform: each of the formats is a community property, defined by published standards documents. Each individual Inform project has its own choice of story file format, which can be changed using that project's Settings panel. The format normally used is known as version 5 of the Z-machine, or "z5", which is highly standardised and can be played on a very wide range of computers, including a few handheld devices. For a small or medium-sized work of IF with no need of pictures, its widespread playability almost certainly makes it the best choice. Larger works will need version 8, or "z8". For very large works of textual IF, or to introduce pictures, the best option is to switch to the Glulx format. (In principle, the Z-machine version 6, or "z6", is also capable of displaying pictures, but Inform's support for z6 is limited and Glulx is a much better option.) Internally, the Inform application uses a tool called Inform 6 (which was once the entire Inform system) to manufacture the story file. There are therefore two ways that large projects can run out of space: (a) By exceeding some maximum in Inform 6, or (b) By exceeding some fundamental limitation of the current story file format. In both cases, the Inform application will display a Problems page explaining that the Inform 6 tool has failed to work as intended, and refer us to the "console output" - the text produced by Inform 6 - which is normally ignored, but can be found on the Progress tab of the Errors panel. In case (a), Inform 6 will say that a memory setting has been exceeded: it will say what this setting is called (for instance "MAX_ZCODE_SIZE") and what its current value is (for instance 50000). We can then avoid the problem by adding the following use option into the source text: Use MAX_ZCODE_SIZE of 60000. And similarly for every other Inform 6 memory setting. (If the source tries to specify the same setting more than once - which is quite possible if extensions are included, with rival ideas - then the highest value is used.) In case (b), we must either switch to a larger story file format, or economise. The simplest thing to do is to switch up from z5 to z8, and then from z8 to Glulx, until no limits are reported any more. (Glulx has a huge capacity, so we need never worry about size limits again.) However, if we really do need to stick to a specific format - say, if we want a story file playable on a tiny handheld computer unable to manage Glulx - we still have a few options. Unless the story is very large (in which case there is little we can do), the "z8" format is most likely to be exhausted for lack of what is called "readable memory", with a message like so: This program has overflowed the maximum readable-memory size of the Z-machine format. See the memory map below: the start of the area marked "above readable memory" must be brought down to $10000 or less. followed by a tabulation of how the Z-machine's storage has been used, a large but not very useful diagram. The first time one runs into the problem on a large project, it can be postponed, by adding the following to the source: Use memory economy. (Economy cuts down the verbosity of some of the testing commands, but otherwise subtracts no performance.) Writing this into the source is the equivalent of a diver switching to an emergency oxygen tank: it gives us a generous safety margin, but also tells us that now is the time to wrap things up. If we hit the problem again, genuine cuts must be made. As a general rule, the most memory-expensive ingredients of an Inform design are various-to-various relations between large kinds such as "thing" or, if there are many rooms, "room". Other than that, if a kind has been festooned with new properties and we have created dozens of items of that kind, then we can get a fairly large saving simply by doing without one of those properties; and so on. The ultimate memory-saving device, of course, is the one used by book publishers when there are too many pages to bind: to cut the design into two stories, Part I and Part II. 2.15. What to do about a bug In its present guise, Inform is a young piece of software, and bugs are to be expected from time to time. The most obvious bugs are the ones which Inform catches itself, when it confesses that it has halted in failure, or translated the source text into a program which cannot be compiled further. But sometimes it will also happen that Inform will issue a misleading Problem message, or appear to work normally but to produce a game which does not do what it should have done. It is very helpful for users to report faults, so that the program can be improved for everyone else. To report a fault, please first check with the Inform home page to make sure that the version of Inform you have used to detect the fault is the latest version available. You can find the latest versions at http://inform7.com/download/ If the bug is still present in the latest version, please report the bug using Inform's bug tracking database, found at http://inform7.com/mantis/ We can search existing bug reports using the search box at http://inform7.com/mantis/view_all_bug_page.php It may be that someone else has already identified the bug and even that a workaround for users is suggested. If not, please make an account at with the bug tracking system and submit the requested information to help Inform's maintainers track and fix the fault. 2.16. Does Inform really understand English? No. No computer does, and Inform does not even try to read the whole wide range of text: it is a practical tool for a particular purpose, and it deals only with certain forms of sentence useful to that purpose. Inform source text may look like "natural language", the language we find natural among ourselves, but in the end it is a computer programming language. Many things which seem reasonable to the human reader are not understood by Inform. For instance, Inform understands something which is carried by the player but not (at present, anyway) something which the player carries even though both are perfectly good English. So it is not always safe to assume that Inform will understand any reasonable instruction it is given: when in doubt, we must go back to the manual. More philosophically, to "understand" involves contextual knowledge. Just because Inform recognises and acts on a sentence, does it really understand what we meant? It will turn out that Inform is both good and bad at this. For instance, from Mr Darcy wears a top hat. Inform will correctly deduce that Darcy is a person, because inanimate objects do not ordinarily wear clothes, and that the top hat is clothing. But it will not automatically know that Darcy is a man rather than a woman because it does not know the social convention implied by "Mr". Moreover, if instead we had written Mr Darcy carries a top hat. then Inform would not guess that the top hat is clothing. This is because it does not have the vast vocabulary and experience of a human reader: it is probably discovering the word "hat" for the first time. Finally, it is best to avoid ambiguities rather than rely on Inform to know which meaning is patently absurd. For instance, in Heatwave bone breaks clog hospital. (a headline once printed by the Oxford Mail newspaper) a human reader quickly realises that there is no clog hospital being broken. But if Inform had been taught the verbs to break and to clog then that is exactly the conclusion it would have drawn. Or an example which genuinely arose in beta-testing: The life support unit fits the egg. in which Inform construed the verb as support and not fits, and then created items called "the life" (plural) and "unit fits the egg". That disclaimer completes the groundwork, and we are ready to begin on simulating a world to explore. 2.17. Review of Chapter 2: The Source Text 1. The content of the text. (a) Assertions. An assertion is a sentence describing the initial state of the world. These are all assertions: The Twinkie is a thing. The description of the Twinkie is "A confection made of gelatin and preservatives." Two hands are part of every person. The prevailing wind is a direction that varies. Assertions are the main subject of the next two chapters. (b) Rules. Rules tell Inform how the interactive fiction is to behave under certain circumstances. A rule may be fairly short, as When play begins, say "Welcome aboard, Mr Bond." or may contain a longer sequence of instructions, as in Instead of attacking the donkey: remove the donkey from play; if the donkey carries something, now everything carried by the donkey is in the location; say "The donkey bolts, of course." Rules will be covered in much more detail later, but for now note the punctuation: a rule is a list of "phrases". Each phrase except the last ends with a semi-colon to show that the rule is not finished yet. We may only use "if..." (such as "if the donkey carries something...") within a rule, where Inform can be sure of exactly when the condition is to be considered. (As we shall see later, "Instead of attacking the donkey" tells Inform when the rule is applied.) So the following is not allowed: The Rain Forest is a room. If the player is in the Rain Forest, say "Rain falls steadily on your hat and rucksack." (If the idea is to apply this test all of the time, it needs to be wrapped up in a rule making this clear. "Every turn: if the player is..." would do the trick, as we shall see in the chapter on Time.) (c) Headings. Headings are typed in their own paragraphs (with a skipped line above and below) and start with one of the words Volume, Book, Part, Chapter or Section. (When typed, they immediately become bold in the source panel.) Headings are useful because they help us to organise and find our way around a large source text. They also make problem messages clearer. (d) Comments. Comments enclosed in square brackets [like this] allow us to insert our own remarks about the source text. Inform ignores them: they're for our own benefit only. (e) Tables of information. These have not yet appeared, but look like tables printed in books. They will be the subject of a later chapter. (f) A few special sentences. A few sentences are read by Inform as instructions on how we want the source text to be understood. For instance, we can say "Use American dialect" or tell Inform to "Include Locksmith by Emily Short" (or some other extension set of rules, by some other author). 2. Testing and Troubleshooting (a) What's where? Sometimes, during play, we want to see where everything now is. Inform contains a number of testing commands giving us a look behind the scenes: one of these is SHOWME. For instance, if there is a helmet somewhere, SHOWME HELMET tells us about it. Typing SHOWME alone tells us about the current location. (b) Making our own test commands. We can for instance write: Test helmet with "wear helmet / listen / x helmet / doff helmet". This creates a short sequence of commands which we can replay during the game at any time in order to test whether the helmet does what we intended. (Like all testing commands, these will be omitted from any finished games we create with the Release button. We can exclude other testing-purposes-only material, too, by placing it under a heading which includes the words "not for release".) (c) Limits. There are several formats in which we can release a finished game. The advantage of the smallest "z5" format is that it is highly portable and can be played on the widest selection of machines, including various kinds of handheld computer. Inform uses this format for any newly-begun project. If we should run out of space, Inform will advise on the options, but the only way to gain a large amount of extra room is to use the Settings panel to switch to a larger format. Chapter 3: Things 3.1. Descriptions At its simplest, the interactive fiction will be simulating a physical world to explore. The forerunner of today's IF is generally agreed to be a computer simulation by Will Crowther of the exploration of a cave system in the Mammoth and Flint Ridge chain of caves in Kentucky, a part of which might be described in Inform thus: "Cave Entrance" The Cobble Crawl is a room. "You are crawling over cobbles in a low passage. There is a dim light at the east end of the passage." A wicker cage is here. "There is a small wicker cage discarded nearby." The Debris Room is west of the Crawl. "You are in a debris room filled with stuff washed in from the surface. A low wide passage with cobbles becomes plugged with mud and debris here, but an awkward canyon leads upward and west. A note on the wall says, 'Magic word XYZZY'." The black rod is here. "A three foot black rod with a rusty star on one end lies nearby." Above the Debris Room is the Sloping E/W Canyon. West of the Canyon is the Orange River Chamber. Here we sketch in four of Crowther's locations, and two objects: just enough to be able to walk around the caves and pick up the rod and the cage. The text in quotation marks will appear verbatim as paragraphs shown to the player as the caves are explored. The first paragraph, as we have seen, is the title of the work. The other quotations describe the places and objects introduced. If we play this game, we find that we can type TAKE CAGE or TAKE WICKER CAGE, for instance, but not TAKE SMALL CAGE. Inform saw that we called this "a wicker cage" when it first appeared in the source text, and assumed that the player would call it that, too. (Whereas it didn't look inside the descriptive text to allow for TAKE SMALL CAGE or TAKE DISCARDED CAGE or TAKE NEARBY CAGE.) A small limitation here is that probably only the first 9 letters of each word are read from the player's command. This is plenty for handling the wicker cage and the black rod, but it might be embarrassing at a meeting of the Justice League to find that KISS SUPERHERO and KISS SUPERHEROINE read as if they are the same command. So we have already found that Inform has made some assumptions about what we want, and imposed some limitations on how much computational effort to go to when the work of IF is finally played. If Inform guesses what we need wrongly, we need to know more advanced features of the language in order to overcome these problems. (We shall see how to change the way the player's commands are read in the chapter on Understanding.) This is often how Inform works: make the standard way of doing things as simple as possible to describe, but allow almost any behaviour to be altered by more elaborate source text. Example 2 (*): Verbosity 1 Making rooms give full descriptions each time we enter, even if we have visited before. Example 3 (**): Slightly Wrong A room whose description changes slightly after our first visit there. 3.2. Rooms and the map Rooms are joined together at their edges by "map connections", most of which are pathways in one of the eight cardinal compass directions: north, northeast (written without a hyphen), east, southeast, south, southwest, west, northwest. We also have up and down, suitable for staircases or ladders. In real life, people are seldom conscious of their compass bearing when walking around buildings, but it makes a concise and unconfusing way for the player to say where to go next, so is generally accepted as a convention of the genre. Two more directions are provided by Inform: "inside" and "outside". These are best used when one location is, say, a meadow and the other is a woodcutter's hut in the middle of it; we might then say Inside from the Meadow is the woodcutter's hut. The "from" is important, as it clarifies that we intend to link two different locations, not to create an item - the hut - in a single location - the meadow. A problem which sometimes arises when laying out maps is that Inform allows short forms of room names to be used as abbreviations. This is usually a good idea, but has unfortunate results if we write: The Airport Road is west of the Fish Packing Plant. The Airport is west of the Airport Road. ...because "Airport" is taken as a reference to "Airport Road", so Inform makes only two locations, one of which supernaturally leads to itself. We can avoid this by writing: The Airport Road is west of the Fish Packing Plant. A room called the Airport is west of the Airport Road. Using "called" is often a good way to specify something whose name might give rise to confusion otherwise. It always makes something new, and it is also neatly concise, because we can establish something's kind and name in the same sentence. As another example, suppose we want to create a room called "South of the Hut", to south of the Hut. We can't do so like this: South of the Hut is a room. South of the Hut is south of the Hut. ...because Inform will read that first sentence as placing a (nameless) room to the south of a room called "Hut". Once again "called" can save the day: South of the Hut is a room called South of the Hut. It is best to use "called" in the simplest way possible, and in particular, best not to use "called" twice in the same sentence. Consider: The kitchen cabinet contains a container called a mixing bowl and a portable supporter called a platter. It is unlikely that anyone would want to name something "a mixing bowl and a portable supporter called a platter", but not impossible, and Inform tends not to be a good judge of what is likely. Example 4 (*): Port Royal 1 A partial implementation of Port Royal, Jamaica, set before the earthquake of 1692 demolished large portions of the city. Example 5 (**): Up and Up Adding a short message as the player approaches a room, before the room description itself appears. Example 6 (***): Starry Void Creating a booth that can be seen from the outside, opened and closed, and entered as a separate room. 3.3. One-way connections Connections are ordinarily two-way, but do not have to be. One of the map connections in the Mammoth Cave simulation was made by the sentence: The Debris Room is west of the Crawl. Besides reading this sentence at face value, Inform also deduced that the Crawl was probably meant to be east of the Debris Room: in other words, that the path between them is a two-way one. When Inform makes guesses like this, it treats them as being less certain than anything explicitly stated in the source. Inform will quietly overturn its assumption if information comes to hand which shows that it was wrong. That might happen in this case if another sentence read: The Hidden Alcove is east of the Debris Room. These two sentences are not contradictory: Inform allows them both, simply accepting that the world is more complicated than it first assumed. There are relatively few situations where Inform has to make educated guesses, but when it does, it tries always to follow Occam's Razor by constructing the simplest model world consistent with the information in the Source text. We can even explicitly make a route which turns around as it leads between two rooms: West of the Garden is south of the Meadow. Finally, if we want to establish a route which cannot be retraced at all, we can specify that a particular direction leads nowhere: East of the Debris Room is nowhere. Example 7 (*): Port Royal 2 Another part of Port Royal, with less typical map connections. Example 8 (*): The Unbuttoned Elevator Affair A simple elevator connecting two floors which is operated simply by walking in and out, and has no buttons or fancy doors. 3.4. Regions and the index map Rooms represent individual places to which one can go, but we tend to think of the world around us in larger pieces: we think of a house and a garden, rather than each of the single rooms of the house and all corners of its garden. To Inform a collection of rooms is called a "region", and we can create one like so: The Arboretum is east of the Botanical Gardens. Northwest of the Gardens is the Tropical Greenhouse. The Public Area is a region. The Arboretum and Gardens are in the Public Area. The real usefulness of creating regions like "Public Area" will only appear later, when we begin defining rules of play which apply in some areas but not others, but in the mean time we can see the effect by turning to the World tab of the Index. In the World Index, Inform draws a map - or at least a stylised attempt at a diagram of the rooms and their connections: this will not always correspond to how we imagine things, but with any luck it should mostly be right. Rooms are represented by coloured squares, and the colour-coding is done by region. In the above example, the two "Public Area" rooms are coloured green (as it happens); the Greenhouse, since it belongs to no region, is a neutral grey. Regions can be put inside each other: The University Parks is a region. The Public Area is in the University Parks. but they are not allowed to overlap other than by one being entirely inside the other. (See Improving the index map for ways to adjust the way the index map is drawn or exported for publication.) Example 9 (*): Port Royal 3 Division of Port Royal into regions. 3.5. Kinds The following description runs to only 33 words, but makes a surprisingly intricate design. It not only places things within rooms, but also places them very specifically with respect to each other: "Midsummer Day" East of the Garden is the Gazebo. Above is the Treehouse. A billiards table is in the Gazebo. On it is a trophy cup. A starting pistol is in the cup. Inform needs to identify the places and objects being described by the nouns here, and to guess what it can about them. For instance, the pistol can be picked up but not walked inside, whereas the Treehouse is the reverse. (This is obvious to someone who knows what these words mean, less obvious to a computer which does not, but the text contains sufficient clues.) Inform does this by sorting the various nouns into different categories, which are called "kinds". For instance: Garden, Gazebo, Treehouse - room billiards table - supporter cup - container starting pistol - thing East, up (implied by "above") - direction (A container is something which can contain other things, and a supporter similarly.) For instance Inform knows that if one thing is in another, then the second thing is either a room or a container, and if one thing is on another, the second thing is a supporter. This worked nicely for the design above, but: In the Treehouse is a cardboard box. results in the cardboard box being made only a "thing": because nothing has been put inside it, there is no reason for Inform - which does not know what a cardboard box looks like - to guess that it is a "container". So we need to add: The box is a container. It is rather clumsy to have to write two sentences like this, so we would normally write this instead: In the Treehouse is a container called the cardboard box. Example 10 (*): First Name Basis Allowing the player to use different synonyms to refer to something. Example 11 (*): Midsummer Day A few sentences laying out a garden together with some things which might be found in it. 3.6. Either/or properties Some containers, like bottles, can be opened: others, like buckets, cannot. If they can be opened, then sometimes they will be open, and sometimes closed. These are examples of properties, which can change during play. The following source sets some properties: The cardboard box is a closed container. The glass bottle is a transparent open container. The box is fixed in place and openable. There are only four different properties referred to here. Closed means not open, and vice versa, so these two adjectives both refer to the same property. (As might be expected, when a container is open, one can see inside and place things within, or take them out.) The glass bottle and the box being containers is a matter of their kinds, which is something fundamental and immutable, so "container" does not count as a property. A "transparent" container is one which we can see inside even when it is closed, and the opposite is an "opaque" container. The property of being "fixed in place" ensures that the player cannot pick the item up and walk away with it: this is useful for such things as oak trees or heavy furniture. The opposite condition is to be "portable". A container which is "openable" can be opened or closed by the player. This property has no friendly adjective for its opposite, so we would need to write "not openable". (Inform does not guess that, say, "unopenable" means "not openable". Such guesses are too risky, when so many "un-" words are irregular: "unified", "uncle", "ungulate" and so on.) With a really large cardboard box, we might imagine that the player could get inside: such a container should be declared "enterable". Example 12 (*): Tamed Examples of a container and a supporter that can be entered, as well as nested rooms. 3.7. Properties depend on kind Properties depend very much on kind. It makes no sense to ask whether a room is transparent or opaque, for instance, so Inform will not allow this either to be specified or queried. Another way that kind influences properties can be seen from an earlier example: The Gazebo is a room. A billiards table is in the Gazebo. On it is a trophy cup. A starting pistol is in the cup. The cup, the pistol and the table are all allowed to have the "fixed in place" property, but in fact only the table actually has it: the cup and the pistol are created as "portable" instead. This is because Inform knows that most things are portable, but that supporters - such as the table - are usually fixed in place. If this assumption is wrong, we need only add the line: The table is portable. Example 13 (*): Disenchantment Bay 1 A running example in this chapter, Disenchantment Bay, involves chartering a boat. This is the first step: creating the cabin. 3.8. Scenery As we have just seen, making something "fixed in place" will prevent it from being picked up or moved. But it remains substantial enough to be described in its own paragraph of text when the player visits its location. This can be unfortunate if it has also been described already in the body of the main description for that location. For instance, if we wrote: The Orchard is a room. "Within this quadrille of pear trees, a single gnarled old oak remains as a memory of centuries past." The gnarled old oak tree is fixed in place in the Orchard. This would end up describing the oak twice, once in the paragraph about the Orchard, then again in a list of things within it: Orchard Within this quadrille of pear trees, a single gnarled old oak remains as a memory of centuries past. You can see a gnarled old oak tree here. We avoid this by making it "scenery" instead of "fixed in place": The gnarled old oak tree is scenery in the Orchard. Any thing can be scenery, and this does not bar it from playing a part in the game: it simply means that it will be immobile and that it will not be described independently of its room. Being immobile, scenery should not be used for portable objects that are meant to be left out of the room description. If a supporter is scenery, it may still be mentioned in the room description after all, but only as part of a paragraph about other items, such as On the teak table are a candlestick and a copy of the Financial Times. If the player takes the candlestick and the Times, the teak table will disappear from mention. (Scenery containers do not behave in this way: their contents are assumed to be less immediately visible, and will be mentioned only if the player looks inside them.) Example 14 (*): Replanting Changing the response when the player tries to take something that is scenery. Example 15 (*): Disenchantment Bay 2 Disenchantment Bay: creating some of the objects in the cabin's description. 3.9. Backdrops It is a cardinal rule that nothing can be in more than one place at the same time, but rules were made to be broken, and an exception is allowed for a special kind of thing called a "backdrop". For instance: "Streaming" The Upper Cave is above the Rock Pool. The stream is a backdrop. It is in the Upper Cave and the Rock Pool. Backdrops are ordinarily in the background: if the sky needed to be referred to in the course of play, it might be represented by a backdrop, for instance. Here we have a stream of water running through two rooms, though it might be any number. Backdrops are always fixed in place. Backdrops can be put in regions as well as rooms, and if so, then they are present at every room in the given region (or regions), as well as any specific rooms they may also be put into. For instance: The Outdoors Area is a region. The Moon is a backdrop. The Moon is in the Outdoors Area. The Moon is in the Skylight Room. The special place "everywhere" can be given as the location of a backdrop to make it omnipresent: The sky is a backdrop. The sky is everywhere. Inform assumes that backdrops are also scenery unless told otherwise, so this will not result in messages like "You can also see the sky here." being included in room descriptions. In the case of the stream above, we could artfully mention it in passing in the room descriptions of the Upper Cave and the Rock Pool. (-See Moving backdrops for ways to place backdrops in dynamically changing selections of rooms.) Example 16 (*): Disenchantment Bay 3 Disenchantment Bay: adding a view of the glacier. 3.10. Properties holding text The properties we have seen so far have all been either/or: either open or closed, either transparent or opaque, either fixed in place or portable, either openable or not openable. However, some properties can have a much wider range of possibilities. For instance, the "description" of a room is the text revealed when the player first enters it, or types "look". This needs to be textual: Inform would complain if, for instance, we tried to set the description of something to the number 42. We have already seen a concise way to set the description of a room: The Painted Room is north of the Undertomb. "This is the Painted Room, where strange wall drawings leap out of the dark at the gleam of your candle: men with long wings and great eyes, serene and morose." This does the same thing as: The Painted Room is north of the Undertomb. The description of the Painted Room is "This is the Painted Room, where strange wall drawings leap out of the dark at the gleam of your candle: men with long wings and great eyes, serene and morose." Or even: The Painted Room is north of the Undertomb. The description is "This is the Painted Room, where strange wall drawings leap out of the dark at the gleam of your candle: men with long wings and great eyes, serene and morose." 3.11. Two descriptions of things The player's first sight of something is the text used as its "initial appearance": The plain ring is here. "Cast aside, as if worthless, is a plain brass ring." This text appears as a separate paragraph in the text describing the Painted Room. It will continue to be used until the first time player picks the ring up (if this ever happens), so it normally describes things in their original, undisturbed context. (Inform uses an either/or property called "handled" for this: something is "handled" if it has at some point been held by the player.) Thus when a piece of text stands alone as a sentence in its own right, then this is either the "description" of the most recently discussed room, or the "initial appearance" of the most recently discussed thing. Either way, it is used verbatim as a paragraph in the text shown to the player visiting the room in question. But a thing also has an ordinary "description", which is used to give a close-up look at it. This text is ordinarily only revealed to the player when a command like "examine ring" is keyed in: The description of the plain ring is "No better than the loops of metal the old women use for fastening curtains." (-See Creating a scene for the description of a scene, which is set in the same way.) Example 17 (*): Disenchantment Bay 4 Disenchantment Bay: fleshing out the descriptions of things on the boat. Example 18 (**): Laura Some general advice about creating objects with unusual or awkward names, and a discussion of the use of printed names. 3.12. Doors The map of an interactive fiction is the layout of rooms and the entrances and exits which connect them. So far, these map connections have always run from one room to another, like so: The Painted Room is north of the Undertomb. However, we can also interpose doors between rooms, like so: The heavy iron grating is east of the Orchard and west of the Undertomb. The grating is a door. The second sentence is needed since otherwise Inform will take "heavy iron grating" to be the name of a third room, whereas what we want is for the grating to be something physically present in both the Orchard and in the Undertomb, and acting as a conduit between them. To this end it needs to be a "door", a kind we have not so far seen. In the absence of any other instruction, a newly created door will be fixed in place, closed and openable. The grating really does come in between the two rooms: the grating is what lies immediately east of the Orchard, not the Undertomb room. So if we wrote the following: The Undertomb is east of the Orchard. The heavy iron grating is east of the Orchard and west of the Undertomb. The grating is a door. then Inform would say that this is a contradiction: we said the Undertomb was east of the Orchard, but then we said that the grating was east of the Orchard. Inform's "door" kind can be used for all manner of conduits, so the word door need not be taken literally. In Ursula K. LeGuin's beguiling novel "The Tombs of Atuan", from which the above rooms are stolen, it is not a grating which interposes, but: The red rock stair is east of the Orchard and above the Undertomb. The stair is an open door. The stair is not openable. In real life, most doors are two-sided, and can be used from either of the rooms which they join, but this is not always convenient for interactive fiction. Here is a one-sided door: The blue door is a door. It is south of Notting Hill. Through it is the Flat Landing. (Note the use of "it" here as an optional abbreviation.) This will make a door visible only on the Notting Hill side; no map connection will be made in the reverse direction, unless we ask for one. So much for creating and describing individual doors. Once we need to write about doors in general, we are likely to want a way to find out where a given door sits in the map. The following phrases reveal this:

front side of (object) ... room
This phrase produces the first of the one or two rooms containing a door - first in the order given in the source text. Example: if The red rock stair is east of the Orchard and above the Undertomb. then "front side of the red rock stair" produces the Orchard. For a one-sided door, this produces the only room containing the door.

back side of (object) ... room
This phrase produces the last of the one or two rooms containing a door - last in the order given in the source text. Example: if The red rock stair is east of the Orchard and above the Undertomb. then "back side of the red rock stair" produces the Undertomb. A one-sided door has no "back side."
More often, we are dealing with a door and want to know what it leads to, but that depends where we're standing:

other side of (door) from (room) ... object
This phrase produces the room on the other side of the door, as seen from the given vantage point, which needs to be one of its sides. Example: if The red rock stair is east of the Orchard and above the Undertomb. then "other side of the red rock stair from the Undertomb" produces the Orchard, and vice versa.

direction of (door) from (room) ... object
This phrase produces the direction in which the door leads, as seen from the given vantage point, which needs to be one of its sides. Example: if The red rock stair is east of the Orchard and above the Undertomb. then "direction of the red rock stair from the Undertomb" produces up.
(-See Adjacent rooms and routes through the map for more phrases which can look at the current map layout.) Example 19 (*): Disenchantment Bay 5 Disenchantment Bay: adding the door and the deck to our charter boat. Example 20 (**): Escape Window that can be climbed through or looked through. Example 21 (***): Garibaldi 1 Providing a security readout device by which the player can check on the status of all doors in the game. 3.13. Locks and keys It seems unwise for a door in Notting Hill to be unlocked, so: The blue door is lockable and locked. The matching key of the blue door is the brass Yale key. Since the second sentence here is a little clumsy, we can equivalently say The brass Yale key unlocks the blue door. Yet a third way to say this is: The blue door has matching key the brass Yale key. This introduces three new properties: a door can be locked or unlocked; lockable or not lockable; and it can have a matching key, which must be another thing. The same thing can be the matching key of many different locks: and note that a door can be locked and even lockable without having a matching key at all, in which case the player trying to open it will be permanently out of luck. Doors are ordinarily unlocked, not lockable, and without a matching key. Containers can also have locks, in exactly the same way, and are allowed to have the same properties. On the other hand supporters never have locks: it makes no sense to be able to lock a tabletop, for instance, and Inform will not allow any discussion of the matching key of a supporter, or of a supporter being locked or unlocked. Example 22 (*): Disenchantment Bay 6 Disenchantment Bay: locking up the charter boat's fishing rods. Example 23 (**): Neighborhood Watch A locked door that can be locked or unlocked without a key from one side, but not from the other. 3.14. Devices and descriptions A "device" is another of the standard kinds of thing, and should be used for anything which can be switched on or off: a light switch, say, or a slide projector. Devices are generally machines, clockwork or electrical. A device is always either "switched on" or "switched off", but is switched off unless we specify otherwise. That makes three kinds of thing which will likely change their appearance according to which of their two possible states they are in: doors and containers, which can be open or closed; and devices, which can be switched on or switched off. We would like to produce text accordingly, and we can do this using Inform's ability to make (almost) any piece of text change with circumstances. For instance: The coffin is an openable container in the Undertomb. "[if open]The lid of a plank coffin yawns open.[otherwise]A plank coffin lies upon the dirt floor of the Tomb." We could use a similar trick to make the appearance of a device change "if switched on". There will be much more about text substitutions, as instructions in square brackets like these are called, in later chapters. (See Text with substitutions for more on varying what is printed.) Example 24 (*): Disenchantment Bay 7 Disenchantment Bay: making the radar and instruments switch on and off. Example 25 (**): Down Below A light switch which makes the room it is in dark or light. 3.15. Light and darkness Rooms can be "dark" or "lighted", though they are lighted by default, and are lighted in all the examples we have seen so far. The Sinister Cave is a dark room. "A profoundly disquieting rock formation, apparently sculptured by some demonic hand, this is not a cave in which to relax." When the player is in a dark room, he can still go in various directions, but he cannot see the room description or interact with any of the objects in the room, except those he is holding. This means that, unless we should change the Cave in some way during play, the text above ("A profoundly...") will only be read if the player succeeds in bringing light into the Cave, perhaps by bringing along the following: The flaming torch is in the Sandy Passage. "Stuck loosely into the sand is a flaming torch." The flaming torch is lit. A thing with the property of being "lit" will enable the player to see inside dark rooms, and to carry out other activities requiring light, such as examining items. A lit thing in an open container will still light up a room; a lit thing in a closed container will not, unless the container has been given the "transparent" property. It is possible to adjust the way darkness behaves, and we will see more on this topic in the chapter on Activities. (See Printing a refusal to act in the dark for the first of several ways to control what is printed in the dark.) 3.16. Vehicles and pushable things Next in the tour of standard kinds is the "vehicle". This behaves like (indeed, is) an enterable container, except that it will not be portable unless this is specified. In the Garage is a vehicle called the red sports car. The player can enter the sports car and then move around riding inside it, by typing directions exactly as if on foot: and the game will print names of rooms with "(in the red sports car)" appended, lest this be forgotten. We have already seen that some things are portable, others fixed in place. In fact we can also make a third sort of thing: those which, although not portable, can be pushed from one room to another with commands like "push the wheelbarrow north". At a pinch, we might just be willing to allow: The red sports car is pushable between rooms. But of course this is a property which almost any thing can have, not just a vehicle. (Only "almost" because Inform will not allow a door to be pushable between rooms, in the interests of realism rather than surrealism.) If we need vehicles which the passenger sits on top of, like a horse or a tractor, the standard "vehicle" kind will not be ideal. However, by loading one of the extensions which comes ready-installed: Include Rideable Vehicles by Graham Nelson. ...we are provided with two more kinds, "rideable vehicle" and "rideable animal", just right for the tractor and the horse respectively. (As with all extensions, the documentation can be seen by clicking Go on some source which contains the above line, and then turning to the Contents index.) (See Going by, going through, going with for further ways to customize vehicle behaviour.) Example 26 (*): Peugeot A journey from one room to another that requires the player to be on a vehicle. Example 27 (**): Disenchantment Bay 8 Disenchantment Bay: a pushable chest of ice for the boat. Example 28 (***): Hover Letting the player see a modified room description when he's viewing the place from inside a vehicle. 3.17. Men, women and animals Rounding out the standard kinds provided by Inform are four for living things: "person", which is a kind of thing, and "man", "woman" and "animal", all kinds of person. For instance: In the Ballroom is a man called Mr Darcy. For the time being, men and women will be little more than waxworks: they will come to life only when we go beyond the present stage of creating an initial state of the world. People can be male, female, or neuter: this is an attribute for the "person" kind, and it affects play at run-time a little, because the player can use "him" and "her" to refer to male or female people encountered, or "it" for neuter animals. Men and women are always male and female respectively, but the gender of an animal can be any of the three: male or female if we want (say) a stallion or a nanny goat; neuter if we want a beetle or an earthworm. The main question is whether we want to call the animal "him", "her", or "it". Animals are male unless we say otherwise: The mare is a female animal in the Stables. Example 29 (*): Disenchantment Bay 9 Disenchantment Bay: enter the charter boat's Captain. 3.18. Articles and proper names Suppose we have said that: In the Ballroom is a man called Mr Darcy. When the Ballroom is visited, the man is listed in the description of the room as "Mr Darcy", not as "a Mr Darcy". This happened not because Inform recognised that Darcy is a proper name, or even because men tend to have proper names, but because Inform noticed that we did not use "a", "an", "the" or "some" in the sentence which created him. The following shows most of the options: The Belfry is a room. A bat is in the Belfry. The bell is in the Belfry. Some woodworm are in the Belfry. A man called William Snelson is in the Belfry. A woman called the sexton's wife is in the Belfry. A man called a bellringer is in the Belfry. In the Belfry is a man called the vicar. The indefinite article of the vicar is "your local". In the resulting game, we read: You can see a bat, a bell, some woodworm, William Snelson, the sexton's wife, a bellringer and your local vicar here. The subtlest rule here is in the handling of "the". We wrote "The bell is in the Belfry", but this did not result in the bell always being called "the" bell: in fact, writing "A bell is in the Belfry" would have had the same effect. On the other hand, "A woman called the sexton's wife is in the Belfry." led to the wife always being known as "the" sexton's wife, not "a" sexton's wife, because Inform thinks the choice of article after "called" shows more of our intention than it would elsewhere. These rules will never be perfect in all situations, so we are also allowed to specify indefinite articles by hand, as the vicar's case shows. "Some" is worth a closer look, because English uses it in several different ways. By introducing the woodworm with "some", above, we established that it was plural. We might imagine that there are many worms, even though they are represented by a single thing in Inform. We can expect to see text in the story such as: You can see some woodworm here. The woodworm are fixed in place. But suppose we wanted something which there is an amount of, but which is not made up of individual items - a so-called mass noun like "water", or "bread". Now we can write: The water is here. The indefinite article is "some". and this time Inform does not treat the "some water" thing as a plural, so we might read: You can see some water here. The water is hardly portable. rather than "The water are hardly portable." Finally, we can override these settings, if they still come out not as we intend, by explicitly changing the either/or properties "singular-named" (vs "plural-named") and "proper-named" (vs "improper-named"). Example 30 (*): Belfry You can see a bat, a bell, some woodworm, William Snelson, the sexton's wife, a bellringer and your local vicar here. Example 31 (**): Gopher-wood Changing the name of a character in the middle of play, removing the article. 3.19. Carrying capacity The containers and supporters created so far have been boundlessly capacious: or rather, though we seldom notice the difference, have had a maximum carrying capacity of 100 items. This is clearly unrealistic for a small purse or a modest mantelpiece. We can impose upper limits with sentences like so: The carrying capacity of the jewelled purse is 2. The bijou mantelpiece has carrying capacity 3. Attempts by the player to overfill, or overload, will now be rebuffed with a message such as "There is no room on the mantelpiece". The player is not a container or a supporter, but nevertheless does have a carrying capacity: this is interpreted to mean the maximum number of items which can be carried at once. The carrying capacity of the player is 4. These restrictions only apply to the player (and other in-world characters): as the omnipotent creators, we are not restrained by them. Nothing prevents this: The carrying capacity of the jewelled purse is 2. The diamond, the ruby and the sapphire are in the purse. The player will be able to remove all three items, but only put two of them back. (This is probably something we only want very occasionally: perhaps to create a sack stuffed almost to bursting point.) 3.20. Possessions and clothing We have seen how to place objects in rooms, and in containers or on supporters. But what about people? Perhaps it could be said that they "contain" the fillings in their teeth, or "support" a top hat, but this is not very natural. Inform therefore never speaks of things being "in" or "on" people. Instead, they have two sorts of possessions: the things they carry, and the things they wear. (Body parts, such as arms and legs, are different again: see "parts" below for a clue to how to do these.) Thus: Mr Darcy wears a top hat. Mr Darcy carries a silver sword. In fact, Inform deduces from this not only who owns the hat and the sword, but also that Darcy has the kind "person", because only people can wear or carry. As all the assertion verbs do, "to wear" and "to carry" have participles which Inform knows about. So we could equally well write: The scarlet coat is worn by Mr Wickham. The duelling pistol is carried by Mr Wickham. If we do not specify who does the wearing, or carrying, then this is assumed to be the player. Thus: A brass lantern and a rusty iron key are carried. The mosquito-repellent hat is worn. It would make no sense to "wear" the key, for instance, so Inform needs to distinguish between what is clothing and what is not. It does this with an either/or property called "wearable": if something has this property then the player will be allowed to wear it, provided it can first be picked up. Anything which is worn by somebody at the start of play is assumed to be wearable (unless we say otherwise). But if nobody is initially wearing the item in question, then we have to be explicit: The player carries a scarlet gown. The gown is wearable. (When we come to asking questions about the current situation, we will need to remember that "to carry" and "to wear" are different. Thus "if Lancelot carries the plate armour" will not be true if he is wearing it rather than carrying it under his arm. As we will later see, we can instead vaguely say "if Lancelot has the plate armour" to mean either carrying or wearing.) (See To carry, to wear, to have for a more detailed explanation of carrying, wearing, and possessing as Inform understands them.) Example 32 (*): Disenchantment Bay 10 Disenchantment Bay: things for the player and the characters to wear and carry. 3.21. The player's holdall When the player has only limited carrying capacity, game play is likely to be tiresome, but we can make life easier by providing a way for the player to carry endless items without dozens of free hands to hold them all: "Sackcloth" The Attic is a room. The old blue rucksack is a player's holdall. The player is wearing the rucksack. The carrying capacity of the player is 3. In the Attic are a CD entitled No Smoke Without Fire, a 70s photograph of an American winning Wimbledon, a fraxinus branch, an urn holding your late great-aunt's remains, a convention badge from the American Society of Hypertension and a ghost story by M R James. This example game introduces a new kind of container, the "player's holdall". This is a kind of which most games will contain at most one example, but in principle there can be any number. A player's holdall is a capacious bag into which the player automatically places surplus items whenever his or her hands are full: trying the above example game and getting the items one by one will give the general idea. Of course, if the carrying capacity of the player is never reached then there will never be any surplus items and a player's holdall will behave just like any other (portable, usually openable) container. Example 33 (*): Disenchantment Bay 11 Disenchantment Bay: making a holdall of the backpack. 3.22. Food We have nearly reached the end of the chapter on Things, but one either/or property for things remains: every thing is either "edible" or "inedible". Unless we say otherwise, things are inedible. But for instance we might write: The player carries a Macintosh apple. The Macintosh is edible. (The type of computer is named after a variety of apple descended from a tree cultivated in 1811 by John McIntosh of Ontario.) Edible things are just like inedible ones, except that the player can EAT them. This will usually only consume the foodstuff in question, effectively destroying it, but using techniques from later chapters we could make the consequences more interesting. 3.23. Parts of things Everything has one and only one kind. This is both good and bad: good for clarity, bad if something needs to behave in two different ways at once. How might we simulate a car with an ignition key, given that no single thing can be both a "vehicle" and a "device" at the same time? The Inform world model takes the view that such a car is too complicated to be simulated with a single thing. Instead it should be simulated as a vehicle (the car) which has a device (the ignition) attached. This is done using a third kind of containment to those seen so far ("in..." and "on..."): "part of". "Buttons" The Confectionary Workshop is a room. The Chocolate Machine is here. "The Chocolate Machine has pride of place. A lever and two buttons, one white, the other brown, seem to be the only controls. On top is a hopper." A container called the hopper is part of the Chocolate Machine. The lever, the white button and the brown button are parts of the Chocolate Machine. The Chocolatier's desk is here. "The Chocolatier evidently works at the imposing green-leather topped desk facing the Machine. It has three drawers with brass handles." The upper drawer, the middle drawer and the lower drawer are parts of the desk. The upper drawer, the middle drawer and the lower drawer are openable closed containers. In the middle drawer is a sugared almond. In the lower drawer is a Battenburg cake. On the desk is a liquorice twist. The cake, the twist and the almond are edible. The machine and the desk each have several "parts" representing subsidiary pieces of themselves. The desk is a "supporter" (it needs to be, for the liquorice twist to be on top) but also has three "containers" attached, each of which can be opened or closed independently. In the interests of realism, the standard rules of play protect these composite things. Thus if the desk were to be moved elsewhere (rolling on sugar casters perhaps) then its parts would move with it, and the player is not allowed to detach parts of things: the drawers can be opened or closed, but not pulled out altogether. Note that rooms and regions are not allowed to have parts. (Rooms are already parts of regions, and to divide up rooms, we can either make several rooms or place containers or other obstacles in a single one.) Example 34 (***): Brown A red sticky label which can be attached to anything in the game, or removed again. Example 35 (****): Disenchantment Bay 12 A final trip to Disenchantment Bay: the scenario turned into a somewhat fuller scene, with various features that have not yet been explained. 3.24. Concealment Though realism can become tiresome in interactive fiction, there are times when we cannot go along with Inform's normal assumption that all of a person's possessions are visible to everybody else. People are not like containers, which either show all of their holdings or not, according to whether they are open or transparent. If a man is carrying a fishing rod and a wallet, one will be on open show, the other not. Some clothing is outwardly visible, but not all. Whether or not something is concealed is not like the either/or properties we have seen so far - such as being "open" or "closed" - because it is not really a property of the thing itself, but depends on the habitual behaviour of its current owner. To talk about behaviour we have to use sentences of a kind not seen so far, and which will not fully be explained for some chapters to come. But straightforward cases are easy to write, if only by imitating the following examples. Here we make the Cloaked Villain invariably conceal anything she is holding or wearing: Rule for deciding the concealed possessions of the Cloaked Villain: yes. At which point we think about it more carefully, and then rewrite: Rule for deciding the concealed possessions of the Cloaked Villain: if the particular possession is the sable cloak, no; otherwise yes. Parts are treated exactly as if clothes or items being held, and the following will make the face and inscription on a coin invisible unless the player is holding it - the idea being that they are too small to be seen from farther away. The coin is in the Roman Villa. The face and inscription are parts of the coin. Rule for deciding the concealed possessions of the coin: if the coin is carried, no; otherwise yes. There is also an either/or property called "described"/"undescribed", intended to be used only as a last resort, but which has the ability to hide something from room descriptions. This not really hiding: the idea is that "undescribed" should be used only for cases where some other text already reveals the item, or where its presence is implicit. Even then, it should only be used when the item is intended to be taken or moved by the player at some point - if the item isn't intended to move, it's much better to make it "scenery". (There's only one commonly-found example - the player's own body, the "yourself", is undescribed.) Note that the "undescribed" property is automatically removed from anything carried by, worn by or part of the player, even indirectly; and that nothing on top of an "undescribed" supporter will be visible in a room description, even if it itself is "described". (Scenery supporters don't suffer from that restriction, which is one reason scenery is a better option when possible.) Example 36 (***): Search and Seizure A smuggler who has items, some of which are hidden. 3.25. The location of something The model world created by Inform is partitioned into rooms. This means that everything which exists in the model world, exists in one of the rooms. If we write a sentence such as Professor Wilderspin is a man. and say nothing more about Wilderspin, then he does not physically exist at the start of the game: he is said to be "out of play", and stays that way until we move him into one of the rooms. A better metaphor might be that he is waiting in the wings, ready to come onto the stage. Every thing is either out of play, or can be found in one of the rooms, and the property "location of X" gives us the room in question. The following condition tests, in effect, whether Wilderspin is in play: if the location of Wilderspin is a room, ... Which uses a new phrase:

location of (object) ... room
This phrase produces the room which, perhaps indirectly, contains the object given. Example: if the player stands in Biblioll College and wears a waistcoat, inside which is a fob watch, then location of the fob watch is Biblioll College. In general, a thing cannot be in two rooms at once, but there are two exceptions: two-sided doors, present on both sides, and backdrops. The "location of" a door is its front side, but a backdrop has no location. (Objects which are not things at all, such as rooms and directions, also have no location.)
We very often want to know the location of the player, and this is more simply called just "the location". (This is actually a value that varies rather than a phrase, but that's a technicality we can ignore here.) The idea of indirect containment is useful enough to have a name: Inform calls it "enclosure". A thing encloses whatever is a part of itself, or inside itself, or on top of itself, and it also encloses anything that they enclose. And when something moves around, anything it encloses will move with it. In the example above, Biblioll College (a room) and the player (a person) both enclose the fob watch and the waistcoat. (The small print: a door is enclosed by the rooms on both sides; a backdrop is never enclosed.) Enclosure is only useful when being used as a question. So the following is fine: if the player encloses the fob watch, ... But these will produce problem messages: The player encloses the fob watch. The location of the trilobite is the Museum. because they are too vague. Inform needs to know exactly where the fob watch and the trilobite will begin the game, whereas these sentences leave room for doubt about who or what is actually holding them. (Beta release note) Previous builds allowed the following abbreviation:

if in (object):
This condition is true if the location of the player is the given room. Example: if in Biblioll College, ... This is being withdrawn, as too often unclear. Instead, write "if the location is Biblioll College".
Example 37 (**): Van Helsing A character who approaches the player, then follows him from room to room. 3.26. Directions "Direction" is a kind which is quite unlike most of those seen so far. While it has to do with the physical world, a direction does not exactly belong to it. One cannot find "southeast" sitting on a shelf. "Direction" is not a kind of thing, nor a kind of room: it is a kind in its own right. Every direction has an "opposite" property, which is always another direction. These occur in matched pairs. The opposite of north is south, just as the opposite of south is north. The opposite of southeast is northwest, the opposite of inside is outside, and so on. When Inform reads a sentence like... Bangkok is south of Nakhon Sawan. ...it assumes that the opposite map connection is probably also valid, so that Nakhon Sawan is north of Bangkok. The chapter began with the twelve directions built into Inform: north, northeast, east, southeast, south, southwest, west, northwest, up, down, inside, outside But the built-in set is not always appropriate. Sometimes this is too many; if we wanted to write about a Flatland, for instance, then up and down ought to go. But in practice it is better not to abolish them as directions but instead to forbid travelling in them. (See the Recipe Book for examples.) But away from our familiar Earth, the usual frame of reference loses its meaning. Terry Pratchett's "Discworld" comedies, set on a rotating disc, use the directions turnwise, widdershins, hubwards and rimwards. On board a Zeppelin airship, which constantly changes its course, the cockpit has no fixed compass bearing from the passenger cabin: it is not very naturally "north". In zero gravity, there is no up or down. Mars does not have a magnetic core, so a compass doesn't work there. New directions must always be created in opposing pairs, and each must be declared with a clear simple sentence of the form "X is a direction." For instance: Turnwise is a direction. The opposite of turnwise is widdershins. Widdershins is a direction. The opposite of widdershins is turnwise. Hubwards is a direction. The opposite of hubwards is rimwards. Rimwards is a direction. The opposite of rimwards is hubwards. It is then possible to write, say, that: Ankh-Morpork is hubwards of Lancre and turnwise from Borogravia. Of course the World page of the Index for the project normally draws a map based on compass bearings, so it will get a little befuddled by this. But the map drawn in the Index can be given hints to improve its legibility. More on this later, but for now note that Index map with turnwise mapped as east. maps turnwise directions as if they were east, that is, pointing rightwards on the page. (This has no effect on the story file produced; it does not mean turnwise is simply a new name for east; it affects only the look of the Index map, which is only a convenience for the author in any case.) At one time, directions had to have shortish names (up to three words only), but that's no longer true: Just the tiniest smidge off magnetic north is a direction. The opposite of just the tiniest smidge off magnetic north is just the tiniest smidge off magnetic south. Just the tiniest smidge off magnetic south is a direction. The opposite of just the tiniest smidge off magnetic south is just the tiniest smidge off magnetic north. Example 38 (**): Prisoner's Dilemma A button that causes a previously non-existent exit to come into being. Example 39 (**): The World of Charles S. Roberts Replacing the ordinary compass bearings with a set of six directions to impose a hexagonal rather than square grid on the landscape. Example 40 (***): Fore Understand "fore", "aft", "port", and "starboard", but only when the player is on a vessel. 3.27. Review of Chapter 3: Things 1. Inform turns our description of the initial situation into a model world, in which the places and items important to the story are objects. These objects come in different kinds. In the course of Chapter 3, we have seen all of the kinds of object built into Inform. If we turn to the Kinds tab in the Index of any project, we can see these kinds set out: room thing door container player's holdall vehicle supporter backdrop person animal man woman device direction region 2. Inform automatically creates a person, called "yourself", and some directions - north, east, south, and so on - but nothing more. We are allowed to create instances of any kind, including more people and further directions (though directions have to be created in opposite pairs). The only absolute requirement is that we must create at least one room, so that the player can begin somewhere. Sometimes we explicitly declare the kind of something, as here: In the Counting House is a device called the clockwork register. But Inform also deduces kinds from context. For instance, from The Royal Treasury is north of the Counting House. The glass vase is on the mantelpiece. Inform deduces that the Treasury and Counting House have kind "room", and that the mantelpiece is a "supporter". 3. All these objects are related in order to make up the model world. The map lays out the rooms with connections between them, each in its own direction. A map connection either connects two rooms, or one room and one door. Inform assumes that map connections are two-way unless told otherwise. We can see the map for a project using the World index. A door is normally present in two rooms at once, and connected to each as part of the map: The red door is north of the Counting House and south of the Treasury. A backdrop is a piece of scenery which can be touched by the player, but not picked up or moved, and which is present in several rooms at once. Except for doors and backdrops, a thing can only be in one room at a time. Things can then be in rooms or containers; on supporters; part of other things; or carried by or worn by people. (We shall see how to create new relations in the chapter on Relations: this will allow us to make much more subtle, or conceptually different, model worlds.) 4. The Kinds index tells us that things are Normally unlit not lit, inedible not edible, opaque not transparent, described not undescribed, portable not fixed in place, unmarked for listing not marked for listing. Lit things give light to their surroundings; unlit things do not. Edible things can be eaten by the player, and when this happens they vanish from the game world. Transparent things - usually containers - reveal their contents even when closed, and allow light to pass through. Portable things can be carried. (The "described" and "marked for listing" properties are not relevant for setting up the world, but are instead used in play to organise room descriptions: see the chapter on Activities.) The Kinds index continues with the information that things are Not normally enterable, scenery, wearable, handled, pushable between rooms, mentioned. Enterable things respond to ENTER or SIT ON, and are usually either containers or supporters. Scenery cannot be picked up, and is not included in the You can see... paragraph which sometimes concludes a room description: it is best used for items which are named in the room's description. Wearable things are those which can be worn by people: Inform assumes that anything worn at the start of play is wearable. Things pushable between rooms respond to such commands as PUSH CART WEST. ("Handled" and "mentioned" are, again, to do with behaviour in play: something is handled once it has been taken for the first time; "mentioned" is used in constructing room descriptions.) 5. Moving on to properties with values, a thing Can have description, printed name, initial appearance, printed plural name, indefinite article. The description is what we see after "LOOK AT THING", and the initial appearance, if provided, is a paragraph about the object that will appear in the room description where the object is (provided it has never been taken - hence "initial"). The printed name is the name used in all sentences such as You can see a dog here... and the printed plural name is used when the item is one of several of the same kind, as in You can see seven dogs here. It is usually not necessary to set these by hand, though occasionally if we have items oddly named it is worth doing so. (We can also override these entirely with more complicated instructions using the "printing the name..." and "printing the plural name..." activities described later.) Likewise Inform will do its best to assign a sensible indefinite article ("a" or "some" by default), but we can override its opinions and set this ourselves, for items such as "your mother". Calling an object "Some bread..." or similar at the first mention will establish that that object is to be considered as grammatically plural. Saying something like "a thing called the door" will indicate that the door should always be called "the" and never "a"; and leaving off the article entirely will prevent one from being printed afterward, as Inform decides that the object has a proper name like Matilda or Jerome. 6. Other kinds have additional properties: containers and doors can be open or closed, locked or unlocked, lockable or not lockable, all of which have the meanings we might expect. We may give something its own key by saying, for instance, The blue key unlocks the grey door. Devices may be switched on or switched off, though we will have to add our own instructions about what they do when these conditions pertain. Containers, supporters, and people may be assigned a carrying capacity, determining how many things they are allowed to contain, support, or possess; things worn are not counted towards the carrying capacity of a person. 7. Rooms may be lighted or dark, visited or unvisited. The former we may set ourselves at the outset of play, and it will not change unless we say so. (Whether there is actually darkness in a "dark" room depends on the circumstances: a player who takes a lit candle into the room will be able to see.) The visited property is used by Inform to keep track of whether or not the player has been to any given room, or - to be more specific - whether the player has ever completed a LOOK action in that room. Therefore, if we ask if the Lawn Furniture Sales Department is visited... the answer will be "no" up to and during the first printing of the room's description, and "yes" forever thereafter. Chapter 4: Kinds 4.1. New kinds Values are to Inform what nouns are to English sentences. They represent numbers, times of day, pieces of text, places, people, doors, and so on. Because they have such an enormous variety, and because we often want to talk about what some of them have in common, we need a way to sort all of these different ideas out. That's the main aim of Inform's concept of "kind". Every value has a kind. The kind of 10 is "number"; the kind of 11:30 PM is "time"; the kind of "jinxed wizards pluck ivy from my quilt" is "text"; and so on. The Kinds index panel shows the kinds present in the current Inform project, which will always include a wide range of built-in kinds, and usually also some new ones created in that project. Some kinds are more general than others. For example, if we write: Growler is an animal in the Savannah. then Growler is an "animal", which is a kind of "thing", which is a kind of "object". When we talk about "the" kind of Growler, we mean "animal", the most specific one, but actually he belongs to all of those kinds. As we see from this example, kinds have a whole hierarchy. Some are specialised versions of other kinds; some are not. Browsing the Kinds index shows that Inform builds its model world out of "objects". (That's really what objects are: "object" is a kind of value used to make the ingredients of the model world.) The objects fall into four fundamental kinds, "room", "thing", "direction" and "region", and "thing" is more subdivided still. All the same, Inform starts out with a fairly simple arrangement. Because taxonomy - setting up kinds for everything - is so difficult, and depends so much on what you want it for, Inform creates relatively few kinds in advance: it has "animal" built in, but not "mammal" or "Bengal tiger". When we need more, we must make them ourselves. Let's see how we might invent these new kinds. The easy one is: A Bengal tiger is a kind of animal. Given that, we can then write: Growler is a Bengal tiger in the Savannah. That's easy enough. Adding "mammal" now looks awkward, though, because it seems to belong in between the two. All Bengal tigers are mammals, but not all animals are. But Inform can sort this out: A mammal is a kind of animal. A Bengal tiger is a kind of mammal. If we look at the Kinds index, we should indeed see a hierarchy: object > person > animal > mammal > Bengal tiger though the diagram is laid out as a sort of tree, just as zoologists do. As another example, it may seem curious that Inform doesn't usually think "man" is a kind of "animal". This is really because, in English, people don't usually expect something like "if an animal is in the garden" to be true when it's only the Revd Mr Beebe going for a walk. People expect the word "animal" not to mean a human being, despite our common genetic ancestry. But if we want to rearrange Inform's default ideas, we can do that quite easily: A man is a kind of animal. A woman is a kind of animal. Or indeed we could say: A human being is a kind of mammal. A man and a woman are kinds of human being. While this is an ideal way to make new kinds for the model world, we are more restricted in what we can do outside of objects. For instance, A glob is a kind of number. isn't allowed. The numbers are fixed and all exist already; they aren't like Bengal tigers which we can simply imagine, and fill the world with. "Number" is not a concept we can specialise any further. But what we can do is to invent entirely new concepts, like so: A distance is a kind of value. We will see more of these later. (This isn't specialising anything - "value" is a sort of everything-category, and is too big and vague to be a kind.) Example 41 (**): Vouvray Adding synonyms to an entire kind of thing. 4.2. Using new kinds This seems a good point to see what we can with new kinds. Here we invent a new kind to provide a new sort of room: A dead end is a kind of room. Any dead end that we make is also a room, so it has all of the properties and behaviour of a room. For instance, every room is either "lighted" or "dark", and the default is to be lighted. But we can reverse that convention for dead ends, and we can also fill in some other properties: A dead end is a kind of room with printed name "Dead End" and description "This is a dead end. You'll have to go back the way you came." A dead end is usually dark. The Undertomb is a dark room. East is a dead end. South is a dead end with printed name "Collapsed Dead End". Northwest is a dead end called the Tortuous Alcove. In the Undertomb is the candle lantern. It is lit. As a result of this, three different rooms adjoin the Undertomb, all dead ends. This is much more concise than spelling them out one at a time would be. Inform often doesn't mind in what order it is told about the world, but it may need to know the name of a kind before that kind can be used. For example, A coffer is a kind of container. In the Crypt is an open coffer. makes sense to Inform and results in the creation of a new thing, just called "coffer" in the absence of any other name to give it, whose kind is "coffer" and which is initially open. Whereas if Inform reads: In the Crypt is an open coffer. without knowing that "coffer" is a kind, it simply makes a thing called "open coffer" (and which is not a container). Inform has to be careful like this: English is simply too overflowing with multiple meanings. An "open railway ticket", for instance, is not a "railway ticket" that one can put objects into. 4.3. Degrees of certainty When we write: A dead end is usually dark. we are saying that it will be dark rather than lighted unless we should specify otherwise. So it would be fine to add: The Tortuous Alcove is lighted. because although dead ends are usually dark, this one is evidently an exception. On the other hand, if we had originally written A dead end is always dark. then Inform would not have permitted any exception to be made, and would have reported a problem if we had tried to make the Tortuous Alcove lighted. Besides "usually" and "always", we can also employ "seldom" and "never", which are their negatives. Thus, "never lighted" means the same as "always dark". Example 42 (*): Odin Replacing "You see nothing special..." with a different default message for looking at something nondescript. Example 43 (*): Something Narsty A staircase always open and never openable. 4.4. Plural assertions As the following examples show, sentences can make several assertions at once by using the plural. Suppose we have defined a kind called "high-up fixture", for instance like so: A high-up fixture is a kind of thing. A high-up fixture is usually fixed in place. Then the following sentence creates two such objects and puts them in their place: The high shelf and the skylight window are high-up fixtures in the Lumber Room. since it is equivalent to saying: The high shelf is a high-up fixture. The skylight window is a high-up fixture. The high shelf is in the Lumber Room. The skylight window is in the Lumber Room. Such plurals are allowed in almost any context, and we could even define two kinds at once: Bucket and basket are kinds of container. Inform constructs plurals by a form of Conway's pluralisation algorithm, which is quite good - for example, it gets oxen, geese (but mongooses), sheep, wildebeest, bream, vertebrae, quartos, wharves, phenomena, jackanapes and smallpox correct. But English is a very irregular language, and multiple-word nouns sometimes pluralise in unexpected ways. So we sometimes need to intervene: A brother in law is a kind of man. The plural of brother in law is brothers in law. We are allowed to define more than one plural for the same singular text, and for the names of things, rooms or kinds, all alternative versions will be used interchangeably. (For instance, Inform defines both "people" and "persons" as plurals of "person".) Example 44 (***): Get Me to the Church on Time Using kinds of clothing to prevent the player from wearing several pairs of trousers at the same time. 4.5. Kinds of value So much for making new and more specialised kinds of object - for example, new kinds of room, or new kinds of animal. This allows us to describe the physical world in elegant ways, but what about concepts which aren't so physical? Without getting into philosophy, we can probably agree that numbers like 1, 2, 3, ..., and texts like "Jackdaws love my big sphinx of quartz", are not physical. Inside Inform, those are values, but not objects. Inform already has a good stock of this sort of concept built in, so it may not immediately seem clear why we need to create new ones. But in fact this is very useful. To describe the physical world, we need concepts like (for example) distance and brightness. We want to say that two armchairs are 12 feet apart, or that a given light-bulb is very dim. Here, "twelve feet" and "very dim" are clearly not physical objects; they need to be values, but not objects. As these two examples suggest, sometimes we want a quantitative way to measure things, sometimes not. Thomas Hardy, in his novel "The Return of the Native", writes: When he drew nearer he perceived it to be a spring van, ordinary in shape, but singular in colour, this being a lurid red. Hardy doesn't tell us that the wavelength of the light is 700nm, he tells us that the colour is "lurid red", and we understand. Later in the same chapter, Hardy writes: The loads were all laid together, and a pyramid of furze thirty feet in circumference now occupied the crown of the tumulus. and now we do have a quantitative measurement: thirty feet. This is how people write about the world, and how they read about it. So Inform needs to provide both sorts of measurement. (a) Here is a qualitative example. Suppose we would like a candle lantern to burn down, gradually diminishing in brightness. Then we'll need a way to talk about the current strength of the flame, but only in vague terms. Here goes: Brightness is a kind of value. The brightnesses are guttering, weak, radiant and blazing. "Brightness" is now a kind of value on a par with (for instance) "number" or "text". There are only four possible values, named as above. Kinds of value like this, where there are just a few named possibilities, are extremely useful, as we'll see. (b) Now a quantitative example: Weight is a kind of value. 1kg specifies a weight. The difference here is not the way we create the kind, but the way we tell Inform what the possible values are. Instead of a list, we teach Inform some notation. As a result, "26kg" is now a value, for instance. Quantitative kinds like this are sometimes called "units", because - as in this example - they're often units in the sense of measuring things. Many Inform projects never need units, but they can still be very useful, and they're described in detail in the chapter on "Numbers and Equations". 4.6. Properties again So now we have seen two fundamental ideas: "value" and "kind". We have seen how to make a source text which refers to many values - for example, Growler the Bengal tiger, 23kg, "Collapsed Dead End", blazing, 7, all values of different kinds. But we don't just want to a way to refer to values, we want to lay out facts about them. Inform understands two sorts of fact, which it calls properties and relations. Properties are about single values in isolation: Growler is male. Relations are about how values interact with each other: Growler likes Bambi. (Or would like to eat Bambi, anyway.) Relations are really the central organising idea of Inform, and we've seen them many times already: Growler is in the Savannah. expresses a relation called "containment" between Growler and the Savannah. Much more about this in the chapter on Relations: for now, let's go back to the simpler idea of properties. In Inform terms, a "property" is any fact about a value (other than its kind) which the author is allowed to choose. For example, Growler is an animal. Growler is male. The description of Growler is "What immortal hand or eye could frame thy fearful symmetry?". The first of these sentences talks about Growler's kind, but the other two sentences tell Inform about his properties. Properties are divided into either/or properties - "male" versus "female" - and value properties - such as the description of something, which can be any text. The Kinds index shows which kinds of object are allowed to have properties. Every object is, so there's no problem with Growler. In general, if Inform can find a sensible way to store properties, then it will allow them. But it won't allow (for example) properties of numbers. There are only a finite number of Bengal tigers in the world (fewer than three thousand, alas), so Inform can easily store individual description texts for each one of them. But there are an infinite range of numbers. (Inform does allow adjectives like "even" or "odd" to be used about number - saying "if 7 is odd" is fine, for example - but they are not properties in the Inform sense, because the author doesn't get to choose. The author can choose whether Growler is a male or female tiger, but not whether 7 is an even or an odd number.) 4.7. New either/or properties Properties can't be handed out completely freely. In the previous chapter, we saw that we were allowed to make a chair "portable" and to make a room "dark". But if we try this the other way round, Inform produces a Problem message. This is because every property must be created in a way which lays out what values are allowed to have it. The Standard Rules built into Inform say that A thing can be fixed in place or portable. and as a result it won't allow "The Savannah is portable" because the Savannah is a room, not a thing. We must do the same. To go back to our example "dead end" kind: A dead end is either secret or ordinary. This creates just one new property, not two. The names are taken as the two states of a single either/or property: secret means not ordinary, ordinary means not secret. Alternatively, we could just say: A dead end can be secret. in which case the opposite of "secret" would be "not secret". Now we have a property which can be given to any value of the kind "dead end". We're also free to add to the definitions of kinds which already exist, including those built into Inform: for instance, A room is either indoors or outdoors. If we make the above definitions then all dead ends will be "ordinary" and all rooms "outdoors" unless the source text says otherwise. That is, in the absence of other information it's assumed that an either/or property is not true. We could reverse by writing: A dead end is usually secret. A room is usually indoors. A property can be used by several kinds at once. For example, the built-in either/or property "open" is used by both doors and containers, even though door isn't a kind of container and container isn't a kind of door. In fact, although it's more usual to declare properties for whole kinds, they can actually be given to single values one at a time, if we like: The umbrella is carried by the player. The umbrella can be open. And now the umbrella, which is a thing and not a door or container, can also have the property. Example 45 (**): Change of Basis Implementing sleeping and wakeful states. 4.8. New value properties So much for either/or properties. Now we move on to properties which have values attached. The same principles apply, but the wording is different. For example, A dead end has some text called the river sound. The river sound of a dead end is usually "a faint whispering of running water". The Tortuous Alcove has river sound "a gurgle of running water". The property "river sound" is now applicable only to dead ends, so we would not be allowed to talk about "the river sound of the Savannah", say. Moreover, it's required to hold a piece of text. If we tried the following: The river sound of the Tortuous Alcove is 7. ...then Inform would object, because the number 7 is the wrong kind of value to go into the "river sound" property. If we need a numerical property, we can try this instead: A dead end has a number called the difficulty rating. The Tortuous Alcove has difficulty rating 7. Suppose that we were to add: The Exquisitely Narrow Defile is a dead end. The Defile must have a river sound, of course, because we said that every dead end would have one. We haven't said what that river sound will be, but Inform can work it out, because we did say this: The river sound of a dead end is usually "a faint whispering of running water". If there are no instructions at all about the value of a property, Inform fills in the default value of the appropriate kind - in this case, it would be a blank text. (A table of the kinds which can be used for properties, and their default values, can be found in the Kinds index.) Example 46 (*): Would you...? Adding new properties to objects, and checking for their presence. Example 47 (**): Straw Boater Using text properties that apply only to some things and are not defined for others. 4.9. Using new kinds of value in properties It turns out to be very useful to create a new kind of value, and then create a property to hold it. So useful, in fact, that Inform provides two shortened forms for doing so. Here is the first, and the second (making "conditions") is in the section following. Suppose we go back to our example of the candle lantern whose brightness we have to measure. It's clear that what we want to do is to define: Brightness is a kind of value. The brightnesses are guttering, weak, radiant and blazing. And now we can use the technique of the previous section: The lantern has a brightness called the flame strength. The flame strength of the lantern is blazing. This works very nicely. The "flame strength" property is now only allowed to have one of four values we allowed: guttering light, weak light, radiant light or blazing light. So we have succeeded in recording our measurement. But it seems artificial to call the brightness of the lantern "flame strength", when we could instead simply call it "brightness". Much simpler to write: The lantern has a brightness. The lantern is blazing. Now "brightness" is the name of both the property and the kind of value. What's particularly nice is that we can now use the names of the possible brightnesses - "weak", "blazing" and so on - as adjectives. Inform knows that "The lantern is blazing" must be talking about the brightness property, because "blazing" is a brightness. Now we can improve our dead ends: A dead end is a kind of room with printed name "Dead End" and description "This is a dead end, where crags in the uneven rock are caught by the [brightness of the lantern] flame you hold aloft. Despite [river sound] there is no sign of the stream." A dead end is usually dark. The "[brightness of the lantern]" is printed not as literal text, but as whatever the brightness currently is. (The square brackets mark it as what is called a text substitution, which will be the subject of the next chapter.) So we get something like this: This is a dead end, where crags in the uneven rock are caught by the blazing flame you hold aloft. Despite a faint whispering of running water there is no sign of the stream. So now we have a lantern, which has a brightness as a property. But we can build on this further if we like. A brightness such as "guttering" is a value, so it can have properties in its own right. That can be quite useful, in fact: A brightness can be adequate or inadequate. A brightness is usually adequate. Guttering is inadequate. This is convenient because it divides up the brightnesses: The player carries a book. The description of the book is "[if the brightness of the lantern is adequate]Many secrets are now yours.[otherwise]No, the print's too tiny by this awful light." And while we're at it, let's give each brightness its own corresponding temperature: Temperature is a kind of value. 100C specifies a temperature. A brightness has a temperature. The temperature of a brightness is usually 700C. The temperature of blazing is 1400C. The temperature of radiant is 1100C. The description of the lantern is "The lantern shines with a flame at [temperature of the brightness of the lantern]." (Candle flames are hotter than most people think.) (See Text with substitutions for more on varying what is printed.) Example 48 (*): The Undertomb 1 A small map of dead ends, in which the sound of an underground river has different strengths in different caves. Example 49 (**): The Undertomb 2 Flickering lantern-light effects added to the Undertomb. Example 50 (***): Signs and Portents Signpost that points to various destinations, depending on how the player has turned it. Example 51 (***): The Crane's Leg 1 A description text that automatically highlights the ways in which the object differs from a standard member of its kind. 4.10. Conditions of things Now for an even more abbreviated way to create a new kind of value, and at the same time create a property to hold it. Suppose we have something, say a wine cask, which we know is always in one of three different states. We can write: The cask is either customs sealed, liable to tax or stolen goods. This is just like our example of the lantern having possible brightnesses, but it's quicker to do, because we don't need to create or name the kind of value. (The trade-off is that we can't use it for anything else as well.) Initially the cask will be "customs sealed", the first value we gave. We could now write, for instance, The description of the cask is "A well-caulked Spanish wine cask. [if liable to tax] It really is a shame to have to pay duty on it!" Or, as a second example, here we're going to allow a whole kind to have the property, not just a single object: Colour is a kind of value. The colours are red, green and white. A colour can be bright, neutral or flat. Green is neutral. Now in fact these properties are not anonymous: Inform has worked out names for them, even though we didn't give any. The usual arrangement is that the name is the name of the object with the word "condition" tacked on: for instance, "cask condition". So we could write: The printed name of the cask is "wine cask ([cask condition])". so that sometimes this would be "wine cask (liable to tax)", sometimes "wine cask (stolen goods)" and so on. But only usually, because we might need to define several different conditions of the same thing, and then the names would collide. For instance, suppose we write: A fruit is a kind of thing. A fruit can be citrus, berry, melon, or pome. This makes a property and a kind of value each called "fruit condition". But now suppose we add that: A fruit can be unripened, ripe, overripe, or mushy. This is a quite unrelated property - a fruit could have any combination of these two properties, in fact. Left to itself, Inform will call the second one "fruit condition 2", which isn't really ideal if we ever do need to refer to it in other source text. So we are also allowed to give these conditions names of our own choosing: A fruit can be unripened, ripe, overripe, or mushy (this is its squishiness property). And now the resulting property and kind of value would be called "squishiness". 4.11. Default values of kinds Just about every kind has a "default value". Inform needs this when it knows that something has to be a value of a given kind, but it hasn't been told what the value is. For example, in the previous chapter we saw that every thing has a "description" text, but we also created plenty of things without describing them. So if Inform reads The conference pear is in the bowl. and it isn't told anything else about the pear, what should it set the description of the pear to? The answer is that Inform knows the description has to be a value of the kind "text", so it uses the default value of "text". Not very interestingly, this is just the blank text "". Being uninteresting is exactly the idea, of course. The default number is 0, for instance. (Default values are tabulated in the Kinds index.) It's sometimes useful to be able to refer to the default value of a kind without having to spell out what this is (especially if the kind is something obscure, or we're trying to write a rule for an extension which has to work in situations we don't fully know about).

default value of (name of kind) ... value
Produces the default value of the kind named. Examples: The silver repeater is here. "You catch sight of a silver repeater watch, hands immobile at [default value of time]." produces the output: You catch sight of a silver repeater watch, hands immobile at 9:00 am. because nine in the morning is the default time in Inform. If we have: Brightness is a kind of value. The brightnesses are guttering, weak, radiant and blazing. then "default value of brightness" is guttering, the first brightness created. When it comes to kinds of object, we sometimes have to be a little careful. For example, default value of room is always going to be fine (it's always the first room created in the source text). But default value of vehicle would produce a Problem message if there were no vehicles in the world.
4.12. Values that vary Sometimes a value important to the simulated world will not naturally belong to any thing or room, and should not be kept in a property. For example: The prevailing wind is a direction that varies. The prevailing wind is southwest. Or "which varies" would also be allowed, as would the more traditional computing term "variable": The target score is a number variable. The target score is 23. In fact, we have seen a value that varies already: "location", which holds the room in which the game is presently taking place. It's important to tell Inform what kind of value goes into the variable, as this will ensure that the wrong kind of value is never accidentally put into it. But just as for properties, we do not need to say explicitly what the initial value is: and if we do not, Inform will use the default value for its kind. (See the table in the Kinds index.) We can have variables of any of the kinds of value, including new ones, but should watch out for a potential error. If we write: The receptacle is a container that varies. in a world which has no containers at all, Inform will object, because it will be unable to put any initial value into the receptacle variable. A similar complaint will be made if we write: Colour is a kind of value. The fashionable shade is a colour that varies. without ever having defined any colours. Something else we are not permitted is: The receptacle is an open container that varies. because the openness of a given container may change during play, so that the value in the variable might suddenly become invalid even though the variable itself had not changed. Example 52 (***): Real Adventurers Need No Help Allowing the player to turn off all access to hints for the duration of a game, in order to avoid the temptation to rely on them overmuch. 4.13. Duplicates Although it is only useful to a limited extent, we can make any number of copies of something: "Polygons" A shape is a kind of thing. A square is a kind of shape. A triangle is a kind of shape. The Geometry Lab is a room. In the Geometry Lab are three triangles and two squares. The description "three triangles" makes three identical things, each of the kind "triangle", and similarly for the squares. When the above is compiled, the player can type TAKE TWO TRIANGLES or TAKE ALL THE TRIANGLES and so forth. (The player has to type numbers as words when counting things here: so TAKE SIX TRIANGLES makes sense to Inform but TAKE 6 TRIANGLES doesn't, largely for traditional reasons.) Three caveats. Firstly, a counted-out description like "two squares" is only allowed if it combines a number with the name of a kind which is already known (perhaps modified with adjectives, so "two open doors" is fine). If we say: Two circles are in the Lab. without having defined "circle" as a kind in advance, then only a single object will be created - whose name is "two circles". (This is because many natural names start with numbers: "six of clubs", for instance, referring to a single playing card, or "12 Hollywood Close" meaning a single house. We wouldn't want such names to be misinterpreted.) The second caveat is that excessive duplication is expensive in memory and running time. It is perfectly legal to say In the Lab are 75 triangles. but the resulting game may be a little sluggish: and Inform draws the line at 100, refusing to create more duplicates than that in any single place. If we really need more than about fifty duplicated objects - say, a tombola containing raffle tickets numbered 1 to 1000 - it is usually better to find some less literal way to simulate this: for instance, only having a single raffle ticket, but with a randomly chosen number on it. If there are very many items in the same place, commands like TAKE ALL and DROP ALL may mysteriously not quite deal with all of them - this is because the parser, the run-time program which deciphers typed commands, has only limited memory to hold the possibilities. It can be raised with a use option like so: Use maximum things understood at once of 200. (The default is, as above, 100.) Finally: numbers up to twelve may be written out in words in the source text, but larger ones must be written as numerals. So "twelve" or "12", but "13" only. Example 53 (***): Early Childhood A child's set of building blocks, which come in three different colours - red, green and blue - but which can be repainted during play. 4.14. Assemblies and body parts In the previous chapter, we saw that it was possible to make sub-parts of things. For instance, The white door is in the Drawing Room. The handle is part of the white door. creates a door with an attached handle. But what if we want to say that not just this door, but every door, should have a handle? To do this we first need to create a kind called "handle", since there will clearly need to be many handles. The solution is: A handle is a kind of thing. A handle is part of every door. "Every" is a loaded word and best used sparingly. A sentence like "A handle is part of every handle" would, if taken literally, mean that a handle takes forever to make and is never finished. Inform will reject this, but the moral is clear: we should think about what we are doing with "every". We will usually want to work with smaller collections - not literally every room, but with a whole set of them all the same. We can do that like so: A silver coin is a kind of thing. A banking room is a kind of room. Five silver coins are in every banking room. The effect of sentences like these is to make what we might call "assemblies" instead of single things. When a banking room is created, so are five more silver coins; when a door is created, so is another handle. Such sentences act not only on items created later on in the source text, but also on all those created so far. This is especially useful for body parts. If we would like to explore Voltaire's suggestion that history would have been very different if only Cleopatra's nose had been shorter, we will need noses: A nose is a kind of thing. A nose is part of every person. Of course, if we make an assembly like this then we had better remember that the player is also a person and also gets a nose. In fact slightly odd things can happen if we combine this with changing the identity of the player. This works: Cleopatra is a woman in Alexandria. The player is Cleopatra. A nose is a kind of thing. A nose is part of every person. but if those lines are in reverse order then Cleopatra's nose is assembled before she becomes the player, with the result that it ends up called "Cleopatra's nose" rather than "your nose" in play - which is very regal but probably not what we want. To avoid this, settle the player's identity early on in the source text. All of the assemblies above make objects. Most make these new objects "part of" existing ones, but as we saw, they can also be "in" or "on" them. In fact, though, assemblies work in much more general ways: they can assemble values of almost any kind, placed in almost any relationship. To make use of that, we need to create a new verb, a topic which won't be covered properly until a later chapter, but here goes: A colour is a kind of value. The colours are red, green and blue. Liking relates various people to various colours. The verb to like (he likes, they like, it is liked) implies the liking relation. Every person likes a colour. Now every time a person is created, so is a colour which that person will like. If there are two people in the world, the player and Daphne, then we now have five colours: red, green, blue, Daphne's colour and the player's colour. Alternatively, we can assemble the other way around: A person likes every colour. Now we're telling Inform that every time a colour is made, a new person is also made - someone who will like that colour. So this sentence effectively makes three new people, one who likes red, one who likes green, and one who likes blue. Example 54 (*): Being Prepared A kind for jackets, which always includes a container called a pocket. Example 55 (**): Model Shop An "on/off button" which controls whatever device it is part of. Example 56 (***): The Night Before Instructing Inform to prefer different interpretations of EXAMINE NOSE, depending on whether the player is alone, in company, or with Rudolph the Red-nosed Reindeer. Example 57 (***): U-Stor-It A "chest" kind which consists of a container which has a lid as a supporter. 4.15. Names made in assembly Something skated over in the previous section is the question of how Inform gives names to objects (or other values) it creates in an assembly. The standard thing naming combines the names of what's being assembled. For example: A nose is a kind of thing. A nose is part of every person. Antony and Cleopatra are people. might result in the creation of "Antony's nose", part of Antony, and "Cleopatra's nose", part of Cleopatra. In this way, Inform names the noses after their owners. It will always do this unless there are multiple indistinguishable things being created, as in the "five silver coins are in every banking room" example: those will all just be called "silver coin". A small pitfall of this is that if we write: Marcus Tullius Cicero is a person. then although "Marcus Tullius Cicero's nose" and "Cicero's nose" are both valid names for the consular nose, "Marcus's nose" is not. The standard naming scheme is often about right, but as usual Inform offers a way to improve it in particular cases. For example, if we write: Every room contains a vehicle (called its buggy). then we will find the world full of, say, the Garden buggy, the Patio buggy and so on - instead of the Garden vehicle, the Patio vehicle and so on, which is what we would have had without the "called..." part. Similarly, we could write: A person (called its fan) likes every colour. Every person likes a colour (called his favourite colour). The former would produce new people with names like "Green's fan", whereas the latter would produce new colours with names like "Daphne's favourite colour". So much for an informal description. Here is exactly what Inform does: (1a) If there is a "called..." text, Inform uses it, expanding out "its" (or "his" or "her" or "their") expands out to a possessive form of the name of the owner, so to speak, and "it" (or "he" or "she" or "they" or "him" or "them") to the name itself. (1b) If there's no "called..." text, Inform behaves as if we had written "(called its K)", where K is the name of the kind. (2) If this results in value which isn't an object being given a name which already exists, Inform tacks on a number to force the new name to be different from existing ones: e.g., "Daphne's colour 2", "Daphne's colour 3", ... (The reason that (2) doesn't affect objects is that objects are allowed to have names clashing with other objects, or no name at all, whereas other values have to have names belonging to themselves alone.) 4.16. Postscript on simulation That concludes our tour through the design of the initial state of a simulated world. We have seen how to create rooms and to stock them with containers, supporters, devices, doors, men and women. The player of such a simulation can explore, move things around, open and close certain doors and containers, lock or unlock them provided a suitable key is found, switch machines on or off, and so on. But that is about all. There is as yet no element of surprise, no aim or sense of progress to be earned, and no narrative thread. We have painted the backcloth, and laid out the properties, but the actors have yet to take the stage. 4.17. Review of Chapter 4: Kinds 1. Kinds are fundamental sorts of object. Inform comes with a certain number of kinds, but we can create more. This can help us if we need a number of identical objects, or many items that share a great deal of common behavior. An item may belong to only one primary kind. For instance, if we say Fred is a man. then, because a man is a kind of person, and a person is a kind of thing, Fred will also be understood to be a person and a thing. On the other hand, Fred will not also be a woman, a vehicle, or a container, since those are all incompatible with the "man" kind. 2. When we create a new kind, we can give Inform instructions about properties that belong to things of this kind. The following are equivalent: A box is a kind of container which is closed and openable. A box is a kind of container. A box is usually closed and openable. A box is a kind of container. A box is seldom open and unopenable. Each of these statements instructs Inform that boxes in general have these characteristics, though a particular box might begin the game in a different state, as in The player carries a box which is open. We may also write a more absolute instruction, as in these equivalent lines: A box is a kind of container. A box is always closed and openable. A box is a kind of container. A box is never open and unopenable. These instructions tell Inform that we may never begin play with any box defined to be open, so that this time if our source text includes The player carries a box which is open. we will receive a problem message. Inform attempts to construct the simplest possible model of the world based on the information we provide, and anything we tell it directly will override the other assumptions it might make. Note also that "A box is never open" only specifies that the author may not make the box open at the start of play. The player will still be able to open the box during the game. We may not say, though it might seem natural, A crate is a kind of open container. After "kind of...", only the name of a kind may follow, with no adjectives. (This is because a kind is a permanent affiliation: once a crate, always a crate, and similarly for containers, whereas the adjective "open" describes an either/or property that comes and goes.) We also may not assign "usual" either/or properties to kinds already defined by Inform. For instance, the following would not be effective: A door is usually open. A container is usually openable. 3. In addition to either/or properties (such as open vs. closed), things may have numerical properties (with values such as 10) or textual ones (such as "red"). We may set these as well: The printed name of a box is usually "cardboard box". The printed name of a room is usually "Here". The initial appearance of a person is usually "[printed name] stands nearby, looking gloomy." The description of a container is usually "A grubby box held together with silver tape." The carrying capacity of a container is usually 3. 4. We may not give properties to an object unless we have said that the object can have these properties; so, for instance, Inform would complain if we tried to say Fred is a man. Fred is open. (Inform knows that doors and containers can be open, but it doesn't think men can be.) We may say that a thing or class has an either/or property by saying, for instance, Fred can be open. A man can be open. or, equivalently, Fred can be closed. We may say that something can have a text, value, or thing property by saying A room has a number called size. A supporter has some text called the description from inside. A bus transfer has a time called the expiration time. A liquid has a thing called the source spring. or even A container has a rule called the opening result rule. A prop has a scene called the use scene. We will learn more about rules and scenes later; in practice these are the properties we are least likely to need. (For a full list of all the named kinds of value built in to Inform, see the chapter on extensions.) 5. We may define our own new kinds of value, to represent states of things within our model world. These kinds of value may be used as properties of individual things or of entire kinds. So for instance: Brightness is a kind of value. The brightnesses are dim, shining, and blazing. A lamp is a kind of thing. A lamp has a brightness. A lamp is usually blazing. The hurricane lamp is a lamp. Unless we arrange otherwise, a value property can be referred to simply by the name of the value, as here, "the brightness of the hurricane lamp". If, on the other hand, we wanted to associate two brightnesses with the lamp, we might say A lamp has a brightness called maximum brightness. A lamp has a brightness called current brightness. Now we may no longer add A lamp is usually blazing. since Inform will not know whether "blazing" is meant to be the current brightness of the lamp or the maximum brightness; so we will have to be more specific, as The maximum brightness of a lamp is usually blazing. The maximum brightness of the hurricane lamp is shining. The current brightness of the hurricane lamp is dim. and so on. 6. Once we have made a kind, we may create multiple objects of this type without giving them individual names. For instance, we might say: A coin is a kind of thing. The player carries three coins. A basket is a kind of container. 13 baskets are on the shelf. There are two points to note here. First, numbers over twelve may not be spelled out, and must be given numerically. Second, if we do not define a kind first, The player carries three coins. will instead produce a single object whose name is "three coins". We are also allowed to make general rules about how parts and objects are distributed, so: A nose is a kind of thing. A nose is part of every person. A spray of lavender is a kind of thing. Three sprays of lavender are in every gardening basket. A few restrictions apply here. First, we may not use "room", "supporter", or "container" in these sentences; second, when we say "Three sprays of lavender are in every gardening basket", "spray of lavender" and "gardening basket" must both be names of kinds. Inform will often be able to guess about the correct plural of a given word, but will sometimes need correction: The plural of brother in law is brothers in law. 7. The name of a kind will not automatically be understood to refer to an item of that kind: for instance The glass bottle is a container. will not mean that the glass bottle responds to >TAKE CONTAINER and Philippe is a man in the Botanical Garden. will not allow the player to refer to Philippe as "the man". We can get around this using an instruction from later: Understand "man" as Philippe. Or, more generally, Understand "man" as a man. ...in which case, all men can be referred to as "man". The exception is that if we have created items without giving them names, as in The player carries a container. the name of the item will be the name of its kind, so that in this instance the player will see You are carrying: a container and the game will respond to "TAKE CONTAINER". Example 58 (*): Bic Testing to make sure that all objects have been given descriptions. Example 59 (***): Fallout Enclosure Adding an enclosure kind that includes both containers and supporters in order to simplify text that would apply to both. Chapter 5: Text 5.1. Text with substitutions In the previous chapter, we gave properties to certain kinds of things in order to change their appearance and behaviour, and saw brief glimpses of one of Inform's most useful devices: text substitution. The following gives a more complete example: "The Undertomb" A dead end is a kind of room with printed name "Dead End" and description "This is a dead end. You'll have to go back the way you came, consoled only by [river sound]." A dead end is usually dark. The Undertomb is a dark room. East is a dead end. South is a dead end with printed name "Collapsed Dead End". Northwest is a dead end called the Tortuous Alcove. In the Undertomb is the lantern. It is lit. A dead end has some text called river sound. The river sound of a dead end is usually "a faint whispering of running water". The Tortuous Alcove has river sound "a gurgle of running water". The novelty here is the text in square brackets in the first paragraph. They imply more or less what they would when a journalist is quoting something in a newspaper article. The actual words "river sound" are not part of the text. Instead, when Inform prints up the description of a dead end, it will substitute the appropriate river sound in place of these words. Thus the description of the Collapsed Dead End is "This is a dead end. You'll have to go back the way you came, consoled only by a faint whispering of running water.", whereas the description of the Tortuous Alcove is "This is a dead end. You'll have to go back the way you came, consoled only by a gurgle of running water." As the player explores these dead ends, subtle differences will appear in their room descriptions. 5.2. How Inform reads quoted text Text is so fundamental to Inform that the basics had to be covered back in Chapter 2, so let's begin this new chapter with a recap. Literal text is written in double-quotation marks. It's mostly true that what you see is what you get: the literal text "The Hands of the Silversmith" means just The Hands of the Silversmith But four characters are read in unexpected ways: [, ], ' and ". The rules are as follows: Exception 1. Square brackets [ and ] are used to describe what Inform should say, but in a non-literal way. For example, "Your watch reads [time of day]." might produce Your watch reads 9:02 AM. These are called "text substitutions". They're highly flexible, and they can take many different forms. But as useful as they are, they do seem to stop us from making actual [ and ] characters come through on screen. To get around that:

say "[bracket]"
This text substitution expands to a single open square bracket, avoiding the problem that a literal [ in text would look to Inform like the opening of a substitution. Example: "He [bracket]Lord Astor[close bracket] would, wouldn't he?" prints as "He [Lord Astor] would, wouldn't he?".

say "[close bracket]"
This text substitution expands to a single open square bracket, avoiding the problem that a literal ] in text would look to Inform like the closing of a substitution. Example: "He [bracket]Lord Astor[close bracket] would, wouldn't he?" prints as "He [Lord Astor] would, wouldn't he?".
Exception 2. Single quotation marks at the edges of words are printed as double. So: "Simon says, 'It's far too heavy to lift.'" produces Simon says, "It's far too heavy to lift." This is good because typing a double quotation mark inside the quote wouldn't work - it would end the text then and there. Single quotation marks inside words, such as the one in "it's", remain apostrophes. The rule looks odd at first, but turns out to be very practical. The only problem arises if we need an apostrophe at the start or end of a word, or a double inside one. Again, substitutions can fix this:

say "[apostrophe/']"
This text substitution expands to a single quotation mark, avoiding Inform's ordinary rule of converting literal single quotation marks to double at the edges of words. Example: Instead of going outside, say "Lucy snaps, 'What's the matter? You don't trust my cookin[apostrophe] mister?'" produces: Lucy snaps, "What's the matter? You don't trust my cookin' mister?" A more abbreviated form would be: Instead of going outside, say "Lucy snaps, 'What's the matter? You don't trust my cookin['] mister?'" which has exactly the same meaning.

say "[quotation mark]"
This text substitution expands to a double quotation mark. Most of the time this is unnecessary because of Inform's rule of converting literal single quotation marks to double at the edges of words, so it's needed only if we want a double-quote in the middle of a word for some reason. Example: "The compass reads 41o21'23[quotation mark]E." which produces: The compass reads 41o21'23"E. (Note that ["] is not allowed; a double-quotation mark is never allowed inside double-quoted text, not even in a text substitution.)
Exception 3. Texts which end with sentence-ending punctuation - full stop, question mark, exclamation mark - are printed with a line break after them. So: say "i don't know how this ends"; say "I know just how this ends!"; would come out quite differently - this doesn't affect the appearance of the text, but only the position where the next text will appear. Again, sometimes this is not what we want - the full rules are complicated enough to be worth a whole section later in the chapter. 5.3. Text which names things We can put almost any description of a value in square brackets in text, and Inform will work out what kind of value it is and print something accordingly. (Only almost any, because we aren't allowed to use commas or more quotation marks inside a square-bracketed substitution.)

say "[sayable value]"
or: say "[number]"
This text substitution takes the value and produces a textual representation of it. Most kinds of value, and really all of the useful ones, are "sayable" - numbers, times, objects, rules, scenes, and so on. Example: The description of the wrist watch is "The dial reads [time of day]." Here "time of day" is a value - it's a time that varies, and time is a sayable kind of value, so we might get "The dial reads 11:03 AM."
The values we say most often are objects. If we simply put the name of what we want into square brackets, this will be substituted by the full printed name. We might find: "You admire [lantern]." = "You admire candle lantern." But this reads oddly - clearly "the" or "a" is missing. So the following substitutions are used very often:

say "[a object]"
or: say "[an object]"
This text substitution produces the name of the object along with its indefinite article. Example: Instead of examining something (called the whatever): "You can only just make out [a whatever]." which might produce "You can only just make out a lamp-post.", or "You can only just make out Trevor.", or "You can only just make out some soldiers." The "a" or "an" in the wording is replaced by whatever indefinite article applies, if any.

say "[A object]"
or: say "[An object]"
This text substitution produces the name of the object along with its indefinite article, capitalised. Example: Instead of examining something (called the whatever): "[A whatever] can be made out in the mist." which might produce "A lamp-post can be made out in the mist.", or "Trevor can be made out in the mist.", or "Some soldiers can be made out in the mist." The "A" or "An" in the wording is replaced by whatever indefinite article applies, if any.

say "[the object]"
This text substitution produces the name of the object along with its definite article. Example: Instead of examining something (called the whatever): "You can only just make out [the whatever]." which might produce "You can only just make out the lamp-post.", or "You can only just make out Trevor.", or "You can only just make out the soldiers." The "the" in the wording is replaced by whatever definite article applies, if any.

say "[The object]"
This text substitution produces the name of the object along with its definite article, capitalised. Example: Instead of examining something (called the whatever): "[The whatever] may be a trick of the mist." which might produce "The lamp-post may be a trick of the mist.", or "Trevor may be a trick of the mist.", or "The soldiers may be a trick of the mist." The "The" in the wording is replaced by whatever definite article applies, if any.
This may not look very useful, because why not simply put "the", or whatever, into the ordinary text? The answer is that there are times when we do not know in advance which object will be involved. For instance, as we shall later see, there is a special value called "the noun" which is the thing to which the player's current command is applied (thus, if the player typed TAKE BALL, it will be the ball). So: After taking something in the Classroom: "You find [a noun]." might produce replies like "You find a solid rubber ball.", "You find an ink-stained blouse.", "You find some elastic bands.", or even "You find Mr Polycarp." (the school's pet hamster, perhaps). 5.4. Text with numbers When a numerical value is given in a square-bracketed substitution, it is ordinarily printed out in digits. Thus: "You've been wandering around for [turn count] turns now." might print as "You've been wandering around for 213 turns now.", if the game has been played out for exactly that many commands. But if we prefer:

say "[number in words]"
This text substitution writes out the number in English text. Example: "You've been wandering around for [turn count in words] turns now." might produce "You've been wandering around for two hundred and thirteen turns now." The "and" here is natural on one side of the Atlantic but not the other - so with the "Use American dialect." option in place, it disappears.
Either way, though, there is some risk of the following: You've been wandering around for one turns now. We can avoid this using the special substitution:

say "[s]"
This text substitution prints a letter "s" unless the last number printed was 1. Example: "You've been wandering around for [turn count in words] turn[s] now." produces "... for one turn now." or "... for two turns now." as appropriate. Note that it reacts only to numbers, not to other arithmetic values like times (or, for instance, weights from the "Metric Units" extension).
This only solves one case, but it's memorable, and the case is one which turns up often. Example 60 (***): Ballpark A new "to say" definition which allows the author to say "[a number in round numbers]" and get verbal descriptions like "a couple of" or "a few" as a result. 5.5. Text with lists We often want running text to include lists of items.

say "[list of description of objects]"
This text substitution produces a list, in sentence form, of everything matching the description. Example: "Mr Darcy glares proudly at you. He is wearing [list of things worn by Darcy] and carrying [list of things carried by Darcy]." And, if this were from a dramatisation of the novel by Miss Fielding rather than Miss Austen, we might find: Mr Darcy glares proudly at you. He is wearing a pair of Newcastle United boxer shorts and carrying a self-help book. If the description matches nothing - for instance, if Darcy has empty hands - then "nothing" is printed.
As with all lists in Inform, the serial comma is only used if the "Use serial comma." option is in force. So by default we would get "a fishing pole, a hook and a sinker", rather than "a fishing pole, a hook, and a sinker". We then need variations to add indefinite or definite articles, and to capitalise the first item. For example, "Mr Darcy impatiently bundles [the list of things carried by Darcy] into your hands and stomps out of the room." might result in Mr Darcy impatiently bundles the self-help book and the Christmas card into your hands and stomps out of the room.

say "[a list of description of objects]"
This text substitution produces a list, in sentence form, of everything matching the description. Each item is prefaced by its indefinite article. Example: a maritime bill of lading, some hemp rope and Falconer's Naval Dictionary

say "[A list of description of objects]"
This text substitution produces a list, in sentence form, of everything matching the description. Each item is prefaced by its indefinite article, and the first is capitalised, so that it can be used at the beginning of a sentence. Example: A maritime bill of lading, some hemp rope and Falconer's Naval Dictionary

say "[the list of description of objects]"
This text substitution produces a list, in sentence form, of everything matching the description. Each item is prefaced by its definite article. Example: the maritime bill of lading, the hemp rope and Falconer's Naval Dictionary

say "[The list of description of objects]"
This text substitution produces a list, in sentence form, of everything matching the description. Each item is prefaced by its definite article, and the first is capitalised, so that it can be used at the beginning of a sentence. Example: The maritime bill of lading, the hemp rope and Falconer's Naval Dictionary
So much for articles. A more insidious problem comes with something like this: "The places you can go are [list of rooms]." The trouble is that the list may end up either singular or plural. We might be expecting something like: The places you can go are Old Bailey, Bridget's Flat and TV Centre. But if there is only one room, then the result might be: The places you can go are Bridget's Flat. which is wrong. We can get around this with careful wording and a slightly different substitution: "Nearby [is-are list of rooms]."

say "[is-are list of description of objects]"
This text substitution produces a list, in sentence form, of everything matching the description. The whole list starts with "is" (if there's one item or none) or "are" (more than one). Examples: is marlin-spike are maritime bill of lading, hemp rope and Falconer's Naval Dictionary

say "[is-are a list of description of objects]"
This text substitution produces a list, in sentence form, of everything matching the description. Each item is prefaced by its indefinite article, and the whole list starts with "is" (if there's one item or none) or "are" (more than one). Examples: is a marlin-spike are a maritime bill of lading, some hemp rope and Falconer's Naval Dictionary

say "[is-are the list of description of objects]"
This text substitution produces a list, in sentence form, of everything matching the description. Each item is prefaced by its definite article, and the whole list starts with "is" (if there's one item or none) or "are" (more than one). Examples: is the marlin-spike are the maritime bill of lading, the hemp rope and Falconer's Naval Dictionary

say "[a list of description of objects including contents]"
This text substitution produces a list, in sentence form, of everything matching the description, noting any contents in brackets. This is really intended only to be used by the Standard Rules.
(Beta release note) Previous builds allowed this:

say "[contents of object]"
or: say "[the contents of object]"
This text substitution produces a list in sentence form of what is inside the object according to the object tree. Example: "Mr Darcy impatiently bundles [the contents of Darcy] into your hands and stomps out of the room." This is now deprecated - it's much better to use "[list of things carried by Darcy]", which is explicit about the relationship (carrying).
Example 61 (*): Control Center Objects which automatically include a description of their component parts whenever they are examined. Example 62 (**): Tiny Garden A lawn made up of several rooms, with part of the description written automatically. 5.6. Text with variations Text sometimes needs to take different forms in different circumstances. Perhaps it needs an extra sentence if something has happened, or perhaps only one altered word.

say "[if a condition]"
This text substitution produces no text. It's used only for a side-effect: it says that the text following should be said only if the condition is true. That continues until the end of the text, or until an "[end if]" substitution, whichever comes first. If the "[otherwise]" and "[otherwise if]" substitutions are also present, they allow alternatives to be added in case the condition is false. Example: The wine cask is a container. The printed name of the cask is "[if open]broached, empty cask[otherwise]sealed wine cask". we find that the cask is described as "a broached, empty cask" when open, and "a sealed wine cask" when closed. A longer example which begins and ends with fixed text, but has two alternatives in the middle: The Customs Wharf is a room. "Amid the bustle of the quayside, [if the cask is open]many eyes stray to your broached cask. [otherwise]nobody takes much notice of a man heaving a cask about. [end if]Sleek gondolas jostle at the plank pier."

say "[unless a condition]"
This text substitution produces no text. It's used only for a side-effect: it says that the text following should be said only if the condition is false. That continues until the end of the text, or until an "[end if]" substitution, whichever comes first. If the "[otherwise]" and "[otherwise if]" substitutions are also present, they allow alternatives to be added in case the condition is true. Example: The Customs Hall is a room. "With infinite slowness, with ledgers and quill pens, the clerks ruin their eyesight.[unless the player is a woman] They barely even glance in your direction."

say "[otherwise]"
or: say "[else]"
This text substitution produces no text, and can be used only following an "[if ...]" or "[unless ...]" text substitution. It switches from text which appears if the condition is true, to text which appears if it is false. Example: The wine cask is a container. The printed name of the cask is "[if open]broached, empty cask[otherwise]sealed wine cask".

say "[end if]"
This text substitution produces no text, and can be used only to close off a stretch of varying text which begins with "[if ...]".

say "[end unless]"
This text substitution produces no text, and can be used only to close off a stretch of varying text which begins with "[unless ...]".

say "[otherwise/else if a condition]"
This text substitution produces no text, and can be used only following an "[if ...]" or "[unless ...]" text substitution. It gives an alternative text to use if the first condition didn't apply, but this one does. Example: The wine cask is a container. The printed name of the cask is "[if open]broached, empty cask[otherwise if transparent]sealed cask half-full of sloshing wine[otherwise]sealed wine cask".

say "[otherwise/else unless a condition]"
This text substitution produces no text, and can be used only following an "[if ...]" or "[unless ...]" text substitution. It gives an alternative text to use if the first condition didn't apply, and this one is false too.
We sometimes need to be careful about the printing of line breaks: The Cell is a room. "Ah, [if unvisited]the unknown cell. [otherwise]the usual cell." This room description has two possible forms: "Ah, the unknown cell. ", at first sight, and then "Ah, the usual cell." subsequently. But the second form is rounded off with a line break because the last thing printed is a ".", whereas the first form isn't, because it ended with a space. The right thing would have been: The Cell is a room. "Ah, [if unvisited]the unknown cell.[otherwise]the usual cell." allowing no space after "unknown cell." Example 63 (*): When? A door whose description says "...leads east" in one place and "...leads west" in the other. Example 64 (***): Persephone Separate the player's inventory listing into two parts, so that it says "you are carrying..." and then (if the player is wearing anything) "You are also wearing...". Example 65 (***): Whence? A kind of door that always automatically describes the direction it opens and what lies on the far side (if that other room has been visited). 5.7. Text with random alternatives Sometimes we would like to provide a little quirky variation in text, especially in messages which will be seen often. We can achieve this with the "[one of]... [or] ... [or] ..." construction.

say "[one of]"
This text substitution produces no text. It's used only for a side-effect: it switches between a number of alternative texts, which follow it and are divided by "[or]" substitutions, according to a strategy given in a closing substitution. Example: "You flip the coin. [one of]Heads[or]Tails[purely at random]!" Here there are just two alternatives, and the strategy is "purely at random". Exactly half of the time the text will be printed as "You flip the coin. Heads!"; and the other half, "You flip the coin. Tails!".

say "[or]"
This text substitution produces no text, and can be used only in a "[one of]..." construction. It divides alternative wordings. Example: "You flip the coin. [one of]Heads[or]Tails[purely at random]!"
There are seven possible endings, each making the choice of which text to follow in a different way:

say "[purely at random]"
This text substitution produces no text, and can be used only to end a "[one of]..." construction. It indicates that the alternatives are chosen uniformly randomly.

say "[then purely at random]"
This text substitution produces no text, and can be used only to end a "[one of]..." construction. It indicates that the alternatives are chosen in sequence until all have been seen, but that after that they are chosen uniformly randomly.

say "[at random]"
This text substitution produces no text, and can be used only to end a "[one of]..." construction. It indicates that the alternatives are chosen at random except that the same choice cannot come up twice running. This is useful to avoid the deadening effect of repeating the exact same message. Example: "The light changes randomly again; now it's [one of]green[or]amber[or]red[at random]." Here we can safely say the light "changes", because the new colour cannot be the same as the one printed the last time.

say "[then at random]"
This text substitution produces no text, and can be used only to end a "[one of]..." construction. It indicates that the alternatives are chosen in sequence until all have been seen, and then after that, at random except that the same choice cannot come up twice running. Example: "Maybe the murderer is [one of]Colonel Mustard[or]Professor Plum[or]Cardinal Cerise[then at random]."

say "[sticky random]"
This text substitution produces no text, and can be used only to end a "[one of]..." construction. It indicates that a random choice is made the first time the text is printed, but that it sticks from there on. Example: "The newspaper headline is: [one of]War Casualties[or]Terrorists[or]Banks[sticky random] [one of]Continue To Expand[or]Lose Out[sticky random]." Although the newspaper headline will change with each playing, it will not alter during play.

say "[as decreasingly likely outcomes]"
This text substitution produces no text, and can be used only to end a "[one of]..." construction. It indicates that the alternatives are chosen at random, except that the first is most likely to be chosen, the second is next most likely, and so on down to the rarest at the end. Example: "Zorro strides by, [one of]looking purposeful[or]grim-faced[or]deep in thought[or]suppressing a yawn[or]scratching his ribs[or]trying to conceal that he has cut himself shaving[as decreasingly likely outcomes]." There are six outcomes here: the first is six times as likely as the last, and those in between are similarly scaled, so Zorro cuts himself shaving only once in 21 tries, while he looks purposeful almost a third of the time.
But suppose we want to tuck some useful information in these messages, and we want to be sure that the player will see it. Because all of the above options involve randomness, it's possible that an unlucky player might miss a clue placed into only one variant of the message. One fix for this is to make sure that everything turns up sooner or later:

say "[in random order]"
This text substitution produces no text, and can be used only to end a "[one of]..." construction. A random order is chosen for the alternative passages of text, and they are used in that order as the text is printed again and again. When one random cycle finishes, a new one begins. The effect is somewhat like the "shuffle album" feature on an iPod. Example: "You dip into the chapter on [one of]freshwater fish[or]hairless mammals[or]extinct birds[or]amphibians such as the black salamander[in random order]." One small restriction: if there are more than 32 variations, purely random choices will be printed, and there will be no guarantee that repeats are prevented.
Another fix is to avoid randomness altogether:

say "[cycling]"
This text substitution produces no text, and can be used only to end a "[one of]..." construction. It indicates that the alternatives are used one at a time, in turn: after the last one is reached, we start again from the first. Example: "The pundits discuss [one of]the weather[or]world events[or]celebrity gossip[cycling]."

say "[stopping]"
This text substitution produces no text, and can be used only to end a "[one of]..." construction. It indicates that the alternatives are used one at a time, in turn: once the last one is reached, it's used forever after. Example: "[one of]The phone rings[or]The phone rings a second time[or]The phone rings again[stopping]."
Finally, here's a convenient shorthand for one of the commonest things needed:

say "[first time]"
or: say "[only]"
This pair of text substitutions causes whatever is between them to be printed only the first time the text is printed. Example: "The screen door squeaks loudly as when you open it. [first time]Well, you'll get used to it eventually. [only]" This is exactly equivalent to "The screen door squeaks loudly as when you open it. [one of]Well, you'll get used to it eventually. [or][stopping]"; but easier to read.
Example 66 (*): Radio Daze A radio that produces a cycle of output using varying text. Example 67 (**): Camp Bethel Creating characters who change their behavior from turn to turn, and a survey of other common uses for alternative texts. 5.8. Line breaks and paragraph breaks Inform controls the flow of text being said so that it will read, to the player, in a natural way. There are two principles: (a) pieces of text ending with full stop, exclamation or question marks will be followed by line breaks (or "new lines", as some computer programming languages would call them); and (b) pieces of text produced by different rules in Inform will be separated by paragraph breaks. The effect is that authors can forget about paragraph spacing most of the time, but the mechanism is not impossible to fool, so text substitutions are provided to override the usual principles. First, to manipulate line breaks:

say "[line break]"
This text substitution produces a line break. Example: "There is an endless sense of[line break]falling and[line break]falling." Line breaks are not paragraph breaks, so the result is: There is an endless sense of falling and falling. with no extra vertical spacing between these lines.

say "[no line break]"
This text substitution produces no text. It's used only for a side-effect: it prevents a line break where Inform might otherwise assume one. Example: "The chorus sing [one of]Jerusalem[or]Rule, Britannia![no line break][at random]." Here the "[no line break]" stops Inform from thinking that the exclamation mark means a sentence ending - it's part of the name of the song "Rule, Britannia!". So we get The chorus sing Rule, Britannia!. with no line break between the "!" and ".".
And similarly for paragraph breaks. Because Inform can be pretty trigger-happy with these, the first need is for a way to stop them:

say "[run paragraph on]"
This text substitution produces no text. It's used only for a side-effect: it prevents a paragraph break occurring after the present text is printed, in case Inform might be tempted to place one there. Example: Before taking something, say "Very well. [run paragraph on]". This allows the reply to, say, TAKE ENVELOPE to be Very well. Taken. rather than Very well. Taken. which is how texts produced by different rules would normally be shown. (It's a traditional printer's term. See Oldfield's Manual of Typography, 1892, under "When two paragraphs are required to be made into one, or, in technical language, 'to run on'.")
But sometimes we actually want paragraph breaks in unexpected places. One way is to force them outright:

say "[paragraph break]"
This text substitution produces a paragraph break. Example: "This is not right.[paragraph break]No, something is terribly wrong." Paragraph breaks have a little vertical spacing in them, unlike mere line breaks, so the result is: This is not right. No, something is terribly wrong.
More subtly, we can give Inform the option:

say "[conditional paragraph break]"
This text substitution either produces a paragraph break, or no text at all. It marks a place where Inform can put a paragraph break if necessary; in effect it simulates what Inform does every time a "before" or similar rule finishes. If there is text already printed, and text then follows on, a paragraph break is made. But if not, nothing is done. This is sometimes useful when producing a large amount of text which changes with the circumstances so that it is hard to predict in advance whether a paragraph break is needed or not.
Really finicky authors might possibly want to know this:

if a paragraph break is pending:
This condition is true if text has recently been said in such a way that Inform expects to add a paragraph break at the next opportunity (for instance when the present rule ends and another one says something, or when a "[conditional paragraph break]" is made).
Finally, there are two special sorts of paragraph break for special circumstances. They are mainly used by the Standard Rules, and imitate the textual layout styles of traditional IF.

say "[command clarification break]"
This text substitution produces a line break, and then also a paragraph break if the text immediately following is a room description brought about by having gone to to a different room and looking around, in which case a line break should be added. In traditional IF, this is used when clarifying what Inform thinks the player intended by a given command. Example: say "(first opening [the noun])[command clarification break]"; might result in (first opening the valise) You rummage through the valise for tickets, but find nothing.

say "[run paragraph on with special look spacing]"
This text substitution produces no text. It's used only for a side-effect: it indicates that the current printing position does not follow a skipped line, and that further material is expected which will run on from the previous paragraph, but that if no further material turns up then a skipped line would be needed before the next command prompt. (It's very likely that only the Standard Rules will ever need this.)
Example 68 (**): Beekeeper's Apprentice Making the SEARCH command examine all the scenery in the current location. 5.9. Text with type styles Inform does not go in for the use of fonts: a work of IF will be rendered with different fonts on different machines anyway, from tiny personal organisers up to huge workstations. However, it does allow for a modest amount of styling.

say "[bold type]"
This text substitution produces no text. It's used only for a side-effect: to make the text following it appear in bold face. "[roman type]" should be used to switch back to normal. Example: "Jane looked down. [bold type]Danger[roman type], the sign read."

say "[italic type]"
This text substitution produces no text. It's used only for a side-effect: to make the text following it appear in italics. "[roman type]" should be used to switch back to normal. Example: "This is [italic type]very suspicious[roman type], said Peter."

say "[roman type]"
This text substitution produces no text. It's used only for a side-effect: to return to ordinary Roman type after a previous use of "[bold type]" or "[italic type]".
but there is one other effect we can employ:

say "[fixed letter spacing]"
This text substitution produces no text. It's used only for a side-effect: to make the text following it appear with fixed letter spacing. In variable letter spacing, a lower case "m" is much wider than an "l", which is natural to the eye since it has been printing practice since the Renaissance. Fixed letter spacing is more like typewriting, and it is best used to reproduce typewritten text or printed notices; it can also be convenient for making simple diagrams. Example: "On the door is written: [fixed letter spacing]J45--O-O-O[variable letter spacing]."

say "[variable letter spacing]"
This text substitution produces no text. It's used only for a side-effect: to return to ordinary letter spacing after a previous use of "[fixed letter spacing]".
Whichever effect we use (and they can be combined), we should be careful to ensure that we return to normal -- roman type and variable letter spacing -- after any specially-treated text has been printed. Example 69 (*): Garibaldi 2 Adding coloured text to the example of door-status readouts. 5.10. Accented letters Inform 7 is infused by the English language and for the present it would be difficult to write a work of IF in any other language with it. (Inform 6 remains a practical tool for non-English IF, though, having been translated into French, Italian, Spanish, German, and a number of other languages.) But even a book in English contains occasional quotations or words borrowed from other tongues, so we are going to need more than plain A to Z. The world has a bewildering range of letters, accents, diacritics, markers and signs. Inform tries to support the widest range possible, but the works of IF produced by Inform are programs which then have to be run on a (virtual) computer whose abilities are more constrained: few players will have an Ethiopian font installed, after all. So a degree of caution is called for. (a) Definitely safe to use. Inform's highest level of support is for the letters found on a typical English typewriter keyboard, including both the $ and £ signs (but not the Yen or Euro symbols ¥ and €), and in addition the following: ä, á, à, ã, å, â and Ä, Á, À, Ã, Å,  ë, é, è, ê and Ë, É, È, Ê ï, í, ì, î and Ï, Í, Ì, Î ö, ó, ò, õ, ø, ô and Ö, Ó, Ò, Õ, Ø, Ô ü, ú, ù, û and Ü, Ú, Ù, Û ÿ, ý and Ý (but not Ÿ) ñ and Ñ ç and Ç æ and Æ (but not œ or Œ) ß ¡, ¿ These characters can be typed directly into the Source panel, and can be used outside quotation marks: we can call a room the Église, for instance. (b) Characters which can safely be used, but will be simplified. As it reads in the text, Inform silently converts all kinds of dash (en-rules, em-rules, etc.) to simple hyphens, all kinds of space other than tabs (em-spaces, non-breaking spaces, etc.) to simple spaces, and all kinds of quotation marks to "straight" (non-smart) marks. (c) Characters which can be used provided they are in quoted text, and which will probably but not certainly be visible to the player. All other Latin letter-forms, including the œ ligature, East European forms such as ő, ş and ž, and Portuguese forms such as ũ; the Greek and Cyrillic alphabets, with their associated variants and accents; and the principal currency symbols, such as € and ¥. Such characters are not legal in unquoted text: so we could write The Churchyard is a room. The printed name of the Churchyard is "Łodz Churchyard". but not Łodz Churchyard is a room. Moreover, the player is not allowed to type these characters in commands during play: or rather, they will not be recognised if he does. They are for printing only. (d) Characters which might work, or might not. The Arabic and Hebrew alphabets are fairly likely to be available; miscellaneous symbols are sometimes legible to the player, sometimes not. Other alphabets are chancier still. (If a work of IF depends on these being visible, it may be necessary to instruct players to use specific interpreters, or to provide a way for the player to test that all will be well.) 5.11. Unicode characters As we have seen, Inform allows us to type a wide range of characters into the source text, although the more exotic ones may only appear inside quotation marks. But they become more and more difficult to type as they become more obscure. Inform therefore allows us to describe a letter using a text substitution rather than typing it directly.

say "[unicode character]"
This text substitution produces the Unicode character named (or numbered). Example: "[unicode 321]odz Churchyard" produces a Polish slashed L. If the Unicode Character Names or Unicode Full Character Names extensions are included, characters can also be named as well as numbered: "[unicode Latin capital letter L with stroke]odz Churchyard"
The Unicode standard assigns character numbers to essentially every marking used in text from any human language: its full range is enormous. (Note that Inform writes these numbers in decimal: many reference charts show them in hexadecimal, or base 16, which can cause confusion.) Inform can only handle codes [unicode 32] up to [unicode 65535], so it is not quite so catholic, but the range is still enormous enough that code numbers are unfamiliar to the eye. Inform therefore allows us to use the official Unicode 4.1 names for characters, instead of their decimal numbers, provided we have Included the necessary extension like so: Include Unicode Character Names by Graham Nelson. This extension provides names for some 2900 of the most commonly used characters. It means, for instance, that we can write text such as: "Dr Zarkov unveils the new [unicode Hebrew letter alef] Nought drive." "Omar plays 4[unicode black spade suit] with an air of triumph." Admittedly, these can get a little verbose: "[unicode Greek small letter omega with psili and perispomeni and ypogegrammeni]" But before getting carried away, we should remember the hazards: Inform allows us to type, say, "[unicode Saturn]" (an astrological sign) but it appears only as a black square if the resulting game is played by an interpreter using a font which lacks the relevant sign. For instance, Zoom for OS X uses the Lucida Grande and Apple Symbol fonts by default, and this combination does contain the Saturn sign: but Windows Frotz tends to use the Tahoma font by default, which does not. (Another issue is that the fixed-pitch font, such as used in the status line, may not contain all the characters that the variable-pitch font of the main text contains.) To write something with truly outré characters is therefore a little chancy: users would have to be told quite carefully what interpreter and font to use to play it. The "Unicode Character Names" extension, which is pre-installed in the standard distribution of Inform, defines names for the Latin, Greek, Cyrillic, Hebrew and Braille alphabets, together with currency and miscellaneous other symbols, including some for drawing boxes and arrows. It is only optionally installed because even this is quite large: but in case it should still prove inadequate, an alternative can be used: Include Unicode Full Character Names by Graham Nelson. This includes all 12,997 named characters in the 16-bit range of the Unicode 4.1 standard: it is the size of a small novel and its inclusion will slow Inform down. But if you want to experiment with Arabic, ecclesiastical Georgian, Cherokee, Tibetan, Syriac, the International Phonetic Alphabet, hexagrams or the unified Canadian aboriginal syllabics, "Unicode Full Character Names" (again built into Inform) is the extension for you. Example 70 (***): The Über-complète clavier This example provides a fairly stringent test of exotic lettering. 5.12. Displaying quotations Text is normally printed in between the typed commands of the player, rolling upwards from the bottom of the screen, as if a dialogue is being typed by an old-fashioned teletype. But it can also be displayed in a bolder way, floating above the main text, and this is sometimes used to display quotations.

display the boxed quotation (text)
This phrase displays the given text on screen in an overlaid box. For reasons to do with the way such quotations are plotted onto the screen, their text is treated literally: no substitutions in square brackets are obeyed. The quotation will only ever appear once, regardless of the number of times the "display the boxed quotation ..." phrase is reached. Rather than being shown immediately - and thus, probably, scrolling away before it can be seen - the display is held back until the next command prompt is shown to the player. Example: After looking in the Wabe, display the boxed quotation "And 'the wabe' is the grass-plot round a sun-dial, I suppose? said Alice, surprised at her own ingenuity. Of course it is. It's called 'wabe,' you know, because it goes a long way before it, and a long way behind it -- -- Lewis Carroll". This was the original example used in Trinity, by Brian Moriarty, which invented the idea. A player exploring Kensington Gardens comes upon a location enigmatically called The Wabe; and by way of explanation, this quotation pops up.
This is a simple feature, and we should go in search of a suitable extension for fancier screen effects if we would like to do more. 5.13. Making new substitutions If we have some textual effect which needs to occur in several different messages, we might want to create a new text substitution for it. For instance: The Missile Base is a room. "[security notice]Seems to be a futuristic missile base." M's Office is east of the Missile Base. "[security notice]Admiral Sir M.- M.- glares up from his desk." To say security notice: say "This area is a Prohibited Place within the meaning of the Official Secrets Act 1939. " This is only the tip of the iceberg in how to define ways to do things using "To...", as we shall see. The definition makes "say the security notice" a new phrase known to Inform. A text substitution is exactly a phrase whose name begins with "say" (well - except for the "say" phrase itself), so the effect is that "[security notice]" is a new text substitution. Several of the examples in this chapter make use of this trick. Inform often ignores the casing of the text it reads, but sometimes uses it as a clue to meaning. We have already seen that "[an item]" and "[An item]" produce different results, for instance. Similarly, it's possible to define two text substitutions which are the same except for the initial casing. We might write: To say Security Notice: say "THIS AREA IS A PROHIBITED PLACE WITHIN THE MEANING OF THE OFFICIAL SECRETS ACT 1939. " And now Inform will act on "[Security Notice]" differently from "[security notice]". (See The phrasebook for other forms of phrase besides To say....) Example 71 (*): Fifty Ways to Leave Your Larva Using text substitution to make characters reply differently under the same circumstances. Example 72 (***): Fifty Times Fifty Ways Writing your own rules for how to carry out substitutions. 5.14. Review of Chapter 5: Text 1. In phrases or text to say, text in square brackets will be treated as a substitution. The thing to be said might be the name of an object: say "[a dog]". Text in square brackets might also be a property: The printed name of a lamp is usually "[brightness] lamp". The initial appearance of a person is usually "You notice [the item described]". Here "the item described" refers to whatever object possesses the property in question. 2. Numbers and times of day may also be printed, and some special rules apply: we are allowed to tell Inform to say them "in words". say "[The carpet area of the room]" say "[The number of things carried by the player]" say "[The number of things carried by the player in words]" say "[The expiration time of the bus ticket]" say "[The expiration time of the bus ticket in words]" Times may also be rounded off: say "[The expiration time of the bus ticket to the nearest 20 minutes]" say "[The expiration time of the bus ticket to the nearest 20 minutes in words]" See the chapter on Time for more discussion on representing and calculating times. 3. A text substitution may also be a list of things: say "[the list of royal servants]" say "[a list of containers which contain something]" say "[list of fish without gills]" "[list...]" and "[a list...]" have the same effect, namely to produce a list prefaced with indefinite articles ("a ham, a cabbage, Mr Darcy, some shoelaces..."), while "[the list...]" produces a list prefaced with definite articles ("the ham, the cabbage, Mr Darcy, the shoelaces..."). As we saw in an earlier chapter, lists will be punctuated with the serial comma if we have chosen the appropriate use mode, so a source text which contains the sentence: Use the serial comma. will result in all lists being of the form "Julian, Dick, George, and Anne" rather than "Julian, Dick, George and Anne". 4. We may also use bracketed commands to change the style of text or create breaks in the text layout: say "[italic type]"; say "[roman type]"; say "[bold type]"; say "[line break]"; say "[paragraph break]"; say "[conditional paragraph break]"; say "[run paragraph on]". Moreover, the following special bracketed forms exist to print characters that are otherwise hard to express: say "[bracket]" say "[close bracket]" As we saw in an earlier chapter, the following are occasionally useful when Inform would otherwise make the wrong assumption about whether we want a single or a double quote mark: say "[apostrophe]" say "[quotation mark]" 5. We may enclose conditions in brackets: The initial appearance of a person is "[The item described] stands here [if the item described is angry]glowering at you[otherwise]looking bored[end if]." Note that we may use [if...], [otherwise], and [end if] in brackets, but it is not safe to nest if conditions. Because one set of [if...][end if] is within another set, the following will not work as we might wish: The description of the chest of drawers is "A handsome set of cherry-wood drawers[if the top drawer is open] with the top drawer open[if the top drawer contains something] and its contents spilling out[end if][end if]." 6. In the event that we need a more complicated say instruction than we can express with a single if/otherwise/else set, we may require a specially-defined text substitution: To say the drawer-state: say "A handsome set of cherry-wood drawers"; if the top drawer is open: say " with the top drawer open"; if the top drawer contains something: say " and its contents spilling out"; say "." This creates the new text substitution "[the drawer-state]". The definition is an example of creating what's called a "phrase" in Inform. Phrases will be the subject of a whole chapter later on, but for now the point to keep in mind is that a phrase whose definition begins with the word "say" creates a new text substitution. 7. The most common European accented letters can be typed directly anywhere in the source text, but more obscure ones can only appear inside quoted text. If we want to avoid typing these directly, we can describe them with the special substitution [unicode ...], where we either give the Unicode number (in decimal) or its (Unicode standard) name. Names can only be used if we have included the extension Unicode Character Names by Graham Nelson; for really obscure names, we need Unicode Full Character Names by Graham Nelson, though having to read this very large extension will slow Inform down. 8. As a special effect, we can create quotations that float in a box near the top of the screen. The way to do this is display the boxed quotation "Last night I dreamt I went to Manderley again."; Text substitutions may not appear in boxed quotations (any square brackets will come out as literal square brackets). The "display the boxed quotation" instruction may be given as part of a rule or phrase, such as "After eating the tainted lobster", and will actually appear to the player just before the next command prompt after the quotation is prepared; a boxed quotation that has been displayed once will not be repeated. If we want to do more exotic effects along these lines, there are extensions that allow more complicated manipulation of the screen. Chapter 6: Descriptions 6.1. What are descriptions? It is in describing circumstances that Inform really capitalises on the concise, expressive power of natural language, and this chapter brings together the facts about "descriptions". The simplest descriptions consist of a noun alone. Some refer to single things ("lantern", or "wine cask"), others to kinds of thing ("dead end" or "container"). But we have also seen adjectives alone: The oaken desk is fixed in place. Here, "fixed in place" is a description which, to Inform's simple-minded grammar, is a single adjective. And of course adjectives and nouns can be combined: The cargo trunk is an openable container. The description "openable container" consists of the noun "container", meaning a kind of thing, and the adjective "openable", which means one of the two possible states of an either/or property held by that thing. As the next chapter will show, rules also make great use of descriptions: Instead of throwing something at a closed openable door, say "Or you could just use the handle like anyone else, of course." We have already seen that we can list the items fitting a given description: "You look down at [the list of things in the basket]." It's also sometimes convenient to count them up:

number of (description of values) ... number
This phrase counts the number of values matching the description, which may of course be 0. Example: number of open doors produces the number of doors, anywhere in the model world, which are currently open. A Problem message is produced if the number is potentially infinite, or impractical to count: for instance, Inform rejects "number of odd numbers".
It is because descriptions are so widely useful that they deserve a chapter of their own, and this is it. 6.2. Adjectives and nouns Descriptions can contain a noun, but need not, and can contain any number of adjectives: supporter = the noun supporter closed = the adjective closed the open wine cask = the adjective open + the noun wine cask something portable = (some) + the noun thing + the adjective portable Note that we are not allowed to have more than one noun in the same description (something English occasionally does allow as a coded form of emphasis, as in "the man Jenkins" or "the harlot Helen"). Nouns are simple enough, referring either to kinds or specific things. The noun "something" means "some thing", so is actually a reference to the kind "thing". Inform treats this as having the same meaning as "anything", and all told there are eight special nouns of this kind, but with only three different meanings between them: something = anything someone = anyone = somebody = anybody somewhere = anywhere So for instance "anybody male" or "somewhere dark" are valid descriptions. These eight nouns are unusual in being allowed to come at the front of a description: nouns are usually expected to be at the end. (Inform also understands "nothing", "nowhere", "nobody", "no-one" and even "no one", which in a sense are opposites of "something" and the like, but for now we'll look at descriptions of things which do exist rather than don't.) 6.3. Sources of adjectives We have seen two sorts of adjectives so far: those which refer to either/or properties, like "open" and "closed", and those which come out of new kinds of value. If we define Texture is a kind of value. The textures are rough, stubbly and smooth. Everything has a texture. ...then "rough", "stubbly" and "smooth" all become adjectives. (That last sentence "Everything has a texture" was essential, because without it Inform would not know that these words could meaningfully be applied to things.) In addition to these adjectives, we can create new ones (as we shall see), and a few special adjectives such as "visible", "touchable" and "adjacent" are already defined for us by Inform. 6.4. Defining new adjectives Suppose we want to coin a word for supporters currently supporting something. We can do so with the following sentence: Definition: A supporter is occupied if something is on it. Note the colon, which is essential, and the usage of "it" in the definition part to refer to the object in question. (For this purpose we would write "it" even if we were defining a term about, say, a woman instead of a supporter, so that "she" or "her" might seem more appropriate - but see below.) This creates the adjective "occupied", and gives it a definition valid for supporters. That restriction on validity means that non-supporters would always fail the description "something occupied"; which might be unfortunate if we wanted to walk about rooms being occupied. We could give a second definition thus: Definition: A room is occupied if a person is in it. These are entirely different senses of the word "occupied" - a mantelpiece is occupied if an invitation is on it, but for a drawing room to be occupied there must be human presence - and Inform applies whichever sense is relevant when deciding whether or not a given object is "occupied". Often, though not always, we also want to give a name to the opposite possibility. We can do that as follows: Definition: A room is occupied rather than unoccupied if a person is in it. The "rather than..." part of the definition is optional, but it saves having to write a boringly similar definition of "unoccupied" out in longhand. Newly defined adjectives cannot be used when creating things, because they are not explicit enough. Inform could not satisfy: The Ballroom is occupied. The bucket is a large container. because there is not enough information: by whom is the Ballroom occupied? How large, exactly? On the other hand, newly defined adjectives are very helpful in conditions and for rules, as we shall see later on. It is occasionally clumsy having to refer to the subject of a definition using "it". We can avoid this and give the definition better legibility by supplying a name instead. For instance: Definition: a direction (called thataway) is viable if the room thataway from the location is a room. which is a good deal easier to read than Definition: a direction is viable if the room it from the location is a room. (See New conditions, new adjectives for giving more extensive definitions of new adjectives, using phrases.) Example 73 (*): Finishing School The "another" adjective for rules such as "in the presence of another person". 6.5. Defining adjectives for values In general, any noun can have adjectives applied to it, and this means that values can have adjectives just as objects can. We have already seen that they can (in some cases, at least) have either/or properties, and this gives them adjectives just as for objects. But we can also write out definitions which apply to values: Definition: A number is round if the remainder after dividing it by 10 is 0. Definition: A time is late rather than early if it is at least 8 PM. That makes the numbers 20 and 170 but not 37 meet the description "a round number", and the times 8 PM and 11:23 PM but not 9 AM meet the description "a late time". Because they come up fairly often, Inform contains several adjectives for numbers built in: positive - one which is greater than zero (but not 0 itself) negative - one which is less than zero (but not 0 itself) even - a number like ..., -4, -2, 0, 2, 4, ... odd - a number like ..., -5, -3, -1, 1, 3, 5, ... Similarly, two useful adjectives are built in to talk about text: empty - the text "", with no characters in it, not even spaces non-empty - any text which does have at least one character in Adjectives can have multiple definitions and, as long as each applies to a different sort of noun, there will be no problem. We could write: A thing can be round, square or funny-shaped. A container can be odd or ordinary. And these definitions of "round" and "odd" will not interfere with the ones applying to numbers, because Inform can always look at the noun to see which definition is meant in any given case. For instance, if the score is round, ... must mean "round" in the sense of numbers, because the score is a number. Inform itself makes good use of this; "empty" also has meanings applying to rulebooks, lists and activities, for instance, as will be seen later. Although it's more usual to give a definition to apply to a whole kind, we can actually give a specific definition to apply to just a single object or named value. For example: A colour is a kind of value. The colours are red, green and blue. Definition: red is subtle if the player is female. Definition: a colour is subtle if it is blue. The first definition of "subtle" takes precedence, of course, since it has the more specific domain - it applies only to red. The effect of this is that, if the player's female, the subtle colours are red and blue; if not, just blue. Example 74 (***): Only You... Smoke which spreads through the rooms of the map, but only every other turn. 6.6. Whereabouts on a scale? Adjectives are often used in English to give a sense of where something is on a sliding scale. We talk about "a tall man" and "a short man", but without meaning that all men are either tall or short. If pushed, we might say that tall means about 6 feet and up, short means about 5 feet 6 and down, but we more often compare one person's height against another's. Inform allows us to use adjectives in the same way. For example, every container has a number called its "carrying capacity". We can define: Definition: A container is huge if its carrying capacity is 20 or more. Definition: A container is large if its carrying capacity is 10 or more. Definition: A container is standard if its carrying capacity is 7. Definition: A container is small if its carrying capacity is 5 or less. These definitions are similar to those in the previous section, but have a very specific (and strictly enforced) shape to them. The adjective must be a single word. We have to say "its" (i.e., of it), not the ungrammatical "it's"; we have to specify a property, and a literal value of it, and we must either give an exact value or else conclude with "or more" or "or less". If we create something with one of these properties: The basket is a large container in the Shop. The thimble is a small container in the Shop. The matchbox is a standard container in the Shop. then they will have the most moderate values they can have, that is, the basket will have carrying capacity 10 and the thimble 5 (and of course the matchbox 7). Both of the following tests will then fail: if the basket is huge ... if the basket is a small container ... because the basket is neither huge nor small, but somewhere in between. Sometimes the meaning of adjectives must depend on their context, as we see from the following example, where we assess heights in inches: A person has a number called height. Definition: A man is tall if his height is 72 or more. Definition: A woman is tall if her height is 68 or more. Inform then judges whether someone is or is not "tall" using different standards for men and for women, and In the Shop are a tall man and a tall woman. creates a man 72 inches tall and a woman 68 inches tall. 6.7. Comparatives The special definitions in the previous section have a further effect. When we define: Definition: A container is large if its carrying capacity is 10 or more. we not only say how to test if something is large (see if its capacity is at least 10) and how to create something large (give it a capacity of exactly 10), we also create a new form of comparison. Thus, if the basket is larger than the thimble ... if the thimble is not larger than the basket ... are both true. If we also define "huge" and "small", as in the previous section, we also get comparisons "huger than" and "smaller than". Note that "huger than" has exactly the same meaning as "larger than": we can use whichever wording seems more natural. (For bacilli, for instance, we would probably not say "huger than", even though the meaning would be unambiguous.) We can also compare two things to see if they share the same value of a property. For instance, to go back to the heights example, once we define "tall" and "short", we get that exactly one of the following will be true: if Adam is taller than Eve ... if Adam is the same height as Eve ... if Adam is shorter than Eve ... Though it will not always seem natural wording, we can use the comparison "the same P as" for any property P which has a value. Do we think "if the basket is the same carrying capacity as the thimble" is good English? Maybe, maybe not. But we are always at liberty to spell things out in full: if the carrying capacity of the basket is the carrying capacity of the thimble ... 6.8. Superlatives Lastly, if we define an adjective in this calibrating way, we also automatically benefit from the use of the superlative form. That is, if we define Definition: A container is large if its carrying capacity is 10 or more. Definition: A container is small if its carrying capacity is 5 or less. then we can talk about things like this: the largest container the smallest open container Though we should be careful, in the second case, because we might get nothing: maybe all the containers are closed at the moment this is used. And in general there might be several equally large largest containers, in which case we should not rely on getting any particular one of those rather than another. Note that Inform constructs comparatives and superlatives by a pretty simplistic system. If we want to use these forms for an adjective expressing the relatively large size of a room, we had better go with "roomy" (roomier, roomiest) - not "spacious" (spaciouser, spaciousest). 6.9. Which and who A description can not only talk about things in terms of themselves, but also in terms of their relationships to the rest of the world. For instance, an open container on the table a woman inside a lighted room an animal carried by a man a woman taller than Mark something worn by somebody are all valid descriptions. These are really abbreviations, having missed out the words "which is" or "who is", as appropriate: an open container which is on the table a woman who is inside a lighted room an animal which is carried by a man a woman who is taller than Mark something which is worn by somebody and indeed those are also valid descriptions. The other sentence verbs can all be used here, too. So for instance: a man who does not wear anything something which supports something And sometimes we should spell out "who is" regardless: a man who is not Sherlock Holmes Since these clauses can be attached to the end of any valid description, descriptions can grow longer still: something worn by a woman who is in a dark room Pedants who flinch when "which" is used to introduce a restrictive clause are welcome to use "that" instead. Example 75 (**): Versailles A mirror which will reflect some random object in the room. 6.10. Existence and there "There" is a curious word in English, which mostly refers to some place which is being talked about - but which can sometimes mean the whole world. In Ian Fleming's novel "From Russia With Love", a chapter narrating a committee meeting of SMERSH officers in Istanbul ends with one of the Russians saying: There is a man called Bond. What does this "there" mean? It really just means that Bond exists. In fact, he's watching the meeting through a concealed periscope, but the SMERSH general doesn't know that. All he is saying is that Bond is out there somewhere, and is not imaginary, or dead. Inform also allows "there is" (or "there are") to talk about what exists, or does not. This is especially useful if, for some reason, we don't want to give a name to something. For example: There is a door in the Summerhouse. Another reason might be that we want to create something but not put it anywhere. If Inform reads the sentence: There is a man called Bond. then it creates a man, gives him the name Bond, but places him initially off-stage - not in any room, that is, but available to be brought into play later on, like an actor who is not needed until Act II. "There" also provides a useful way to test what exists: if there is a woman in the Summerhouse, ... Or even: if there is a woman, ... which will be true if the model world contains even a single woman, on-stage or off. The alternative "there are" can also be used: if there are women in the Summerhouse, ... but note that this does not necessarily imply more than one woman is present, despite the plural. If we want that, we have to be more explicit: if there is more than one woman in the Summerhouse, ... or, of course, we needn't use "there is" at all: if more than one woman is in the Summerhouse, ... And we can also test non-existence: if there is nobody in the Summerhouse, ... if there is nothing on the mantelpiece, ... 6.11. A word about in What does "in" mean? It's worth just a brief diversion to cover this, because "in" has two subtly different meanings. Meaning 1. Usually, if X is "in" Y then this is because of containment. A croquet ball is "in" a croquet box, which is "in" the Summerhouse. This is the standard meaning, and is the one which happens if we write something like: The croquet ball is in the box. or if we ask a question like: if the croquet box is in the Summerhouse, ... This kind of "in" talks only about direct containment. If we ask if the croquet ball is in the Summerhouse, ... then the answer is that it isn't - it is in the box which is itself in the Summerhouse, but that's not the same thing. This is almost always the meaning of "in" that we intend. This is only one of a number of relationships between objects - there are also "part of", "on", "worn by" and "carried by", for example. If we have The bird feed is on the sundial. ...then "if the bird feed is in the sundial" won't be true: the relationship here is one called support (being on top of, in effect), not containment. But there's no confusion because "on" and "in" are different words, so it's no problem that they have different meanings. Meaning 2. Much less common. If X is "in" Y and Y is a region, then the meaning is slightly different. Suppose the Garden Area is a region, and contains several rooms - the Croquet Lawn, the Terrace and so on. Then if the croquet box is in the Garden Area, ... if the bird feed is in the Garden Area, ... if the Terrace is in the Garden Area, ... are all true. This seems very natural, but in fact is quite different from the first meaning of "in". It allows rooms (and even other regions) to be "in" a region, and it allows indirect containment. How Inform decides. So which meaning does Inform use, and when? Since these two meanings are so different, it clearly matters. The answer is that meaning 1 is always the meaning of "X is in Y" unless Y is explicitly the name of a region. Thus: if the croquet box is in the Garden Area, ... is meaning 2, because "Garden Area" is the name of a region. That seems fair enough, but in later chapters, we'll see that values are sometimes given names (becoming "variables", or values "that vary"). Suppose "mystery value" is a name for a value which is an object, but which has different identities at different times. Then Inform reads if the croquet box is in the mystery value, ... as meaning 1, because whatever "mystery value" is, it isn't explicitly a region name, even if from time to time it might happen to be equal to a region. That sometimes makes meaning 2 difficult to express. If we ever need it, and this is fairly rare, we can write it like so: if the croquet box is regionally in the mystery value, ... because "regionally in" is always meaning 2 of "in". 6.12. A word about nothing Like "in", "nothing" has two slightly different meanings, though here there's much less potential for confusion. Meaning 1. "Nothing" as "no thing". This is the meaning in sentences like: Definition: a container is bare if nothing is in it. And similar for conditions like "if the box contains nothing". It's a word which describes the absence of things: it says that, though there might have been many possible items here, it turned out that there were none. Meaning 2. "Nothing" as a value. This is much less commonly seen, but sometimes Inform stores a value such as a property (or a variable, of which more in later chapters) which always has to be an object. In some circumstances, "nothing" is then a special value meaning that this is not set at present. For instance, Definition: a container is impossible if its matching key is nothing. The "matching key" property of a container is always an object, but is allowed to be "nothing" when there isn't a matching key anywhere. (If such a container is locked, nobody will ever be able to unlock it.) How Inform decides. So which meaning does Inform use, and when? The answer is that it depends on the relationship being talked about. When this is "is", values are being compared and we are using meaning 2. But when it is any other relationship, like "is in" - which talks about containment - then we are using meaning 1. 6.13. To be able to see and touch Two of the adjectives built into Inform are: "visible" - the player can see this "touchable" - the player can touch this So we can write descriptions such as "someone visible" or "a touchable container". We also have adjectives "invisible" and "untouchable", as might be expected. The visibility adjectives are particularly useful because the following is likely to go wrong: if Helen is in a dark room, ... This tests whether the room is dark, of itself; Helen may in fact be able to see by means of a torch, but the room is still "dark". We can also talk about what other people can see and touch: something able to be seen by Helen something which can be seen by Helen are synonymous. Similarly for touch; and we can write such conditions as if Helen is unable to see Agamemnon, ... if Cressida can see Troilus, ... Note that it is essential to establish who does the seeing and touching: so "something which can be seen" will not be allowed, whereas "something which can be seen by Helen" will. In fact, inside Inform the adjective "invisible" (for instance) has the following straightforward definition: Definition: Something is invisible if the player cannot see it. The exact definitions of visibility and touchability are complicated, because there are so many ways in which vision and touch can be obstructed, but the gist is that they behave as one would expect. Note that in darkness, nothing is visible, and that nobody can see from one room to another. In general anything invisible is also untouchable, but there are a few exceptions to do with being in the dark. Lastly, the player's own body (usually called "yourself" during play) is both visible (in light) and touchable. Example 76 (***): Lean and Hungry A thief who will identify and take any valuable thing lying around that he is able to touch. 6.14. Adjacent rooms and routes through the map Another useful adjective built into Inform is "adjacent". Two rooms are said to be adjacent if there is a map connection between them which does not pass through some barrier such as a door. This is easily tested: if the Hallway is adjacent to the Study ... We usually want to know about the places adjacent to the current scene of the action, so that is what the adjective "adjacent" means when applied to rooms. For instance: if somebody is in an adjacent room, ... As with the case of "visible", the adjective is a cut-down version of the more general relationship. This often happens: "worn" and "carried", for instance, imply "by the player" unless something else is specified. If we want to ask a more direct question, we can obtain specific map connections as follows. (Recall that every map connection leads either to a door, to a room, or to nothing.) If we know which direction we want to look in, then the easiest thing is to use its relation - every direction in the map, say "north", has its own relation, say "mapped north of". So: if the Ballroom is mapped north of the Hallway, ... Alternatively, and particularly if the direction is not a constant,

room (direction) from/of (room) ... room
This phrase produces the room which the given map direction leads to, or the special value "nothing" if it leads nowhere or to a door. Examples: say "You look north into [the room north from the Garden]." if the room north from the Garden is nothing, say "The grass leads nowhere."

door (direction) from/of (room) ... door
This phrase produces the door which the given map direction leads to, or the special value "nothing" if it leads nowhere or to a room. Examples: let the barrier be the door north from the Garden; if the barrier is a door, say "Well, [the barrier] is in the way.";

room-or-door (direction) from/of (room) ... object
This phrase produces the object which the given map direction leads to, which will always be either a room, a door or the special value "nothing". The phrase is used mainly by the Standard Rules, for technical reasons, and usually it's better to use "room ... from ..." or "door ... from ..." instead.
The map can be a great sprawling mass of rooms and doors connected together, and it can be quite hard to find a way through it one step at a time.

best route from (object) to (object) ... object
This phrase produces a direction to take in order to get from A to B by the shortest number of movements between rooms, or produces "nothing" if there is no way through at all. Example: The description of the brass compass is "The dial points quiveringly to [best route from the location to the Lodestone Room]." Best routes are ordinarily forbidden to go through doors, but if the suffix "using doors" is added as an option then any open or openable and unlocked door may be used on the way; and if "using even locked doors" is given, then any door at all will do. Since magnetism is no respecter of property, that seems right here: The description of the brass compass is "The dial points quiveringly to [best route from the location to the Lodestone Room, using even locked doors]."
In practice this simple approach sometimes produces impossible journeys, rather the way Google Maps directions from New York to London would recommend driving down to the docks and then swimming. A more careful approach is to use:

best route from (object) to (object) through (description of objects) ... object
This phrase produces a direction to take in order to get from A to B by the shortest number of movements between rooms which match the given description, or produces "nothing" if there is no way through at all. Example: best route from the Drawbridge to the Keep through visited rooms The condition - in this case, that "visited rooms" must be used - also applies to both ends of the journey, so if either Drawbridge or Keep are unvisited then this is "nothing". (Similarly, saying something like "...through containers" would mean there is never a route.)
Lastly, the following phrases can find out how long the journey would be. (They are quite a bit faster than using the "best route..." phrases repeatedly and counting.)

number of moves from (object) to (object) ... number
This phrase produces the number of map connections which must be followed in order to get from A to B by the shortest number of movements between rooms. If A and B are the same, the answer is 0; if there is no route at all, the answer is -1. Example: The description of the proximity gadget is "You are now [number of moves from the location to the Sundial] moves from the Sundial.";

number of moves from (object) to (object) through (description of objects) ... number
This phrase produces the number of map connections which must be followed in order to get from A to B by the shortest number of movements between rooms matching the given description. If A and B are the same, the answer is 0; if there is no route at all, or if either A or B fail to match the description themselves, the answer is -1.
Route-finding makes it possible to write quite sophisticated conditions concisely. But these sometimes run slowly, because they call for large amounts of computation. How rapidly Inform can find routes depends on which of two methods it uses. Both have advantages - one is fast but needs large amounts of memory, the other is slow but economical. We can choose between them with one of these two use options: Use fast route-finding. Use slow route-finding. If neither is specified, "fast" is used where the project uses the Glulx virtual machine (see the Settings panel), and "slow" on the Z-machine, where memory is tighter. Fast route-finding is ideally suited to situations where dozens of characters are constantly route-finding through the map as they meander around in a landscape. (- See Indirect relations for route-finding through a relation rather than the map.) Example 77 (*): Mistress of Animals A person who moves randomly between rooms of the map. Example 78 (*): All Roads Lead to Mars Layout where the player is allowed to wander any direction he likes, and the map will arrange itself in order so that he finds the correct "next" location. Example 79 (**): Hotel Stechelberg Signposts such as those provided on hiking paths in the Swiss Alps, which show the correct direction and hiking time to all other locations. Example 80 (***): A View of Green Hills A LOOK [direction] command which allows the player to see descriptions of the nearby landscape. Example 81 (***): Unblinking Finding a best route through light-filled rooms only, leaving aside any that might be dark. 6.15. All, each and every When testing conditions, we normally talk only about specific things, or else ask if a particular circumstance happens: if the oaken door is open if a woman is carrying an animal But we can also use "all", "each" or "every" to check the whole range: if each door is open if anyone is carrying all of the animals if everybody is in the Dining Room Inform allows other English "determiners" (as they are sometimes called), as well: if some of the doors are open if most of the doors are open if almost all of the doors are open are true if at least one case is true, if a majority (any number greater than one half) or at least 80 per cent of the possible cases are true, respectively. And we can also use "none" and "no". These three are all ways to say the same thing: if no door is open if all of the doors are not open if none of the doors is open though it may be clearer style to find a positive way of putting things: if all of the doors are closed All, each and every can be applied to values, too - but only in some cases. For example, suppose we write: Colour is a kind of value. The colours are red, orange, yellow, green, blue, indigo and violet. A colour can be found or unfound. And suppose that, during play, we assign the "found" property to any colour which the player notices on a wall. We might then want to write conditions like so: if every colour is found if most of the colours are found if any colour is found But we always have to bear in mind that Inform might have no reasonable way to decide these questions. It will refuse to allow these, for example: if every number is positive if any text is palindromic (even supposing the adjective "palindromic" has been defined) - there are practically infinitely many possible numbers and texts, so the search cannot sensibly be done. Example 82 (****): Revenge of the Fussy Table A small game about resentful furniture and inconvenient objects. 6.16. Counting while comparing Lastly we can also ask for a more specific number of possibilities, like so: if two women are carrying animals if at most three doors are open if fewer than 10 portable containers are closed if all but two of the devices are switched on if there are more than six locked doors Likewise for "less than", "at least", "all except". Something to watch out for is that if two doors are open will be found true if there are (say) three open doors: after all, if three doors are open, then certainly two doors are. So this is not quite counting. We can be more precise by writing if exactly two doors are open The "all but" counts - say, "if all but two doors are open" - are exact: if, in fact, all of the doors are open then this will be found false. We can often use these counting forms with values, too. As with the use of "all", this is allowed only if the kind of value is one which can reasonably be searched through. For example: if more than three scenes are happening if there are more than two non-recurring scenes are allowed because the built-in kind of value "scene" (of which much more later on) has only a small number of possible values. Lastly, note that the "the" in text like "two of the doors" matters: without it, the phrase will not be recognised as a requirement on the number. (This is to make sure that names of things like "two of hearts" are not misinterpreted.) Example 83 (**): Yolk of Gold Set of drawers where the item the player seeks is always in the last drawer he opens, regardless of the order of opening. 6.17. Review of Chapter 6: Descriptions 1. The lexicon. Inform's lexicon is not just a figure of speech: Inform actually does maintain an alphabetical list of nouns and adjectives which can be used in descriptions, and that lexicon can be browsed in a project's Index. To summarise. Nouns are straightforward: they refer to specific things ("wine cask") or specific kinds (even "something", which refers to "thing") or specific kinds of value ("number"). Adjectives, however, come from several sources: (a) From either/or properties. For instance, "open" and "closed", which are antonyms: what is not open is closed, and vice versa. (b) When we create a new kind of value, and allow it to be a property of a given kind, we also create new adjectives: Colour is a kind of value. The colours are red, blue and green. A building block is a kind of thing. A building block has a colour. We can now use the adjective "green" (for instance) in descriptions: Instead of taking a green building block, say "For some reason you have an aversion to the colour green." And similarly when we use the more convenient form for single things, such as the cask in this example: The cask is either customs sealed, liable to tax or stolen goods. (c) From direct definitions, such as the adjective "occupied" created by: Definition: a supporter is occupied if something is on it. (d) We can define adjectives that describe properties falling within a certain range, like so: Definition: A container is large if its carrying capacity is 10 or more. Definition: A container is standard if its carrying capacity is 7. Definition: A container is small if its carrying capacity is 5 or less. Then we can make comparisons and look for the most extreme examples of things: if the basket is larger than the thimble ... if the thimble is not larger than the basket ... if the bag is the same carrying capacity as the basket ... if the thimble is smaller than the basket ... if the thimble is the largest visible container ... let the current container be the smallest container carried by the player. 2. Descriptions. As we have seen, we are also allowed to use more complicated descriptions of things: an open container on the table a woman inside a lighted room something which is worn by somebody a man who does not wear anything something which supports something For the time being, this ability is of only limited use, but we will see shortly that it will let us write instructions for what the game should do under complex circumstances; e.g., Before taking something which is in a closed transparent container: ... Instead of wearing something which offends the player: ... We are allowed also to count the number of objects that correspond to a description, as in the number of women who are concealing weapons and we may ask how many of a category correspond to a description: if each door is open if anyone is carrying all of the animals if everybody is in the Dining Room if some of the doors are open if most of the doors are open (i.e., more than half) if almost all of the doors are open (i.e., 80 percent or more) if two women are carrying animals if at most three doors are open if fewer than 10 portable containers are closed if all but two of the devices are switched on As we have seen, if two doors are open is equivalent to if at least two doors are open but we may insist on exactitude with if exactly two doors are open 3. Seeing and touching. We may also talk about what can be seen and touched by the player (or by other characters or even other objects): if the rubber chicken is visible means the same thing as if the player can see the rubber chicken but we the player need not be the focus of the question: if the video camera can see the felon if the pool is able to be touched by the live wire The chapter on Advanced Actions discusses how we may change Inform's definition of what can be seen or touched, if that becomes necessary; the chapter on Relations shows how to create other "is able" conditions. 4. Routes through the map. "An adjacent room" is a room which can be reached in a single move from the player's current location, via a path that does not pass through any doors (open or closed). a room adjacent to the Factory Floor applies the same criterion to the Factory rather than the current location. We may also talk about the room east from the Factory Floor for example, or more complicatedly, best route from the location to the Lodestone Room best route from the location to the Lodestone Room, using doors best route from the location to the Lodestone Room, using even locked doors where the best route will be the direction to travel first when moving towards the Lodestone Room, and the optional "using doors" and "using even locked doors" indicate whether these paths should be included. Moreover, we can plot a course only through rooms that meet a certain criterion, as in best route from the Drawbridge to the Keep through visited rooms best route from the Drawbridge to the Keep through lighted rooms, using doors This can be especially useful in the case where we want to find a path for the player but only allow him to travel through rooms he has already seen once; but any adjective that applies to a room may be used in place of "visited" or "lighted" in these examples. We may find the lengths of these journeys with phrases like: number of moves from the location to the Sundial number of moves from the location to the Sundial, using doors number of moves from the location to the Sundial through visited rooms, using even locked doors Chapter 7: Basic Actions 7.1. Actions "Actions" are what we get if we try to break down a narrative into its irreducible parts. We might casually say that we are "going shopping", but this involves many smaller steps: going north, going east, entering the shop, examining a loaf of bread, taking it, giving money to the baker, and so on. An action is an impulse to do something. This may or may not be a reasonable aspiration, and may or may not be achieved. The player's exploration of an interactive fiction is made by a sequence of actions, so much of the designing process comes down to responding to these actions. We write actions using present participles. For instance, if the player types "take napkin" or "get the napkin" or something similar then the resulting action would be written as: taking the napkin The details of what words the player actually typed are unimportant to us: we deal only in actions. Every action ends in success or failure. In this context, success means only that the player's intention has been fulfilled. If the player sets out to take the napkin, but finds a million-pound banknote in its folds instead, the action will be deemed to be a failure. (Testing command) The testing command ACTIONS causes Inform to log every action as it happens, and what its outcome is. (ACTIONS OFF turns this off again.) For instance: >s [going south] Security Vault You can see a metal door here. [going south - succeeded] >close door [closing metal door] You close the metal door. [closing metal door - succeeded] >take door [taking metal door] That's fixed in place. [taking metal door - failed the can't take what's fixed in place rule] A good way to get a sense of the constant flow of actions is to use this command and then wander around an existing work, trying things out. ACTIONS can also give an insight into the web of rules governing play: there are nine or ten different ways an attempt to take something can fail, for instance. 7.2. Instead rules An action is ordinarily handled by running it through Inform's extensive rulebooks of what might be called normal behaviour. An action such as "taking the napkin", for instance, will be run through numerous checks to see if it is physically reasonable, and then provided all is well, the napkin will be moved into the possession of the player. Instead, though, we can bypass the rules to do with an action and do something else: Instead of eating the napkin: say "Why not wait for the actual dinner to arrive?" This is an example of a "rule": a set of circumstances followed by a list of instructions. When those circumstances apply, the instructions are carried out. In the case of an "instead" rule, after this is done the action is immediately ended (and counts as a failure, since the original intention has been thwarted). A friendly alternative can be used when there is only a single instruction, as here: in such rules the colon can be replaced with a comma. Thus: Instead of eating the napkin, say "Why not wait for the actual dinner to arrive?" Example 84 (*): Grilling A grill, from which the player is not allowed to take anything lest he burn himself. Example 85 (*): Bad Hair Day Change the player's appearance in response to EXAMINE ME. 7.3. Before rules Despite what was said in the previous section, instead rules do not quite bypass all of the usual rules. Inform knows that certain actions require light: for instance, examining the napkin; looking; looking under the dining table and if it is dark then none of these actions will be allowed, and any instead rules about them will not even be reached. Similarly, Inform knows that most actions require physical access to their objects: so "taking the napkin" would be blocked if the napkin were, say, inside a closed glass bottle, whereas "examining the napkin" would not. So an instead rule can only take effect if the action has already passed these basic reasonability tests. "Before" rules genuinely precede checking of any kind. They also differ from instead rules in that they do not automatically stop the action in its tracks. Rather, they are provided as an opportunity to ensure that something else is done first. For example: Before taking the napkin, say "(first unfolding its delicate origami swan)". whence >GET NAPKIN (first unfolding its delicate origami swan) Taken. We have seen that instead rules automatically stop actions, whereas before rules automatically allow them to continue. We sometimes want to change this. The magic word "instead" can therefore be tacked on to any instruction in a before rule, and will have the effect of immediately stopping the action at that instruction. Thus the following two rules are (almost) equivalent: Before taking the key, instead say "It seems to be soldered to the keyhole." Instead of taking the key, say "It seems to be soldered to the keyhole." It is also possible to be explicit about stopping the action:

stop the action
This phrase stops the current rule, stops the rulebook being worked through, and finally stops the action being processed. Example: Before taking the key: say "It seems to be soldered to the keyhole."; stop the action.
Finally, we can prevent Inform from stopping the action when it otherwise might:

continue the action
This phrase ends the current rule, but in a way which keeps its rulebook going, so that the action being processed will carry on rather than being stopped. Example: Instead of taking the napkin: say "(first unfolding its delicate origami swan)[command clarification break]"; continue the action. An "instead" rule ordinarily stops the action when it finishes, so the "continue the action" is needed to make things carry on. (This rule would have been better written as a "before" rule, in fact, but it shows the idea.)
As a general principle, it is good style to use instead rules whenever blocking actions, and before rules only when it is genuinely necessary to do something first but then to continue: in fact, it is good style to use "stop the action" or "continue the action" as little as possible. Example 86 (***): Democratic Process Make PUT and INSERT commands automatically take objects if the player is not holding them. Example 87 (****): Sand Extend PUT and INSERT handling to cases where multiple objects are intended at once. 7.4. Try and try silently Chapter 2 noted that surveys of Inform source text showed that the three most popular phrases used by authors are "say", "if" and "now". The fourth most popular is "try", which allows us to trigger off actions ourselves, rather than waiting for the player to type something which generates them. Thus:

try (action)
This phrase makes the action, which has to be named literally, take effect now. Example: Instead of entering the trapdoor, try going up. It's as if the player had typed GO UP as a command. Note that the action has to be specific: try eating something; is not allowed, since it doesn't say exactly what is to be eaten.
The word "try" is intended to make clear that there is no guarantee of success. For example: Before locking the front door, try closing the front door. could go wrong in any number of ways - perhaps the door is closed already, perhaps it is not openable, perhaps somebody has wedged it open. It would be safer to write: Before locking the front door: try closing the front door; if the front door is open, stop the action. There's no need to say anything if closing didn't work, because the closing action will have done that already. A neater approach still is to use:

silently try (stored action)
or: try silently (stored action)
This phrase makes the action, which has to be named literally, take effect now, under the "silent" convention which means that routine messages aren't printed. Example: try silently taking the napkin; Silence is maintained only if this new action, the taking of the napkin, is successful (so if the napkin is successfully taken, the text "Taken." will not appear): if the action should fail, a suitable objection will be voiced as usual.
So now we have: Before locking the front door: try silently closing the front door; if the front door is open, stop the action. And this is neater because it won't produce a pointless "You close the front door." message. (See Stored actions for how to store up actions as values and try those, too, so that isn't necessary to name the action as literally as in the examples above.) Example 88 (*): Fine Laid Making writing that can be separately examined from the paper on which it appears, but which directs all other actions to the paper. Example 89 (*): Hayseed A refinement of our staircase kind which can be climbed. 7.5. After rules There is pleasantly little to be said about "after" rules. If an action has survived all the rules in its way, and has actually succeeded, then we need to give the player a response which acknowledges this. Inform's normal rules will be sufficient to say something undramatic: for instance, if "taking the napkin" has succeeded then it will reply "Taken." to the player. An after rule is an opportunity to say something more interesting: After taking the diamonds, say "Taken!" (Well, slightly more interesting.) After rules automatically end the action (as a success), which is what we would want in the above case. Allowing it to continue would simply result in "Taken." being printed as well. However, should we really need to do something and then carry on: After taking the diamonds: say "(Mr Beebe looks up sharply.) "; continue the action. Example 90 (*): Morning After When the player picks something up which he hasn't already examined, the object is described. 7.6. Reading and talking A few actions apply not to items alone, but also involve what might be called conversation. The first is the one used for looking things up in books (which is conversation of a kind, even if the author is not present): "consulting ... about ...". For example, In the Grove is a book of sybilline verses. After consulting the book about "grove", say "The Grove is a sacred yadda, yadda. There's a tree, that sort of thing. Wisdom." After consulting the book about "future events", say "It's a bit, what's the word? Delphic." Note that what follows "about" here is a piece of text in double-quotes, and not the name of something. It can be almost any text at all, and in fact we shall later see (in the chapter on "Understanding") that we can match complicated patterns of words, too. Similar actions are used for conversing with people: After asking the Sybil about "verses", say "She blushes." After telling the Sybil about "persians", say "She nods gravely." After answering the Sybil that "I am mad", say "She sighs." These would be produced by commands like "ask sybil about verses", "tell sybil about persians" and "answer i am mad". Answering is very seldom used and can be forgotten about, but the distinction between asking and telling is often worth preserving, which is why there are two different actions for these. If you would prefer to make "tell sybil about X" do the same as "ask sybil about X", the following rule would serve: Instead of telling the Sybil about something, try asking the Sybil about it. Games with a lot of conversation often involve great heaps of rules like the ones above, which can be repetitious to type out. We shall also later see (in the chapter on "Tables") that we can tabulate questions and answers in a much more concise way, if we prefer. (See Topic columns for table-based ways to store and retrieve conversation.) Example 91 (*): Sybil 1 Direct all ASK, TELL, and ANSWER commands to ASK, and accept multiple words for certain cases. Example 92 (*): Lucy Redirecting a question about one topic to ask about another. Example 93 (**): Sybil 2 Making the character understand YES, SAY YES TO CHARACTER, TELL CHARACTER YES, ANSWER YES, and CHARACTER, YES. Example 94 (***): Costa Rican Ornithology A fully-implemented book, answering questions from a table of data, and responding to failed consultation with a custom message such as "You flip through the Guide to Central American Birds, but find no reference to penguins." 7.7. The other four senses The five senses are all simulated with actions. Sight is so informative that it is handled by a whole range of actions: "looking", which describes the general scene; "examining something", which takes a closer look at a specific thing; "looking under something", and so on. The other senses have one action each: "listening to something", "touching something", "tasting something" and "smelling something". It makes no sense to touch or taste the general scene, but listening and smelling are a different matter: we often just listen, without listening to anything specific. If the player types the command "listen", Inform understands that as listening to the current location: similarly for the bare command "smell". Thus: Instead of listening to the Seashore, say "The song of gulls." Instead of smelling the Cave, say "Salt and old seaweed." (Note the difference between this and saying: Instead of listening in the Seashore, say "The song of gulls." With this rule, even typing "listen to shell" when at the Seashore would result in the song of gulls: fine if the gulls drown all else out, but otherwise incongruous.) Example 95 (***): The Art of Noise Things are all assigned their own noise (or silence). Listening to the room in general reports on all the things that are currently audible. 7.8. Rules applying to more than one action A description can include more than one choice of action. For instance: examining or searching the desk matches either of "examining the desk" or "searching the desk". We can have more than two actions, of course: examining, looking under or searching the desk The actions combined like this need to be compatible with each other, at least a little. For instance, this will generate a problem message: waiting or searching the desk because it makes no sense to "wait the desk". On the other hand, this is fine: waiting or searching The general rule is that if we specify one or more objects ("the desk" in the above example), then each of the actions we quote must take at least that many objects. For example, the following saves us writing the same basic rule three times over: Instead of examining, looking under or searching the desk: say "There's no use poking around in that old desk." 7.9. All actions and exceptional actions The special description "doing something" (or "doing anything") matches any action, and "doing something to ..." also allows the noun to be specified. For instance, the following puts its object out of bounds: Instead of doing something to the cucumber sandwich, say "Lady Bracknell stares disapprovingly down her pince-nez at you, in a way which no amount of hunger or curiosity could overcome." We sometimes need to be a little careful here: "waiting" qualifies as "doing something", but not as "doing something to something", because there is no object. "Putting the handbag on the cucumber sandwich" would also not qualify as "doing something to the cucumber sandwich" - only to the handbag. More often, we would like to restrict the range of allowable actions to a select few. For instance: Instead of doing something other than looking, examining or waiting: say "You must learn patience." (Or we can write "except" instead of "other than".) Or we might have an object, too: Instead of doing something other than examining, taking or dropping with the dagger: say "Don't fool around with that dagger. It's exceedingly sharp." Note the "with", which was optional, but makes it clearer that the rule applies only to actions on the dagger. Example 96 (*): Zodiac Several variations on "doing something other than...", demonstrating different degrees of restriction. 7.10. The noun and the second noun Once we begin applying rules to actions which are not entirely known in advance, we have a problem: there's no way to find out what specifically is happening. Consider the following: Instead of examining something, say "It is none of your concern!" This is fine as far as it goes, but clumsy. What if the player had examined a human being? Then "it" would be inappropriate. A better approach would be this: Instead of examining something, say "[The noun] is none of your concern!" The "noun" and, when necessary, the "second noun" are values which can be used in any rule about actions, and it follows that they can also be substituted into text, as this example demonstrates. Results might include: Lady Bracknell is none of your concern! The silver cigarette case is none of your concern! This seems a good moment to mention that if you use "The" in a substitution, then a capitalised "The" will be used so long as this is grammatically correct (Lady Bracknell, as a proper noun, takes no article); "the" becomes a lower-case "the" along the same lines; and "a" a lower-case indefinite article. Instead of examining something in the Drawing Room, say "Under Lady Bracknell's eye, you feel constrained. Besides, it is only [a noun]." Example 97 (*): Ming Vase ATTACK or DROP break and remove fragile items from play. 7.11. In rooms and regions Three elaborations of action descriptions increase the range of possibilities further. Instead of taking something in the Supernatural Void, say "In this peculiar mist you feel unable to grasp anything." Like the objects to which the action applies, this location - the "in" clause - can take any description, not just an explicit place like "Supernatural Void": Instead of listening in a dead end, say "You strain to hear further clues as to the course of the underground river, but to no avail." But we often want a rule to apply in any of a set of rooms: and where, unlike the "dead end" example above, the rooms have nothing much in common except where they happen to lie on a map. For instance, we might want a rule to apply only inside a given building, or a garden consisting of five miscellaneous rooms. If so, we can create a "region" as a convenient way to refer to that group of rooms: The Arboretum is east of the Botanical Gardens. Northwest of the Gardens is the Tropical Greenhouse. The Public Area is a region. The Arboretum and Gardens are in the Public Area. Instead of eating in the Public Area, say "The curators of the Gardens are ever among you, eagle-eyed and generally cussed." 7.12. In the presence of, and when Relative location can also be important: relative to other people, that is - Instead of eating something in the presence of Lady Bracknell, say "Lady Bracknell disapproves thoroughly of gentlemen who snack between meals, and there are few disapprovals in this world quite so thorough as Lady Bracknell's." As might be guessed, this applies when the action takes place in the same location as the person named: and of course that person can also be described more vaguely ("... in the presence of a woman", say), and can just as easily be an inanimate thing ("... in the presence of the radio set"). Lady Bracknell is a pushover compared to some matriarchs: Instead of doing something other than looking, examining or waiting in the presence of the Queen: say "I'm afraid they take what you might call a zero tolerance approach to breaches of court etiquette here."; end the story saying "You have been summarily beheaded". The last of the optional clauses we can tack on to the description of an action is the most general of all. We can add "when" and then any condition at all, as in: Instead of eating something when the radio set is switched on, say "Something about the howling short-wave static puts you right off luncheon." This supposes that the radio is so loud that it can be heard from any room: we could muffle it so that it's only audible from the room it is in like so: Instead of eating something in the presence of the radio set when the radio set is switched on, say "Something about the howling short-wave static puts you right off luncheon." Example 98 (*): Beachfront An item that the player can't interact with until he has found it by searching the scenery. Example 99 (**): Today Tomorrow A few notes on "In the presence of" and how it interacts with concealed objects. 7.13. Going from, going to Going is an action defined like any other: it is the one which happens when the player tries to go from one location to another. But it is unlike other actions because it happens in two locations, not just one, and has other complications such as vehicles and doors to contend with. To make it easier to write legible and flexible rules, "going" is allowed to be described in a number of special ways not open to other actions, as demonstrated by the following example game: "Going Going" The Catalogue Room is east of the Front Stacks. South of the Catalogue Room is the Musicology Section. Instead of going nowhere from the Front Stacks, say "Bookcases obstruct almost all passages out of here." Instead of going nowhere, say "You really can't wander around at random in the Library." Before going to the Catalogue Room, say "You emerge back into the Catalogue Room." Note that "going nowhere" means trying a map connection which is blank, and if no rules intervene then "You can't go that way" is normally printed. Unless "nowhere" is specified, descriptions of going apply only when there is a map connection. So "going from the Musicology Section" would not match if the player were trying to go east from there, since there is no map connection to the east. Similarly, "going somewhere" excludes blank connections. The places gone "from" or "to" can be specific named regions instead of rooms. This is convenient when there are several different ways into or out of an area of map but a common rule needs to apply to all: so, for example, Before going from the Cultivated Land to the Wilderness, ... Before going nowhere from the Wilderness, say "Tangled brush forces you back." Note that it must be "going nowhere from the Wilderness", not "...in the Wilderness". (Note also the caveat that the regions must be named: "going from a region", or something similarly nonspecific, will not work.) An important point about "going... from" is that, as mentioned in general terms above, it requires that there is actually a map connection that way: whereas "going... in" does not. Suppose there is no map connection north from the Wilderness. Then: Instead of going north from the Wilderness, say "You'll never read this." Instead of going north in the Wilderness, say "Oh, it's too cold." The first of these never happens, because it is logically impossible to go north from the Wilderness: but the second does happen. (Technically, this is because "going north" is the action, and "in the Wilderness" a separate condition tacked onto the rule.) This distinction is often useful - it allows us to write rules which apply only to feasible movements. This may be a good place to mention a small restriction on the ways we can specify an action for a rule to apply to, and how it can be overcome. The restriction is that the action should only involve constant quantities, so that the following does not work: The Dome is a room. The Hutch is north of the Dome. The rabbit is in the Hutch. Before going to the location of the rabbit, say "You pick up a scent!" because "the location of the rabbit" is a quantity which changes in play (the player can pick up the rabbit and take him to the Dome, for instance). However, we can get around this restriction by defining a suitable adjective, like so: The Dome is a room. The Hutch is north of the Dome. The rabbit is in the Hutch. Definition: a room is rabbit-infested if it is the location of the rabbit. Before going to a rabbit-infested room, say "You pick up a scent!" Example 100 (*): Veronica An effect that occurs only when the player leaves a region entirely. Example 101 (**): A&E Using regions to block access to an entire area when the player does not carry a pass, regardless of which entrance he uses. Example 102 (***): Polarity A "go back" command that keeps track of the direction from which the player came, and sends him back. Example 103 (***): Bumping into Walls Offering the player a list of valid directions if he tries to go in a direction that leads nowhere. 7.14. Going by, going through, going with Adding to the previous example game, we apply rules which depend on travelling by a particular vehicle: The book trolley is in the Musicology Section. "The book trolley, a sort of motorised tractor for trundling around through the stacks, is parked here." The trolley is a vehicle. Instead of going nowhere by the trolley, say "Don't go crashing the trolley into walls." Instead of going to the Front Stacks by the trolley, say "The Front Stacks are far too confined for the trolley to manoeuvre into them." And, lastly, rules which apply to movements through particular doors: The green baize door is east of the Catalogue Room and west of the Clerk's Office. The green baize door is an open door. Before going through the green baize door, say "Through you go..." After going through the green baize door: try looking; say "...and here you are." (Note that these apply whether the action is "going east" or "entering the green baize door", each having the same effect.) The last rule is worth a second look: the normal way that a "going" action is reported is to produce the room description of the new location. So if an "after" rule stops the action before we get to reporting, we have to produce any room description by hand (hence the "try looking" to cause the looking action). Alternatively, we could simply say something and let the normal course of events take place: After going through the green baize door: say "...and here you are:"; continue the action. Finally, going is an action which can also happen while the player is pushing something from one room to another, and we can describe this like so: Instead of going from the Office with the trolley, say "But it looks perfectly placed here. Why push any further?" "Going" is not the only action which moves the player. Another is "exiting", an action which moves the player out of whatever he/she is currently in or on. This action is often caused by the player typing just OUT or GET DOWN, and there's no noun as such. But Inform allows the syntax "exiting from" to make it easier to write rules about the exiting of particular containers or supporters: After exiting from the Mini Cooper: say "You painstakingly unpack your limbs from the tiny car." Example 104 (*): Mattress King Adding extra phrasing to the action to PUSH something in a direction. Example 105 (*): No Relation A car which must be turned on before it can be driven, and can only go to roads. Example 106 (**): One Short Plank A plank bridge which breaks if the player is carrying something when he goes across it. Pushing anything over the bridge is forbidden outright. Example 107 (***): Provenance Unknown Allowing something like PUSH TELEVISION EAST to push the cart on which the television rests. Example 108 (***): Zorb Replacing the message the player receives when attempting to push something that isn't pushable, and also to remove the restriction that objects cannot be pushed up or down. 7.15. Kinds of action Especially when people need to react to events going on around them, it is helpful to be able to categorise actions into whole areas of behaviour. For instance: Kissing Mr Carr is unmaidenly behaviour. Doing something to the painting is unmaidenly behaviour. Instead of unmaidenly behaviour in the Inn, say "How unmaidenly!" Here a new kind of action called "unmaidenly behaviour" has been created and then used in the description of an instead rule. The convenience of this approach is that when further actions suddenly occur to us as also being unmaidenly - say, attacking Mr Carr - we only need to add a single line: Attacking Mr Carr is unmaidenly behaviour. And this will automatically be reflected in any rules which concern the consequences of failing to be ladylike. (Note that we were only allowed to say that "Kissing Mr Carr is unmaidenly behaviour." because Inform already knew from earlier sentences - see the example below - that Mr Carr was a person, and therefore that "kissing Mr Carr" made sense as a description of an action.) Example 109 (*): Dearth and the Maiden Our heroine, fallen among gentleman highwaymen, is restrained by her own modesty and seemliness. Example 110 (***): Mimicry People who must be greeted before conversation can begin. 7.16. Repeated actions We come at last to the final thing which can be specified about an action, and appropriately enough it must be specified with the final words of the description. This is the way to talk about repeated activity: Instead of examining the tapestry for the third time, say "All right, so it's a masterpiece, but is this really the time to make a detailed study?" Instead of examining the urn at least twice, say "It's an urn. What do you want from me?" Instead of going nowhere for the 20th time, say "Do stop walking into walls, there's a good fellow." Note that we are allowed to spell out numbers up to twelve in English words, but beyond that must use digits (thus "twelfth" is allowed but not "thirteenth": "13th" should be used instead). The following example is instructive: Instead of taking something for the fourth time, say "No. I'm capricious." This means that it is the fourth time a "taking..." action has been tried, and does not mean that the same item was taken each time. Also, note that we are counting the number of times the action has been tried, not the number of times it succeeded. Example 111 (*): Y ask Y? Noticing when the player seems to be at a loss, and recommending the use of hints. Example 112 (****): A Day For Fresh Sushi A complete story by Emily Short, called "A Day for Fresh Sushi", rewritten using Inform 7. Noteworthy is the snarky commenter who remarks on everything the player does, but only the first time each action is performed. 7.17. Actions on consecutive turns We can also reckon the number of consecutive turns on which an action has been repeated, by talking about "turns" instead of "times", as demonstrated in the following example game. Note also that we are allowed to use the phrase "doing it" to mean "the same description as the previous one except for the part about turns or times", like so: "Waiting Room" The Antechamber is a room. The tattered copy of Women's Wear Daily is in the Antechamber. Instead of taking the Daily, say "It is stamped NOT TO BE TAKEN AWAY." Instead of examining the Daily for the first time, say "The best article seems to be about how your star sign affects your best swimsuit colour. Really: that's the best article." Instead of doing it for the second time, say "You now know a generous amount about a typical week in the life of a weather forecaster." Instead of doing it for the third time, say "You would now know how to cook herb bread, except that you have already forgotten the names of both of the herbs." Instead of doing it more than three times, say "Nope, you've drained it of all conceivable sustenance, even the small ads about French farmhouses to let (sleeps 7) and breast reduction surgery (with alarming photographs in sallow light)." After waiting for four to six turns, say "This is getting mighty dull." After waiting for seven to eight turns, say "Really, exceptionally dull." After waiting for nine turns, end the story saying "You have died of boredom, something previously thought medically impossible". Note once again that numbers above twelve must not be written out, so "more than twelve times" would be acceptable, but we would write "more than 13 times". 7.18. Postscript on actions In this chapter, all actions have been carried out by the player, all have been drawn from the standard stock of built-in actions ("unlocking", "taking", "going" and so forth), and all of those built-in actions have been allowed to work in the standard way - we have seen how to prevent the taking of something, and how to give this unexpected consequences, but not how to make taking work in an entirely different way. All three of those restrictions will later be lifted in the chapter on "Advanced Actions", but otherwise we have covered the ground thoroughly, and it is time to move on to the techniques enabling us to do more than make tart replies to the player: it is time to change the world. 7.19. Review of Chapter 7: Basic Actions 1. The concept of actions. The player's commands to the game are translated by Inform into actions: taking the bar of chocolate, going west, looking, and so on. Many actions apply to objects within the game world. The first object named in an action is called the "noun"; the second, the "second noun". If the player types >UNLOCK THE CEDAR BOX WITH THE TINY KEY Inform understands this command as the action "unlocking... with...", where the "noun" is the cedar box and the "second noun" is the tiny key. (The chapter on Understanding will explore how Inform interprets commands as actions.) A few actions apply to pieces of text instead of objects. For instance: >ASK LINDSAY ABOUT THE PIE Here Inform understands Lindsay as the "noun", but there is no "second noun". Instead, the "topic understood" is set to the text "the pie". The player could have typed absolutely anything here (ASK LINDSAY ABOUT DUTCH CLOG-DANCING, say), and we are reading the raw words he typed: we will only try to understand them later. Finally, actions can apply to values. The chapters on Advanced Actions and Understanding discuss how to create actions suitable to handle commands involving times, numbers, values, and so on, as in >WAIT UNTIL 10 PM >DIAL THE SAFE TO 1147 >SET THE PHASER TO STUN 2. Places to intervene. We may intervene in an action before it takes place, with a before or instead rule: Before taking the napkin, say... Instead of listening to Mozart: ... or we may wait until afterward and then add some additional response: After going to an unvisited room: ... After pushing the detonator button: ... In fact it is possible to meddle with the processing of an action at even more points, as we will see in the chapter on Advanced Actions. However, in practice the majority of simple changes to action behavior can be treated with one of these three types of rule. 3. Making an action happen. Sometimes we would like to make an action happen without the player having said so himself. In this case, we can write try opening the front door; silently try unlocking the safe; try silently unlocking the safe; These last two are equivalent. ("Silently" means that nothing will be printed unless the attempt at safecracking fails: it doesn't mean the player's character is being quiet in the fictional world.) 4. Built-in actions. All actions are listed in the Actions tab of the Index, and this is the easiest place to browse the selection built in. It is, of course, possible to define additional actions of our own, as we will see in the chapter on Advanced Actions. 5. Writing rules about actions. (a) Combinations of rules. Combined rules can apply to more than one different action: Instead of examining or looking under the sink: ... We may not (currently) combine objects in one rule, like this: Instead of examining the sink or the stove: ... We can however write rules that apply to anything matching some description. For instance, if we have a kind called "kitchen furnishing": Instead of examining a kitchen furnishing: say "It obviously has not been cleaned since Mrs. Closter gave up housekeeping for the family back in 1967." We may also write rules that apply to all actions on a single object, so: Instead of doing something to the Porsche: say "Your father is extremely protective of that machine. If it came to choosing between you or it, there's no real guarantee of the outcome." Finally, we can group together a whole range of actions under a single name: Jumping is loud behaviour. Shouting is loud behaviour. Eating the crisps is loud behaviour. and then write rules pertaining to that class of action: Instead of loud behaviour: say "Ssh! The baby is finally asleep!" (b) Circumstances. Rules about actions can also be constrained as to place, or spectators, or indeed any condition at all: Before touching something in the Antique Room: ... Instead of listening to something in the Loud Region: ... After doing something with the bomb in the presence of the guard dog: ... Instead of tasting something when the player is wearing the face mask: ... (c) Repetitions. We may also talk about the number of times an action has already occurred: Instead of listening to the radio more than once: ... Instead of tasting the squashed fruit for the second time: ... Instead of waiting for four turns: ... The last of these conditions requires that the turns be consecutive, while the first two do not. (d) Special conditions on Going. The "going" action is complex enough to have a number of extra conditions of its own, so we may talk about Instead of going to the House from the garden by the tricycle through the French doors with the wheelbarrow: ... where "to ..." indicates the room entered "from..." the room departed "by..." any vehicle transporting the player "through..." the door through which the player is passing "with..." any pushable item that the player is pushing along with him Chapter 8: Change 8.1. Change of values that vary So far, what we have done in response to the player's commands amounts to little more than a few ripostes. The simulated world does change during play, as the player moves from room to room or picks up things, but all of this is happening automatically, not at our direct instruction. How then can we make the world change? Recall that the world consists of rooms, in which are things, and that all of these have properties appropriate to their kinds. Some properties are either/or ("open" or "closed" but not both and not neither), while others have values (the "matching key" of a lockable door, for instance). Finally, we may also have created some free-standing values or "variables". We take the last example first, as it is the simplest. Suppose we have: "Winds of Change" The prevailing wind is a direction that varies. The prevailing wind is northwest. The Blasted Heath is a room. "Merely an arena for the play of witches and kings, my dear, where the [prevailing wind] wind blows." Instead of waiting when the prevailing wind is northwest: say "A fresh gust of wind bowls you over."; now the prevailing wind is east. The new phrase here is "now". This automatically checks that the new value is one which makes sense in the given context, so for instance it would not allow either of these: now the prevailing wind is 25; now the prevailing wind is the Heath; the former being a number, and the latter a room, so that neither is a direction. Similarly, "now" will not allow constant values to be changed. So Colour is a kind of value. The colours are blue, red and mauve. After pulling the psychedelic lever: now blue is mauve. ...will result in a problem message; it's like writing "now 1 is 2". The difference between "the prevailing wind" and "blue" is that the wind was declared to be a "direction that varies", whereas blue wasn't. (Beta release note) At present Inform allows:

change (a stored value) to (value)
or: change (object) to (property)
or: change (object) to (enumerated value)
This phrase changes the given stored value (a variable, table entry, property, or list entry) to the value supplied. Example: change the prevailing wind to south; This goes back to the very early days of Inform, before "now" was as flexible as it is today, and it is now deprecated. Future builds of Inform will withdraw it completely. "Now" can do anything "change" can do: now the prevailing wind is south; "change ... to ..." has a complicated definition (hence the three alternative forms) because it also allowed, for instance: change the location to visited; which didn't change the value of "location" at all, but instead gave that value the property of being "visited". This leads to awkward ambiguities, which are another reason for "change" being withdrawn. Again, "now" does this better: now the location is visited;
8.2. Changing the command prompt The command prompt is the text printed by Inform to ask the player for another command. Ordinarily this is simply a greater-than-sign, ">", so we tend not to notice it as text at all. Internally, though, it is a variable value called "command prompt", which means we can change it. For example, this will be a more conversational sort of prompt: When play begins: now the command prompt is "What now? ". Whereas this will be more up-to-the-minute and demanding: When play begins: now the command prompt is "[time of day] >". ("Time of day" is another variable value, which is fairly self-explanatory, but will be covered in detail later on.) The prompt can be changed at any point, so can be used to indicate the current situation, or even as a sly way to introduce a sort of conversation between computer and player. Example 113 (***): Don Pedro's Revenge Combat scenario in which the player's footing and position changes from move to move, and the command prompt also changes to reflect that. 8.3. Changing the status line The status line is the black bar along the top of a game being played, which ordinarily displays the current position, score and number of moves taken. Like the command prompt, it is not fixed but results from values which can be changed: the "left hand status line" and "right hand status line". The default values are "[the player's surroundings]" for the left hand status line and "[score]/[turn count]" for the right hand status line. Score and turn count are numbers which vary in play (more about scoring later); "[the player's surroundings]" is a text substitution really intended for just this purpose:

say "[the/-- player's surroundings]"
This text substitution produces a succinct description of where the player is, be this in darkness, in a lighted room or inside an opaque container such as a large packing case. Example: now the left hand status line is "You: [the player's surroundings]";
These make useful elements to juggle in redesigning the status line, as in the following example: When play begins: now the left hand status line is "[the player's surroundings] / [turn count] / [score]"; now the right hand status line is "Time: [time of day]". The text in the right hand status line should be kept no more than 14 letters long, including any spaces. The left hand status line has more leeway, but should still be kept brief. (See Awarding points for scoring.) Example 114 (*): Politics as Usual Have the status line indicate the current region of the map. Example 115 (***): Centered Replacing the two-part status line with one that centers only the room name at the top of the screen. 8.4. Change of either/or properties When we have an either/or property, we can set it like so: Instead of waiting when the oaken door is closed: say "There is a slow, creaky click! sort of noise as the door swings open, apparently all by itself."; now the oaken door is open. If it is open already, nothing changes: in any case nothing is said to the player unless we give explicit instructions to that effect, as we've done here. Inform protects its model world from accidental damage in several ways, one of which is to ensure that things are not given properties which they are not allowed to have. So this, for instance, will not be accepted: now the oaken door is unvisited More subtle problems arise if it is not possible to tell, when the game is being constructed, what the object in question will be: for instance, if we try to change a randomly chosen object to be "unvisited". Inform therefore makes additional checks during play, printing up a suitable message only if the rules are violated. The net effect is that it is impossible for the oaken door ever to have the "unvisited" property. Example 116 (*): Vitrine An electrochromic window that becomes transparent or opaque depending on whether it is currently turned on. 8.5. Change of properties with values Changing properties with values is very similar: now the printed name of the Closet is "Suddenly Spooky Closet" Inform checks three different things to ensure that this change is safe to perform. Firstly, the value must be the right kind for the property in question, so this for instance would be rejected: now the printed name of the Closet is 7 Secondly, the object in question has to be allowed to have the given property. This, for instance, would be disallowed: now the initial appearance of the Closet is "Dusty" (since "initial appearance" is a property which only things can have, not rooms). Finally, the object has to actually have the property, not just have the right to have that property. Thus: now the printed name of the Closet is "Suddenly Spooky Closet" ...is only permitted if the Closet is designed with a "printed name". In fact this is certain to be true: all rooms and things automatically have a printed name, which is the short boldface description in the case of rooms, and the usual text briefly describing something in the case of things. "Now" is a simple way to change many things in Inform, but it's cumbersome to change the map of the model world using "now", because the map is such a complicated arrangement. (It's not a property: it's a sort of mesh of relations.) So a special phrase exists to change map connections:

change (direction) exit of (room) to (room)
This phrase alters the map so that the given map connection is made. Note that connections can be made to rooms, but not doors: the positions of doors are fixed. Example: change the east exit of the Closet to the Tsar's Imperial Dining Salon Since "nothing" is not a room, this doesn't allow us to change the exit to nothing, so there is a separate definition of: change the west exit of the Closet to nothing

change (direction) exit of (room) to nothing/nowhere
This phrase alters the map so that the given map connection is unmade. Example: change the west exit of the Closet to nowhere
Altering the map itself is not a very subtle way to adjust when and where the player can move - writing suitable rules is usually a cleaner solution - so this phrase is best avoided unless really needed. Example 117 (*): Thirst A waterskin that is depleted as the player drinks from it. Example 118 (*): Thirst 2 A campfire added to the camp site, which can be lit using tinder. 8.6. Whose property? This seems a useful point to clarify something already seen. We normally call a property with a value something like: the printed name of the West Ballroom We are sometimes allowed to omit the "of the ..." part, and simply call it "the printed name", for the sake of brevity. For instance, the following room description: The West Ballroom is a room. "A handsome sweep of chequered floor beckons the eye into the [printed name]." will result in "West Ballroom" being substituted for "[printed name]". Since the text belongs to the West Ballroom, that is assumed to be the owner of any properties named in its description. Similarly: Instead of examining something, say "Hmm, let me see: [printed name]..." Here the owner of the "printed name" is assumed to be the noun referred to in the action - in other words, the "something" alluded to in the rule. 8.7. Moving things We have now seen how to change the properties of rooms and things, and also any freestanding values which may have a bearing on the model world. We are not allowed to change the kind of anything during play. Our remaining freedom is to move things around. It would make no sense to move rooms around, because rooms are the fixed reference points in our geography, but anything else is mobile. This even includes things which are supposedly "fixed in place", for unlike the player, we have god-like powers. (There are minor restrictions: backdrops are trickier to move, since they are present in several rooms at once - see the next section. And doors, at the junction between two rooms, cannot be moved.) Here is how to move something:

move (object) to (object)
This phrase moves the first-named object to the second. Example: move the genie's lamp to Aladdin's Cave; The first object named has to be a thing; the destination must be a room, as here, a container, a supporter, or a person. When something is moved, all its parts and contents (and all their contents, and so on) move with it. If the thing being moved is a person, then the destination is required to be a room or an enterable container. (In particular, a person cannot be carried by another person.) Two options can be used if the object being moved is the player. move the player to Aladdin's Cave, without printing a room description omits the description which would otherwise be produced. A compromise is to use: move the player to Aladdin's Cave, without printing an abbreviated room description which gives a full description if the player has never been here before, but only a brief one if it is a familiar scene. These options have no effect for any other objects being moved.
If the destination is a person, like so: move the genie's turban to Aladdin; then it will be carried rather than worn. We could arrange for it to be worn instead by writing now the genie's turban is worn by Aladdin; "Now..." is a much more flexible phrase than "move": more on this shortly. Example 119 (**): Meteoric I and II A meteor in the night sky which is visible from many rooms, so needs to be a backdrop, but which does not appear until 11:31 PM. 8.8. Moving backdrops A backdrop can be in several rooms at once. When created, its position can be given as any specific collection of rooms, or as a region, or even as "everywhere". For instance: The Upper Cave is above the Rock Pool. The Ledge is east of the Pool. The stream is a backdrop. It is in the Upper Cave and the Ledge. Moving backdrops is not like moving other things, because there's no single destination. There are several possibilities: (a) A backdrop can be moved to a region. If we define: Lower Level is a region. The Rock Pool and the Ledge are in the Lower Level. then we can write either of move the stream to the Lower Level; now the stream is in the Lower Level; and either way, the stream is now found in the Rock Pool and the Ledge but nowhere else. (b) A backdrop can be moved to a category of rooms:

move (object) backdrop to all (description of objects)
This phrase moves the backdrop so that it is now present in every room matching the given description. Example: If we define A room can be wet or dry. A room is usually dry. The Rock Pool is wet. then we can write move the stream backdrop to all wet rooms; This phrasing, "move the ... backdrop to all ..." is deliberately meant to look unlike the simpler "move ... to ...", to emphasise that this kind of movement is possible only for backdrops.
What then happens is that the stream is present in whichever rooms are currently wet. But the stream's position is ordinarily checked only after movements, for efficiency's sake. So if the player is in a room which suddenly changes from being dry to being wet, the stream will not magically appear (though it will be there if the player goes out and comes in again). If this is not good enough, the phrase "update backdrop positions" can be used to ensure the accuracy of all backdrop locations after a dramatic change:

update backdrop positions
This phrase runs through all backdrops in the model world and makes sure they are correctly in, or not in, the current location, so that everything appears right from the player's point of view. Example: The Upper Cave is above the Rock Pool. The Ledge is east of the Pool. The stream is a backdrop. When play begins: move the stream backdrop to all wet rooms. A lever is in the Cave. The lever is fixed in place. Instead of pulling the lever when the Cave is dry: now the Cave is wet; now the lever is in the Rock Pool; now the lever is portable; update backdrop positions; say "The old rusty lever pulls away, and the thin cave wall goes with it, so that a stream bursts into the cave, falling to the pool below."
(c) A backdrop can be removed from play, just as anything else can be: see the later section in this chapter. Example 120 (***): Orange Cones Creating a traffic backdrop that appears in all road rooms except the one in which the player has laid down orange cones. 8.9. Moving the player The player is a thing, too, and can also be moved, which has the effect of instantaneous transportation, without the need for a suitable map connection to the new location. For instance, these are equivalent: move the player to the Bodleian Library; now the player is in the Bodleian Library; This will ordinarily result in a room description of the Bodleian Library being printed up, but that might not always be desirable. For instance: Instead of waiting in the Schola Maleficorum: say "A bored demon catches your eye (they really do have very inquisitive fingers) and throws you back out into the Antechamber."; move the player to the Antechamber, without printing a room description. Thus tacking on the option "without printing a room description", remembering to add the comma, omits the description which would otherwise be produced. A compromise is to use the option "printing an abbreviated room description": this gives a full description if the player has never been here before, but only a brief one if it is a familiar scene. The player's point of view can also be moved by shifting to another character. Suppose the story features two people, Alice and Bob, and the player at the keyboard is giving commands to Alice, and seeing everything from her point of view. The phrase: now the player is Bob switches the perspective so that now Bob is the one controlled by the human player, and it's Bob's point of view which counts. The human being at the keyboard may feel a sense of having jumped abruptly from place to place, but in fact neither Alice nor Bob has moved. A change of player can sometimes cause confusing things to happen, if it takes place as part of a successful action. Suppose there's an action called "possessing", which enables the player to possess somebody else's body; and suppose the player types POSSESS ADELE. The action succeeds, so that the player moves into the mind of Adele. But that means that at the end of the action, the player is no longer the actor - that is, no longer the person who began the action; and consequently, Inform won't use the report rulebook to say what has just happened. It's a strange business, moving into another body. (Beta release note) In previous builds, changes of the player's perspective were also done using the following:

change the/-- player to (object)
This phrase switches the perspective so that the given person is now the point of view from whom the story is told. This is equivalent to: now the player is (object)
This wording is being removed as redundant, in common with most other uses of "change". Example 121 (***): Terror of the Sierra Madre Multiple player characters who take turns controlling the action. 8.10. Removing things from play Some things will occasionally be in a limbo state called being "off-stage": like actors or props not needed in Act II, but perhaps to be brought back on-stage later, they wait on the sidelines. Anything created with no apparent location will start the game off-stage, as in the case of the lamp here: Aladdin's Cave is a room. The genie's lamp is a container. (Such things are easy to see in the World index because they are listed after all of the rooms and their contents, not belonging inside any room.) To move something back on-stage, we simply "move" it back onto the stage set, so to speak: back to a room, or into, onto, or made part of something else which is currently on-stage. To remove something, we use the phrase:

remove (object) from play
Removes the given object from play, so that it is not present in any room. We are not permitted to remove rooms, or doors, or the player, from play; but we are permitted to remove backdrops, making them disappear from all rooms in which they are present. Example: remove the gold coin from play;
We can test whether something is on-stage or off-stage with: if the gold coin is on-stage, ... if the gold coin is off-stage, ... or could, for instance, write say "Ah, so many absent friends. Who now remembers [list of off-stage people]?" We can even write now the gold coin is off-stage which is equivalent the "remove the gold coin from play", and similarly for on-stage. (If we say "now the gold coin is on-stage" and it already was, nothing happens; if it wasn't, it is moved to the current location.) "On-stage" and "off-stage" are adjectives, like "visible" or "touchable", and they apply only to things. Rooms, directions and regions are the stage itself: so it makes no sense to ask the question of whether they are "on-" or "off-". Doors are always on-stage; backdrops are on-stage unless they have been explicitly removed using the "remove... from play" phrase. Example 122 (*): Beverage Service A potion that the player can drink. Example 123 (*): Spring Cleaning A character who sulks over objects that the player has broken (and which are now off-stage). Example 124 (**): Extra Supplies A supply of red pens from which the player can take another pen only if he doesn't already have one somewhere in the game world. 8.11. Now... "Now" has already appeared several times in this chapter, being used like a Swiss army knife to change values of all kinds: now the score is 100; In fact, "now" is by far the most flexible phrase known to Inform.

now (a condition)
This phrase makes the condition become true. Examples: now the score is 100; now the player is Kevin; now the front door is open; now Mr Darcy is wearing the top hat; now all the doors are open; now all of the things in the sack are in the box; Inform issues a problem message if the condition asks to do the impossible ("now 3 is an even number") or is vague ("now the duck is not in the Lily Pond") or not in the present tense ("now the front door had been open").
We've now seen all three things which can be done with a condition S which describes the world: S. - The relation holds at the start of play. if S, ...; - Does the relation hold right now? now S; - Make the relation hold from now on. For instance, The apple is in the basket. if the apple is in the basket, ...; now the apple is in the basket; Example 125 (*): Bee Chambers A maze with directions between rooms randomized at the start of play. Example 126 (**): Hatless It's tempting to use "now..." to distribute items randomly at the start of play, but we need to be a little cautious about how we do that. Example 127 (***): Technological Terror A ray gun which destroys objects, leaving their component parts behind. 8.12. Increasing and decreasing Once we begin to deal with named values (or table entries, list entries or other ways to describe places where values are kept), we find that we often want to change them. We could if we wanted always use "now" for this, but it can be a little clumsily worded if we want to increase or decrease something: now the score is the score plus six; Because of that, we have some convenient abbreviations which have the advantage that the value being changed only has to be named once:

increase (a stored value) by (value)
This phrases increases the variable, table entry, list entry, or property by the given amount, which must be of a compatible kind. Example: increase the score by 8; increase the time of day by 5 minutes;

decrease (a stored value) by (value)
This phrases decreases the variable, table entry, list entry, or property by the given amount, which must be of a compatible kind. Example: decrease the score by 6; decrease the carrying capacity of the player by 10;
An even greater abbreviation can be made when we are changing a number by 1 either way:

increment (a stored value)
This phrases increases the variable, table entry, list entry, or property by 1. Example: increment the score;

decrement (a stored value)
This phrases decreases the variable, table entry, list entry, or property by 1. Example: decrement the score;
"Increment" and "decrement" are traditional computing terms, though they have been used in engineering for at least a century and in finance for longer still. 8.13. Checking on whereabouts We have seen that while rooms are fixed, their contents move around, so we will need ways to examine the current whereabouts of things. The following examples show the kind of conditions allowed: if the genie's lamp is in Aladdin's Cave ... if Aladdin is not in Aladdin's Cave ... if Aladdin's Cave contains the genie's lamp ... if the genie's lamp is carried by Aladdin ... if Aladdin is carrying the genie's lamp ... if Aladdin does not have the genie's lamp ... if the table supports the genie's lamp ... if the table is supporting the genie's lamp ... if the genie's lamp is supported by the table ... if the genie's lamp is on the table ... if the genie's lamp is on top of the table ... if the genie's lamp is in the cupboard ... if the genie's lamp is contained in the cupboard ... if the genie's lamp is inside the cupboard ... if the genie's lamp is within the cupboard ... if the wick is part of the genie's lamp ... As the previous section mentioned, these are exactly like the assertions which we use to set up the world, except that we make them questions by placing "if" in front. But we shall later see that we can also use three other tenses, not to mention plural forms, so that new verbal forms like "had not been inside" and "were not supported by" are legal here (which they would not be in assertions). What we are not allowed is to contract these verbs with apostrophes: "isn't", "hasn't" and "hadn't" are forbidden. Overwhelmingly the condition we check most is whether the player is carrying something. The following are therefore equivalent: if the genie's lamp is carried by the player ... if the genie's lamp is carried ... And similarly for "not carried", "worn" and "not worn". To be precise, if a form of to be carried or to be worn is not followed by any other description, then "the player" is assumed to be doing the carrying or wearing. 8.14. More flexible descriptions of whereabouts The examples just given were all basically of the form "X relation Y" where X and Y were specific names of things. For example, if the genie's lamp is carried by Cinderella ... if the genie's lamp is inside the cupboard ... Just as actions could be described with patterns to be matched ("taking an open container", say), so can the positions of things. Giving subtler descriptions of our X and Y sometimes broadens the possibilities, sometimes narrows them: if the genie's lamp is carried by a woman ... if the genie's lamp is inside the closed cupboard ... In the first case, Y is allowed to be one of a whole range of things - any of the women existing in the world. This makes for a broader condition. In the second case, Y has not only to be the cupboard, but at a time when it is closed: which makes for a narrower condition. We can, of course, also vary X: if an animal is inside the cupboard ... if a container is carried ... And we can even vary both X and Y at once: if a woman is holding an animal ... a condition which will be true if, anywhere in the game's world, any woman is holding any animal. 8.15. Calling names Conditions like "if somebody is in an adjacent room" allow complicated tests to be performed with a minimum of fuss, but it's rare that we want to know only whether they are true: more likely we also want to know which person, and which room. For this purpose, we are allowed to supply a name for any such vaguely-described object which comes up, and then to use that name thereafter. if somebody is in an adjacent room (called the Hiding Place), say "You hear distant breathing from [the Hiding Place]." We can even name more than one of the things discovered: Instead of waiting when a woman (called the kidnapper) is holding an animal (called the pet), say "How can you think of rest when, somewhere out there, [pet] has been cruelly kidnapped by [the kidnapper]?" Note the brackets, which are essential. The result of typing "wait" is then How can you think of rest when, somewhere out there, a lapdog has been cruelly kidnapped by Baroness Orczy? Of course, that might be just one of many animals held by women in the game. We shall later see ways to go through all of the possibilities found, performing some action with each in turn. A calling, if we can use that word, should be made immediately after the noun it refers to, and not left to hang back after any relative clauses. For instance, if something (called the penitential object) held by the player is hot is allowed, but not if something held by the player (called the penitential object) is hot because there is too much potential ambiguity - are we trying to call the player something? (See Repeat running through for systematically working on everything matching a description.) Example 128 (*): Higher Calling All doors in the game automatically attempt to open if the player approaches them when they are closed. 8.16. Counting the number of things It is very often useful to know how many things are in a given situation, and for this purpose we have the "number of ..." construction. For instance: the number of edible things carried the number of things on the table the number of people in the Dining Room Whereas "a woman is holding an animal" makes the same test as "an animal is held by a woman", getting the same result, counting is not so even-handed: the number of women holding animals the number of animals held by women are different questions and, unless the ration is strictly one lapdog per baroness, will have different answers. If Cruella de Vil has 101 dalmatians, they may be very different indeed. It can also be helpful to count things with no particular location, like so: the number of rooms the number of closed doors For instance: When play begins, change the right hand status line to "Explored: [number of visited rooms]/[number of rooms]". Provided that the possible range is finite, we can also use "number of" to count values which match a description. For instance: the number of non-recurring scenes or if we were to define Colour is a kind of value. The colours are red, orange, yellow, green, blue, indigo and violet. then "the number of colours" would evaluate to 7. As with other ways of talking about whole ranges of values, this only works if the range is manageable. "The number of numbers" cannot sensibly be worked out: there are infinitely many, for all practical purposes, and similarly for "the number of texts". 8.17. Looking at containment by hand The descriptions outlined in the last few sections are intended to deal with almost all of the routine questions we might have about what currently resides where. It should be a last resort to use the following more primitive way to inspect the world.

holder of (object) ... object
This phrase produces the container, supporter, carrier, wearer or room in which the object resides.
It's sometimes useful to go the other way. When something has possessions, we can find them out one at a time by running through a list.

first thing held by (object) ... object
This phrase produces the first of the list of things held by the object. Example: first thing held by Baroness Orczy

next thing held after (object) ... object
This phrase produces the next item of the list of things held by something. Example: suppose Baroness Orczy is carrying a lapdog and a string of pearls. next thing held after the lapdog is then the string of pearls.
8.18. Randomness Sometimes we want to introduce random behaviour into play. We usually do this by generating random values, and then acting differently depending on what they are. The following: a random number from 2 to 5 produces, as it suggests, a random number drawn from the choices 2, 3, 4 or 5, each of which is equally likely to come up. In fact, this isn't limited to numbers:

a random (name of kind) between (arithmetic value) and (arithmetic value) ... value
or: a random (name of kind) from (arithmetic value) to (arithmetic value) ... value
or: a random (name of kind) between (enumerated value) and (enumerated value) ... value
or: a random (name of kind) from (enumerated value) to (enumerated value) ... value
This phrase produces a uniformly random value in the range given. Examples: a random number from 10 to 99 a random time from 2:31 PM to 2:57 PM If we make a new kind of value: A cloud pattern is a kind of value. The cloud patterns are cumulus, altocumulus, cumulonimbus, stratus, cirrus, nimbus, nimbostratus. then we can also take random values from it: a random cloud pattern between stratus and nimbus which has three possible outcomes, all equally likely.
We can also use random conditions:

if a random chance of (number) in (number) succeeds:
This condition is true X/Yths of the time, where X and Y are the numbers. Example: if a random chance of 2 in 3 succeeds, ... Here is a rule which applies only 15% of the time: Instead of waiting when a random chance of 15 in 100 succeeds: ...
Testing IF which makes random choices can be rather frustrating, because a problem showing up on one attempt may not show up on another. We can get around this by making use of the fact that computers do not actually generate true randomness, but instead make a sequence of apparently random numbers by applying a complicated formula to each one in order to make the next. The starting point is a number called the "seed", because the next choice grows out of it.

seed the random-number generator with (number)
This phrase changes the seed number as specified. Any random numbers generated after that depend only on the seed. Example: the following sentence will "fix" the process of generating these random numbers so that they are not random at all - the same sequence of random numbers will be produced on each run. When play begins, seed the random-number generator with 1234. The seed value "1234" can be anything positive; a different sequence of random numbers will be produced for each different seed value. A seed value of 0 restores the RNG to properly random behaviour again.
Alternatively, it's possible the "fix" the RNG by clicking the "Make random outcomes predictable when testing" option on the Settings panel. This makes the behaviour predictable whenever the game is played within Inform, but (unlike the rule above) has no effect on the story file once released. Example 129 (*): Do Pass Go A pair of dice which can be rolled, and are described with their current total when not carried, and have individual scores when examined. Example 130 (*): Lanista 1 Very simple randomized combat in which characters hit one another for a randomized amount of damage. Example 131 (*): Weathering The automatic weather station atop Mt. Pisgah shows randomly fluctuating temperature, pressure and cloud cover. Example 132 (***): Uptown Girls A stream of random pedestrians who go by the player. 8.19. Random choices of things Writing "a random number" is not allowed, because the possible range is too large, but that was the only reason why not.

a/-- random (description of values) ... value
This phrase makes a uniformly random choice from values satisfying the description given. Example: a random visited room a random scene A problem message is issued if the range is too large (for instance, "a random text"). Unexpected results may follow if no value fits the description, unless we are describing objects, in which case the result is the special value "nothing".
For instance: say "You can see [number of adjacent rooms] way[s] from here; how about [random adjacent room]?" But it's important to worry about the possibility that nothing qualifies - here, that no adjacent rooms exist. The above would then say: You can see 0 ways from here; how about nothing? Example 133 (*): Candy One of several identical candies chosen at the start of play to be poisonous. Example 134 (*): Zork II A "Carousel Room", as in Zork II, where moving in any direction from the room leads (at random) to one of the eight rooms nearby. 8.20. Review of Chapter 8: Change 1. Things that vary. A "variable" is a named value which changes as time goes by. In this chapter, we saw only one of the two sorts of variable: a value which exists throughout the whole game. For instance: The prevailing wind is a direction that varies. The current horse is an animal that varies. The last remark is some text that varies. The previous item is a thing that varies. (In the chapter on Phrases we shall later see that is also possible to have named values that exist only temporarily, using the "let..." phrase.) A variable always has a kind - sometimes a kind of object, like "a direction" or "an animal" or "a thing", and sometimes a kind of value, like "some text" or "a number". 2. Now. We may change values using "now": now the prevailing wind is east; now the current horse is Comet; Several pre-defined variables can be altered this way to affect the way the game appears or plays: now the command prompt is "And then? "; now the left hand status line is "[time of day]"; now the right hand status line is "[score] / [turn count]"; But "now" is far more powerful: now the oaken door is closed; now the printed name of the Closet is "Scary Closet"; now the brightness of the lamp is flickering; now the player is in the South Corridor; now the player wears the hat; now the oaken door is closed; It is also able to give instructions for multiple items, using descriptions: now all the doors are open; now everything in the sack is in the box; now every woman loved by Brisco is angry; 3. Player. The "player" is a person that varies. Most source texts never say anything about who the player is, and then Inform creates a "yourself" person to be the player: someone of kind "person", not "man" or "woman", so that no gender is established, and who will be nondescript in appearance. We could instead specify any of the people in the source text to be the player: Lord Bowler is a man in the Pavilion. The player is Lord Bowler. We can even switch to the point of view of a new protagonist during play: now the player is Lady Deep-Gulley; The player's commands will then control this new character, wherever he or she may be. (Lord Bowler, no longer responding to commands, will remain where he was at the time of the switch unless we explicitly move him off-stage.) 4. Moving things around the map. We may move things (and the player) around the world with such phrases as move the hat to the wardrobe; move the player to the San Francisco; move the player to the Moon, printing an abbreviated room description; move the player to the North Hall, without printing a room description; remove the penny black from play; We may also check whether something is outside the scope of the game with if the gold coin is off-stage, ... if the gold coin is on-stage, ... A thing will be on-stage if its location is a room (that is, if Inform can find a room that directly or indirectly contains the item). Otherwise, it will be off-stage. 5. Checking locations. By default, things in Inform games relate to one another physically by to contain - containment relation to support - support relation to carry - carrying relation to wear - wearing relation to be part of - (reversed) incorporation relation to incorporate - incorporation relation to be adjacent to - adjacency relation to have - to either carry or wear, which we call the possession relation to enclose - an indirect containment/support/incorporation relation to hold - a direct containment/support/incorporation relation (We have met these before in the chapter on Things, and will review them further in the Relations chapter.) We may check on the state of any of these relations like so: if the bottle contains whiskey, ... if the bar supports a ten-dollar gold piece, ... if the player carries a six-shooter, ... if Daisy is wearing a corset, ... if the Gilded Rod is part of the Time Orb, ... if the location is adjacent to the Train Yard, ... if a bounty-hunter has a warrant, ... if the Saloon encloses a gun-slinger, ... if Daisy is holding the infant Emperor of China, ... The "holding relation" includes containment, support, incorporation, wearing, and carrying, all in a single idea; so it is sometimes convenient to be able to talk generically about the holder of something. In the preceding examples, for instance: the holder of the emperor = Daisy the holder of the Gilded Rod = the Time Orb 6. Callings. Since the descriptions used in these conditions can be open-ended, it is sometimes useful to keep track of what specific things were found, using the "(called...)" construction. Here we check for the existence of a certain kind of bounty-hunter, and remember his name if he exists: if a bounty-hunter (called the current bounty-hunter) has a warrant, say "[The current bounty-hunter] watches you suspiciously." We can do the same thing in defining rules: Instead of attacking a dangerous man (called the victim) when the player is unarmed: say "You rush at [the victim], who knocks you down with a well-aimed swing." When we use "(called ...)", we create a new value or thing that varies - this is an example of a value which lasts only for temporary usage, but it can be used in the rest of the rule currently being defined. Chapter 9: Time 9.1. When play begins With the material from previous chapters, we are now able to set up a simulated world, to respond to the player's actions within it, and to make it change in perhaps unexpected ways. The resulting experience can be as lively as we want to make it, but so far we have no very good ways to give it any structure: a beginning and an end, for instance, or a sense of plot. This next chapter is all about the passage of time, and it begins at the beginning. We have already seen an example of how to write a rule which applies just once, at the start of the game: When play begins: say "Welcome to Old Marston Grange, a country house cut off by fog." The "when play begins" rules are checked only at the start of a game, not when a saved session is restored from disc. What happens is that these rules are followed, then the game's banner is printed, then the initial room description is printed up, and then the player is asked for a first command. Example 135 (*): Clueless A murderer for the mystery is selected randomly at the beginning of the game. 9.2. Awarding points Traditionally-written games award points throughout play, as an indication of progress. If we want to be traditional, we can award points as follows: increase the score by 5; substituting whatever number we feel is appropriate. We should be careful not to give out the same points over and over, that is, not to reward the same basic achievement many times over if the player simply repeats the same action. This, for instance, is open to abuse: After taking the trophy: increase the score by 5; say "Well done!" The player may simply take the trophy, drop it again, take it again, ... and win five points every time around. We can prevent this by phrasing the rule more carefully: After taking the trophy when the trophy is not handled: increase the score by 5; say "Well done!" Rather than being an open-ended scoring system, IF normally has a maximum possible score, which can be specified with a sentence like so: The maximum score is 10. The score and maximum score are just numbers that vary, so we can freely change them: After eating the poisoned mushroom: now the score is -100. Recall that if the source declares: Use no scoring. then the SCORE, NOTIFY ON and NOTIFY OFF commands do not work; the final score is not shown at the end of a game; and the status line above the player's text area shows only the turn count, not (as is more usual) both the score and the turn count. Changing the "score" has no visible effect, though it is not actually illegal. (Beta release note) In previous builds, Inform had a special phrase for adding to the score:

award (number) point/points
This phrase adds the given value to the score. It is now deprecated, and only ever acted as a shorthand for: increase the score by (number) Giving this a special phrase wording tended to suggest to newcomers that there was something special about the score - when, in fact, it was only ever a number that varies, called "score".
Example 136 (**): Mutt's Adventure Awarding points for visiting a room for the first time. Example 137 (***): No Place Like Home Recording a whole table of scores for specific treasures. 9.3. Introducing tables: rankings Another tradition of interactive fiction is that the player has a current 'rank' according to how far his or her score has got. We can (but need not) choose to provide such rankings, and should do so by specifying a table like this: Table 1 - Rankings Score Rank 0 "Beginner" 25 "Amateur Adventurer" 50 "Novice Adventurer" 100 "Junior Adventurer" 200 "Adventurer" 300 "Master" 330 "Wizard" 350 "Master Adventurer" Typographically, tables in Inform look as much as possible like those found in non-fiction books: they can have many columns, so this is only a simple example (drawn from the actual rankings used by Infocom's Zork I, 1979). Each line in the source represents one row in the table, and the entries on a line must be separated by at least one tab character. (An entry might of course have several words with spaces in between, so a space is not enough to separate entries: this is the only context when Inform distinguishes between spaces and tabs.) The table must occupy a single whole paragraph, with no skipped lines or missing entries. We are free to use extra tabs to indent it if we like. Ordinarily we must explicitly ask to use the information presented in a table, but the table of rankings is a special case: Inform uses it automatically, if it is provided at all. To be recognised it must have the name "Rankings" and must have two columns named and arranged as shown. The scores should be given in ascending order. Customarily, the score in the final row should be the maximum possible achieved in the game - so that only a player with maximum possible score can be awarded the final ranking - and the value of "maximum score" is automatically set to this bottom-row value if it has not been explicitly set anywhere else in the source text. 9.4. When play ends Short of something like a power cut, the game can only end when one of the two participants chooses to end it: either the player, by deciding that enough is enough, or us. In story-telling, there are many kinds of ending: happy, sad, decisive, bittersweet, surprise. Inform doesn't try to interfere in that kind of artistic choice, but it does need to know one thing about the ending: is it final, or not? Many authors like to make additional menu items available if the player has completed the story right through, but not if she has reached an early or wrong ending. (See the activity "amusing a victorious player", for example.)

end the story
This phrase ends the story at the next opportunity (typically as soon as the current rule ends), with the closing message "The End." The end is not considered final.

end the story finally
This phrase ends the story at the next opportunity (typically as soon as the current rule ends), with the closing message "The End." The end is considered final, and any hidden menu options will be revealed.

end the story saying (text)
This phrase ends the story at the next opportunity (typically as soon as the current rule ends), with the closing message given in the text. The end is not considered final. Example: end the story saying "You have been stymied"

end the story finally saying (text)
This phrase ends the story at the next opportunity (typically as soon as the current rule ends), with the closing message given in the text. The end is considered final, and any hidden menu options will be revealed. Example: end the story finally saying "You have defeated Sauron"
The closing message is traditionally set out in asterisks: *** The End *** This style is traditional in IF, and go back to 1980 if not earlier. We can test the current state like so:

if story has ended:
This condition is true if an end has been declared using one of the "end the story..." phrases.

if story has not ended:
This condition is true if no end has been declared using one of the "end the story..." phrases.

if story has ended finally:
This condition is true if an end has been declared using one of the "end the story finally..." phrases, so that an ending has been reached which the author feels is a completion of the player's experience.

if story has not ended finally:
This condition is true if an end has been declared using one of the "end the story..." phrases, but not "finally", so the author feels that the player can get further experience by playing again and trying different approaches.
The rulebook "when play ends" is the matching bookend to "when play begins". It is followed when the game decides to end (not when the player simply gives up and quits), and before any epitaph like *** You have been poisoned *** appears. For example: When play ends, say "Oh dear." Surprisingly, the end is not always the end:

resume the story
This phrase causes an ended story to resume exactly as if no "end the story..." phrase had been used. Example: When play ends: if the story has not ended finally: say "Oh dear. Still, here's another chance."; resume the story. The phrase is likely to be sensible only as part of a "when play ends" rule. Other traditional uses include giving the player three lives, as in an old-school arcade machine.
(Beta release note) In earlier builds of Inform, the wording of these phrases was different. There was only one possible way to end finally, which caused some authors trouble, but otherwise the functionality was about the same. The change was really made to recognise that modern IF is about story-telling, and shouldn't assume that everything is a matter of life and death. The following shows the old, now deprecated, wording, together with equivalents in the new wording:

end the game saying (text)
A phrase now deprecated and equivalent to: end the story saying ...;

end the game in death
A phrase now deprecated and equivalent to: end the story saying "You have died";

end the game in victory
A phrase now deprecated and equivalent to: end the story finally saying "You have won";

resume the game
A phrase now deprecated and equivalent to: resume the story;

if game ended in death:
A phrase now deprecated and equivalent to: if the story has ended and the story has not ended finally, ...

if game ended in victory:
A phrase now deprecated and equivalent to: if the story has ended finally, ...

if game is over:
A phrase now deprecated and equivalent to: if the story has ended, ...

if game is in progress:
A phrase now deprecated and equivalent to: if the story has not ended, ...
Example 138 (***): Big Sky Country Allowing the player to continue play after a fatal accident, but penalizing him by scattering his possessions around the game map. 9.5. Every turn The passage of time in interactive fiction is broken up into a succession of turns, in each of which the player types a request and is given a response. Usually each such request triggers one action, but sometimes a whole sequence are fired off, as when the player types "get all" in a cluttered room. As we've seen, the variable "turn count" holds the number of turns of play so far. By convention turn number 0 is the time when Inform prints up the banner and any initial text; it becomes turn number 1 when the player's first command is typed. One of the last things to happen in each turn is that Inform will apply any rules which have been set to occur "every turn", like so: Every turn, say "The summer breeze shakes the apple-blossom." This is equivalent to writing: An every turn rule: say "The summer breeze shakes the apple-blossom." Note that the text about blossom, which will quickly become tiresome, is said at the end of every turn, not at the beginning, and in particular not before the player's first opportunity to type a command. As usual when defining rules, we can add stipulations: any condition can be attached using "when". Every turn when in the Orchard, say "The summer breeze shakes the apple-blossom." Every turn when the player can see the rotting fish, say "Your nose twitches involuntarily." Example 139 (***): Witnessed 1 A kind of battery which can be put into different devices, and which will lose power after extended use. Example 140 (****): Text Foosball A game of foosball which relies heavily on every-turn rules. 9.6. The time of day Inform keeps track of the time of day automatically: play ordinarily begins at 9 AM and each turn takes one minute. In some works of interactive fiction, time of day is crucial: in others, it is irrelevant or even, by a sort of tacit convention, non-existent. So Inform does nothing to act upon the time, or to reveal it to the player, without instruction. Nevertheless it is there. A sentence like the following allows the initial time to be set up as something other than 9 AM: The time of day is 3:13 PM. Here, "3:13 PM" is a constant value of a kind not seen before: it's a kind of value called "time", and the value "time of day" is a time that varies. After one turn it will be 3:14 PM, then 3:15 PM and so on. Note that the sentence above is an assertion (a statement about the initial state of affairs), not an instruction which can be part of a rule. It would be equivalent to write: When play begins: now the time of day is 3:13 PM. We more often change "time of day" to take care of drastic events: At the time when the player loses consciousness: now the time of day is 10:12 AM; say "A mist comes over your vision, and when you come to, it is morning and you are in bed." Example 141 (**): IPA Shops which each have opening and closing hours, so that it is impossible to go in at the wrong times, and the player is kicked out if he overstays his welcome. 9.7. Telling the time Now that we have the time of day, we can of course use this value in room descriptions and the like: The Clock Chamber is a room. "The dark chamber behind the clock face, a mill-room of gears which grind down the seconds. Through the glass you can see the reversed hands reading [the time of day]." It seems odd, though, to read a precise numerical description of the time here: after all, it isn't a digital clock. A friendlier version would use:

say "[time in words]"
This text substitution produces the given time written out in English sentence form. For example: "Through the glass you can see the reversed hands reading [the time of day in words]." might produce Through the glass you can see the reversed hands reading twenty to nine.
To reiterate an example which came up earlier, we could even work the time of day into the command prompt, which would lend the proper sense of urgency to a game played out against the clock: When play begins: now the command prompt is "[time of day] >". Example 142 (*): Situation Room Printing the time of day in 24-hour time, as in military situations. 9.8. Approximate times, lengths of time Clocks and watches vary considerably in how much detail they show, and we tend not to report the time over-precisely: half-past ten is an elastic concept. The following room description for the Clock Chamber comes across much more naturally: The Clock Chamber is a room. "The dark chamber behind the clock face, a mill-room of gears which grind down the seconds. Through the glass you can see the reversed hands reading [the time of day to the nearest five minutes in words]." The phrase "... to the nearest ..." rounds off the given time, just as it sounds; as we'll see later, it can actually round off any arithmetic values, not just times. For instance, "9:58 PM to the nearest ten minutes" is 10:00 PM. In talking about lengths of time, rather than times of day, it's useful to have these:

(number) minutes ... time
This phrase converts numbers into lengths of time. Example: 15 minutes Because it's a phrase, not just a notation for writing constants down, the number doesn't have to be given literally: let X be 5; if the player is in the Slow Room, now X is 10; let deadline be the time of day plus X minutes; Note that lengths of time can't exceed 1440 hours.

(number) hours ... time
This phrase converts numbers into lengths of time. Example: 10 hours Note that lengths of time can't exceed 24 hours.
9.9. Comparing and shifting times Carrying out easy calculations with times is straightforward: The chronometer is in the Clock Chamber. "On one wall is a terribly self-important chronometer showing the time in major world cities. London: [time of day]. Paris: [one hour after the time of day]. Tokyo: [9 hours after the time of day]. Cupertino, California: [7 hours before the time of day]." Here we are using two phrases:

(time) before (time) ... time
This phrase produces a time earlier by the amount given, keeping within the 24 hour clock. Example: 7 hours before 5:30 AM produces 10:30 PM.

(time) after (time) ... time
This phrase produces a time later by the amount given, keeping within the 24 hour clock. Example: 9 hours after 11 AM produces 8 PM.
Similarly, we have conditions:

if (time) is before (time):
This condition is true if the first time occurs earlier in the day than the second. In recognition of the fact that very few stories begin before 4 AM, whereas many run on past midnight, the start of the day is taken to be 4 AM: thus 3:59 AM is after 11:10 PM, but 4:04 AM is before it.

if (time) is after (time):
This condition is true if the first time occurs later in the day than the second. In recognition of the fact that very few stories begin before 4 AM, whereas many run on past midnight, the start of the day is taken to be 4 AM: thus 3:59 AM is after 11:10 PM, but 4:04 AM is before it.
(Beta release note) Previous builds of Inform allowed the following abbreviated forms, but they're being withdrawn in the interests of clarity:

if it is before (time):
This condition is equivalent to: if the time of day is before (time) and is now deprecated: use the "time of day" wording instead.

if it is after (time):
This condition is equivalent to: if the time of day is after (time) and is now deprecated: use the "time of day" wording instead.
9.10. Calculating times We will occasionally need to perform more complex calculations with time, and in order to do that, we have a way to convert the time of day to numbers. Thus the phrase "the minutes part of ..." takes a time and produces a number from 0 to 59; similarly "the hours part of ..." extracts a number from 0 to 23, using the twenty-four hour clock. To go the other way, we can convert any number to a duration by writing "minutes" or "hours" after it. For instance:

minutes part of (time) ... number
This phrase converts a time to a number, then takes the result mod 60, which in effect produces the number of minutes after the hours are thrown away. Example: minutes part of 12:41 PM produces 41.

hours part of (time) ... number
This phrase converts a time to a number, then divides the result by 60, which in effect produces the number of hours after minutes are thrown away. Example: hours part of 8:21 AM produces 8.
For example: The clock error is a number that varies. To thump the mechanism: now the clock error is a random number from -10 to 10. The broken grandfather clock is in the Chamber. "An erratic grandfather clock seems to say it is [clock error minutes after the time of day]." When play begins, thump the mechanism. Instead of attacking the broken clock: thump the mechanism; say "You thump the clock, which now reads [clock error minutes after the time of day].". Note that "clock error" is a number, but "clock error minutes" is a time. 9.11. Future events We often want to arrange for something to happen at some point in the future. Here is yet another timepiece: An egg-timer is in the Chamber. "A plastic egg timer in the shape of a chicken can be pressed to set it going." Instead of pushing the egg-timer: say "It begins to mark time."; the egg-timer clucks in four turns from now. At the time when the egg-timer clucks: say "Cluck! Cluck! Cluck! says the egg-timer." The event here is called "the egg-timer clucks". It only happens if we instruct so, using one of the following phrases:

(rule) in (time) from now
This phrase causes the given rule to be run at a given time offset from the current time of day. Example: the egg-timer clucks in 18 minutes from now;

(rule) in (number) turn/turns from now
This phrase causes the given rule to be run at a given number of turns after the current one. Example: the egg-timer clucks in four turns from now;

(rule) at (time)
This phrase causes the given rule to be run at a given time of day. Example: the egg-timer clucks at 11:35 AM;
If we know in advance what time we want something to happen, we can more simply write: At 4 PM: say "The great bells of the clock tower chime four." (Note that in either case such rules begin with the word "at": they are the only rules allowed to begin with the word "at".) Example 143 (*): MRE Hunger that eventually kills the player, and foodstuffs that can delay the inevitable by different amounts of time. Example 144 (**): Totality To schedule an eclipse of the sun, which involves a number of related events. Example 145 (**): Empire A train which follows a schedule, stopping at a number of different locations. Example 146 (***): Hour of the Wren Allowing the player to make an appointment, which is then kept. 9.12. Actions as conditions There are two ways that descriptions of actions can be used as conditions. First, we can simply describe an action, and then the condition will be true if that is what the player is trying to do, and not otherwise: if taking a container, ... This is actually an abbreviation for the longer, some would say preferable form: if we are taking a container, ... Secondly, we can talk about the past as well as the present, which is very useful since interactive fiction often contains situations which are changed by earlier events. Instead of waiting when we have taken the lantern, say "No, your acquisitive nature is roused now, and simply waiting will no longer do." More on the past tense later follows in the next section: note that "we are taking" has become "we have taken". For the rule to apply, it is not enough that the action "taking the lantern" has been tried: it must have succeeded. Example 147 (*): Night Sky A room which changes its description depending on whether an object has been examined. Example 148 (***): Zero A box which called "horribly heavy box" after the player has tried to take it the first time. 9.13. The past and perfect tenses The remaining sections of this chapter go into more technical ways to think about the progress of the game through time, and can be skipped at a first reading. Conditions are clauses which require Inform to make a decision: is such-and-such true, or not true? We have already seen conditions attached to rules using "when": Instead of waiting when the Sorting Hat is in the Hall: ... and, as we shall later see, we will often want to write instructions like: if the Sorting Hat is in the Hall, say "Hermione blinks apprehensively." The condition is "the Sorting Hat is in the Hall", and during play this will sometimes be true and sometimes false. A condition in the form "X is Y" is of course written the present tense, and refers to the current state of affairs. Three other tenses are allowed. First, the present perfect: if X has been Y ... is true if it has ever been the case that "X is Y" at the start of any turn (or any action). So, for instance, if the gate has been open ... will be valid if and only if the gate has ever been made open by any action (even if it is closed now), or if it started out by being open when play began. Next is the past tense: if X was Y ... holds if and only if "X is Y" was true at the start of the most recent action. This is convenient when trying to describe what has changed in the course of the action, but sometimes also when making the action itself happen. For instance: if the lantern was switched on, now the lantern is switched off; if the lantern was switched off, now the lantern is switched on; Completing the set is the past perfect: if X had been Y ... which records whether "X has been Y" was true at the start of the most recent action. All these verbs can of course be negated (though "wasn't" and "hadn't" are disallowed as poor style: we use "was not" and "had not" instead). So for example, if the player had not been in the Ballroom ... is true if the player hadn't visited the Ballroom at the start of the most recent action. Something we must watch out for is that variables might not have the same values in the past that they have now. As a result, writing conditions such as "if the noun has been open" is a bad idea, because in the past "the noun" very likely referred to something different. It is really only safe to talk in the past tense about definite, fixed things: "if the Great Gates of Kiev have been open" would be fine. Example 149 (*): Tense Boxing An overview of all the variations of past and present tenses, and how they might be used. Example 150 (**): Elsie A door that closes automatically one turn after the player opens it. Example 151 (**): Bruneseau's Journey A candle which reacts to lighting and blowing actions differently depending on whether it has already been lit once. 9.14. How many times? There are two further ways to examine the historical record. Given any condition, we can say if (...condition...) for the second time ... if (...condition...) twice ... if (...condition...) 2 times... if (...condition...) two times... (all of which are synonymous: the words once, twice, thrice, one, two, three, four, five, six, seven, eight, nine, ten, first, second, third, fourth, fifth, sixth, seventh, eighth, ninth and tenth all mean what they obviously should). The result is true if the condition holds now and has held for only one previous spell in the past. A condition holding for, say, fifteen consecutive turns without a break counts as only one "time" - so what we mean by "twice" here is that it is true now, was previously false for a while, and was previously true for a while before that, but no more. In effect, then, if the player is in the Ballroom for the third time ... is true if this is the third visit to the Ballroom. We can also say if the player is in the Ballroom for more than the third time ... or similarly "less than", "at least", "at most". It would be more natural, though, to say if the player has been in the Ballroom three times ... The adjective "only" (or equivalently "exactly") can be added to obtain if the player has been in the Ballroom only three times ... To recap, this means there have been exactly three visits to the Ballroom in history, whereas if the player is in the Ballroom for the third time ... means there have been exactly three visits, the third of which is still going on - an important distinction. Example 152 (*): Infiltration A room whose description changes depending on the number of times the player has visited. 9.15. How many turns? So much for "times" - spells in which a condition is true. We can also test the length of time, in turns of play, that something has been true. Thus: if ... for three turns; means that the condition holds now, and held at the start of this turn, at the start of last turn, and at the start of the turn before that. In particular: if the floppy hat has been worn for three turns ... will be false if the hat is not currently worn (even if it has been often in the past) and, on the other hand, will be true if the hat has been worn for twenty turns. Here again we can be more specific. These are synonymous: if the floppy hat is worn for the third turn ... if the floppy hat has been worn for only 3 turns ... if the floppy hat has been worn for exactly three turns ... all requiring that the hat wasn't worn four turns ago. As before, "more than", "less than", "at least" and "at most" so forth can also be used - say, "for at least 21 turns". A warning: we must be careful when writing something like if the noun has been open ... since this tests whether it has ever been true that the noun of the then action was open: not whether the current noun-object has ever been open. Lastly, note that the beginning of play - when (usually) initial text and a banner is printed, followed by a room description - counts towards these counts. In effect, this is a turn: one in which the player compulsorily performs the looking action, rather than being asked for a command. (By convention it is numbered as turn number 0, and doesn't contribute towards the turn count.) Example 153 (*): Annoyotron Jr A child who after a certain period in the car starts asking annoying questions. 9.16. Review of Chapter 9: Time 1. Beginning and ending the game. Every rule has a circumstance attached for when it should take place. Some happen when certain actions are being tried, like taking something. Others happen at special times. The simplest of these are the rules which happen "when play begins", or "when play ends": When play begins: say "Welcome to Lanyon Moor!" When play ends: say "And so the mists of Lanyon Moor close behind you." We can force play to end at any point, by using one of the following phrases inside some rule: end the story; end the story finally; end the story saying "Finis"; end the story finally saying "You have won"; When play ends, we may resume after all, if we wish: When play ends: say "Here, try again..."; resume the story. 2. Scoring. Not all works of interactive fiction require a scoring system. If we do not want scoring at all, the sentence Use no scoring. will prevent score commands from being understood. Otherwise, we may bump up (or down) the player's score with phrases such as: increase the score by 10 points; decrease the score by 5 points; If we want to associate ranks automatically with different score levels, we may do so by providing a special table: Table of Rankings Score Rank 0 "Rank Amateur" ... 3. Every turn. We may define instructions to occur once per turn with an every turn rule, like this: Every turn, say "The thirteen clocks ominously decline to tick." Every turn when the player is in the Kitchen: say "The dripping of the faucet continues to annoy you." These rules may or may not print anything, and can be used to accomplish all sorts of effects, from atmospheric events to independent behavior by other characters. 4. Time of day. By default, Inform keeps track of the time of day, according to a standard 24-hour system, in which time progresses at a rate of one minute per move. (See the Recipe Book for examples of how to change the rate of time, or to abolish 24-hour time and replace it with something else entirely.) Unless we say otherwise, a game is understood to begin at 9:00 AM. If we wish to change this, we may include an assertion such as The time of day is 10:00 AM. Like all assertions, this describes the situation at the start of play: once the game gets going, time will of course roll onward. We may print out the time of day with such phrases as say "[the time of day]"; say "[the time of day in words]"; say "[the time of day to the nearest five minutes in words]"; We may also perform calculations and change the current time, as in: increase the time of day by 2 hours; let N be the minutes part of the time of day; say "[10 hours after the time of day]"; Instead of sleeping: say "You doze fitfully, then wake with a start to see daylight."; now the time of day is 11:15 AM. 5. Scheduling future events. We have two ways to schedule events. One is to write a rule which takes place at a specific time of day: At 4 PM: say "The great bells of the clock tower chime four." The other is to create a rule starting with "When...", which will not take place until a named event happens: At the time when the egg-timer clucks: say "Sqwaaark!" Here "the egg-timer clucks" is the event. It may never happen: the only way it will occur is if a phrase in some other rule specifies when - the egg-timer clucks in four turns from now; 6. Talking about past events. Finally, we are allowed to write conditions about things the player is doing or has done, as in if taking a container, ... (currently) if we have taken the lantern, ... (ever) if the player is in the Hall, ... (currently) if the player is in the Hall for the third time, ... (currently, but referring to past trips) if the player has been in the hall for 3 turns, ... (continuously) if the gate was open, ... (at the start of this action) if the gate has been open, ... (at any time) if the gate had been open, ... (as of the start of this action) Chapter 10: Scenes 10.1. Introduction to scenes As we have seen, Inform divides up space into individual places called "rooms", and allows us to group rooms together into "regions" if we find that convenient. And Inform also divides time up, into individual turns. These too we can group together: the equivalent of a region is a "scene". To put this another way, if we think of the interactive fiction as a stage play, then up to now it has simply contained endless dialogue and stage directions - there has been no convenient way to divide up its running time into dramatic episodes, in the same way that a playwright might make Act II take place in the same drawing-room as Act I, but (let us say) six months later, after many things have changed. The script contains cues for one scene to end and another to begin: when those cues are reached, the stage hands rearrange props, actors reposition themselves and so on. Inform also allows us to create scenes, with cues for them to start and end, and some stage machinery (so to speak) making it easy to move the action on. But interactive fiction is interactive, so the metaphor of the theatre only goes so far. We can have several different scenes going on at once - perhaps with the relevant events taking place in different rooms, which the player is free to walk between. And the player may make a choice which changes the story-line, causing scenes to happen which otherwise would not have happened, and so on. Scenes can even be "recurring", that is, can repeat themselves. So organising the story-line into scenes is not simply a matter of making a list (Scene 1, then Scene 2, then Scene 3, finis). It is more like a chart in which one scene can lead in several possible ways to others - a sort of map of time, which as we shall see Inform displays in its "Scenes" index. 10.2. Creating a scene As usual, we only need to say that something is a scene to make it so: Train Stop is a scene. We conventionally write scene names with capital letters, as this demonstrates. This works, and shows up in the "Scenes" index, but does nothing. We have given no instructions on when it begins - no cue, in stage-play terms - so it never will begin, and even if it did, nobody would notice since it does nothing. First, to give it a beginning: Train Stop begins when the player is in the Station for the third turn. In theory any condition can be used to cue the scene - here, it's "the player is in the Station for the third turn" - but it's wise to look for a state of affairs which will last at least a brief time, because scene changes only happen at the start and end of turns. (Something like "...when examining the timetable" may be true only for a part of the middle of a turn, and so go unnoticed.) Every scene has two rulebooks attached, one at each end, so to speak. These look very like "when play begins" and "when play ends", and work in the same way. Thus: When Train Stop begins: move the Flying Scotsman to the Station; say "The Flying Scotsman pulls up at the platform, to a billow of steam and hammering." When Train Stop ends: remove the Flying Scotsman from play; if the player is in the Station, say "The Flying Scotsman inches away, with a squeal of released brakes, gathering speed invincibly until it disappears around the hill. All is abruptly still once more." Thus when the scene begins, our imaginary stage-hands wheel in a steam train; when it ends, they get rid of it again. Note that we know where the player will be at the start of the scene, but by the end he may have wandered off across the fields, so we must be careful not to report something he might not be in a position to see. When Train Stop begins, we printed some text, but we did this by hand. We didn't need to, because Inform automatically prints out the description of a scene (if it has one) when the scene begins. Scenes can have properties, just like objects, and in particular they have the "description" property. For example, we could write: Arrival is a scene. "There's a flourish of trumpets." which saves us the trouble of writing the rule: When Arrival begins: say "There's a flourish of trumpets." We can also write rules like this which apply to a whole variety of scenes at once. For instance: A scene can be bright or dim. A scene is usually dim. Dawn is a bright scene. When a scene which is bright ends: say "So passes the bright [scene being changed]." Here, instead of naming a scene ("Train Stop"), we've given a description ("a scene which is bright"). Example 154 (*): Pine 1 Pine: Using a scene to watch for the solution of a puzzle, however arrived-at by the player. Example 155 (**): Entrapment A scene in which the player is allowed to explore as much as he likes, but another character strolls in as soon as he has gotten himself into an awkward or embarrassing situation. 10.3. Using the Scene index But when we test the previous section's example, we find that after a brief wait, the train pulls up: but it never goes away again. We have given instructions on how the scene ends, but not when it ends, and as a result the scene goes on forever once started. Even with simple story-lines, and this one could hardly be simpler, it is surprisingly easy to overlook something so that the whole story-line is derailed. The Scene index is intended to help with this. At the top is a chart showing all the scenes and how they are to begin, along with a key to the symbols used on it. One scene always included is "Entire Game", a special scene which, as its name implies, is always being played out. But if we look at the Scene index for the previous example, we will also see our Train Stop scene, and find that it is marked with the red warning symbol for "never ends". Let us fix this: Train Stop ends when the time since Train Stop began is 3 minutes. Note the useful value "time since Train Stop began":

time since (scene) began ... time
This phrase produces the time since the named scene began, which only makes sense, of course, if it has indeed begun. Example: time since Entire Game began

time since (scene) ended ... time
This phrase produces the time since the named scene ended, which only makes sense, of course, if it has indeed ended. Example: time since Formal Dinner ended
The actual times, in case they are needed, can be obtained with:

time when (scene) began ... time
This phrase produces the time (i.e., the value of the "time of day" variable) at the moment when the given scene began.

time when (scene) ended ... time
This phrase produces the time (i.e., the value of the "time of day" variable) at the moment when the given scene ended.
(Testing command) The testing command SCENES causes Inform to monitor the beginning and ending of scenes, and report on them. For instance: >ask monk about lodging "Welcome a poor traveler for the night?" you ask, rubbing your fingers together to restore a little feeling. The monk looks you up and down for a moment and you sense his reaction hanging in the balance; then he slaps you on the back, hard enough to drive the air from your lungs. "In." [Scene 'Greeting' ends] The monk takes your elbow and pushes you imperiously toward dinner. [Scene 'Banquet' begins] Example 156 (*): Age of Steam The railway-station examples so far put together into a short game called "Age of Steam". 10.4. During scenes Scenes are not only useful for changing the setting, by moving items or people around and providing a little narration. We can also make the rules different in one scene from another. For instance, at a sleepy country halt there is no reason why one should not walk across the tracks: but if there is a train in the way, that would be impossible. Before going north during the Train Stop, say "The train blocks your way." instead. Any rule can have the clause "during ..." attached, provided that clause goes at the end and explicitly names a scene. This is especially useful with "every turn": Every turn during the Train Stop, say "Water is sluiced out of the tank and into the engine." We can test whether a scene is happening with the adjective "happening": if Train Stop is happening, ...

if (scene) has happened:
This condition is true if the given scene has both begun and ended.

if (scene) has not happened:
This condition is true if the given scene has not ended (or never started).

if (scene) has ended:
This condition is true if the given scene ended at least once.

if (scene) has not ended:
This condition is true if the given scene has never ended.
We need to be a bit careful: it's possible to set things up so that the Train Stop scene will play out more than once, so "Train Stop is happening" and "Train Stop has happened" might both be true at once. The kind of value "scene" is one which is allowed to have properties - it has a tick in the "properties" column in the chart on the Kinds index page - and this can be very useful in describing scenes. For instance, we could write: A scene can be thrilling or dull. Train Stop is dull. A scene has a text called cue speech. The cue speech of Train Stop is "All aboard!". Inform has the adjectives "recurring", "non-recurring" and "happening" all built in to describe scenes, and the above would add "thrilling" and "dull". Moreover, the "during" clause of a rule can give a description of a scene as easily as a specific scene name. For instance: Before going north during a dull non-recurring scene, ... Example 157 (*): Full Moon Random atmospheric events which last the duration of a scene. Example 158 (**): Space Patrol - Stranded on Jupiter! We'll be back in just a moment, with more exciting adventures of the... Space Patrol! Example 159 (***): Day One A scene which plays through a series of events in order, then ends when the list of events is exhausted. Example 160 (***): Bowler Hats and Baby Geese Creating a category of scenes that restrict the player's behavior. 10.5. Linking scenes together Let us suppose that somebody gets off the train, after all, so that a second scene follows on. Brief Encounter is a scene. Brief Encounter begins when Train Stop ends. The effect of this is that they occur in sequence. If we add a third to the chain of scenes: Village Exploration is a scene. Village Exploration begins when Brief Encounter ends. ...we find another chance to fool ourselves: if we check the Scenes index again, we can see the linkages between these scenes, but we also see that Brief Encounter never ends (despite its name). All we have said is that another scene begins where Brief Encounter leaves off, but it never does, so this is moot. Example 161 (***): Pine 2 Pine: Adding a conversation with the princess, in which a basic set of facts must be covered before the scene is allowed to end. 10.6. More general linkages We are allowed to link the beginning or end of any scene to the beginning or end of any other scene. So, for instance: Luggage Trouble is a scene. Luggage Trouble begins when Brief Encounter begins. Thus the two scenes run concurrently, at least for a while. We can also add that: Luggage Trouble ends when Brief Encounter ends. This can be useful when a large, complicated scene really contains several smaller sub-scenes. A special exceptional case is that we can have any scene or scenes starting right at the outset: Railway Meeting is a scene. Railway Meeting begins when play begins. When play ends, of course, all scenes end, so there is no need to say that. Example 162 (*): The Prague Job Scenes used to provide pacing while the player goes through his possessions. Example 163 (***): Entrevaux Organizing the game by scenes, where each scene has a location and prop lists so that it can be set up automatically. 10.7. Multiple beginnings and repeats It is quite allowed for a scene to be linked to several other scenes, and this is useful if several alternate strands of plot are being brought together in a common resolution scene: Bittersweet Ending begins when Stranger's Rejection ends. Bittersweet Ending begins when Stranger's Acceptance ends. and we can also have the same scene beginning when a condition holds. In general, it will begin the first time it gets any chance to do so. All scenes are ordinarily set up so that they can happen only once. But sometimes we want them to repeat. Suppose the train calls not once only, but every twenty minutes. We could set this up with two scenes linked back to back like so: Train Stop is a recurring scene. Train Wait is a recurring scene. Train Wait begins when play begins. Train Stop begins when Train Wait ends. Train Wait begins when Train Stop ends. The difference here is that these scenes have been declared as "recurring". In all other respects they are the same as any other scene. Example 164 (*): Night and Day Cycling through a sequence of scenes to represent day and night following one another during a game. Example 165 (***): Pine 3 Pine: Allowing the player to visit aspects of the past in memory and describe these events to the princess, as a break from the marriage-proposal scene. 10.8. Multiple endings Interactive fictions vary considerably in the extent to which the player is allowed to influence the story-line. Sometimes the appearance of making choices is wholly bogus, as only one possible line is given more than lip service. But in other works, the player can radically change the outcome, and whole rafts of plot differ between one person's experience and another's. Inform allows multiple endings to its scenes to make this kind of branching story-line easy to achieve. Any scene can have up to 8 alternate endings, differentiated by name. These are created as and when conditions are set for them: Brief Encounter ends happily when ... Brief Encounter ends wisely but sadly when ... "Ends happily" and "ends wisely but sadly" behave just like "ends". We can have rules "When Brief Encounter ends happily, ..." and so forth, in addition to rules "When Brief Encounter ends, ..." - if a rule doesn't specify any particular ending, it applies to all of them. We can also link rules together from these branches, so Stranger's Acceptance begins when Brief Encounter ends happily. Stranger's Rejection begins when Brief Encounter ends wisely but sadly. With this set-up and that of the previous section, there are now two possible paths through the story: (i) Train Stop - Brief Encounter - Stranger's Acceptance - Bittersweet Ending (ii) Train Stop - Brief Encounter - Stranger's Rejection - Bittersweet Ending We might later need to know which of these paths has been taken, and to help with this Inform provides conditions like so: if Brief Encounter ended happily ... if Brief Encounter did not end happily ... if Brief Encounter ended wisely but sadly ... if Brief Encounter did not end wisely but sadly ... (For a scene which repeats, note that these conditions apply only to the most recent repetition: and that such conditions are always false if the scene is currently going on. "Brief Encounter did not end happily" will be true only when the scene has finished but in a different way.) Example 166 (***): Panache Replacing the score with a plot summary that records the events of the plot, scene by scene. Example 167 (***): Pine 4 Pine: Adding a flashback scene that, instead of repeating endlessly, repeats only until the Princess has understood the point. 10.9. Why are scenes designed this way? In the part it plays in stories, time is like space. The endings of a scene (along with its beginning) are like the map connections leading out of a room. The Scenes index keeps track of the "map of time" through which these possible story-lines traverse. Some works of IF will have immensely complicated story-lines in only a few rooms, some will have no scenes at all despite a sprawling geography. The Scenes and World index tabs, side by side, show both kinds of map. Just as Inform uses a simple but practical design for the boundaries between rooms (map connections and doors, that is), it also simplifies transitions between scenes. Scenes are based on states of things: we give circumstances for them to begin or end. There is no phrase with the power to say "make Act II begin right now", so perhaps it is worth explaining why not. The state-based approach was chosen because: * it guarantees that each action falls entirely inside, or entirely outside, of any given scene (and therefore that "during..." clauses in the conditions for a rule are not affected by rule ordering); * it ensures that scene changes occur outside actions, like every turn rules; * it promotes a style of writing which makes it clearer to the reader of the source text when a scene begins and ends, and what conditions are guaranteed to be true during it; * it makes it possible for the Scenes index page to show this information in a communicative way. Settings in IF where one revisits the same location but at a different time, or after a dramatic change, have historically been difficult to test properly and prone to mistakes. (The classic example would be where a character killed during Act I reappears unharmed in Act II.) The design of scenes is an attempt to encourage a style of writing which minimises the risk of these accidents. Since scenes are, in the end, only a convenient way to organise rules, and do nothing that cannot be done by other means, this simplified system of scene changing does not really restrict us. 10.10. Review of Chapter 10: Scenes 1. A scene is a stretch of time somewhere in our narrative. We might choose to use scenes to organize the entire structure of our plot; just for timed or occasional events; or not at all, as we prefer. Scenes are a flexible way to keep an eye on and react to complex aspects of the world state, so they might for instance be used to monitor whether or not puzzles have been completed, determine when it is time to move the player to a new location, provide background activity, and so on. 2. We define a new scene with Train Stop is a scene. A scene has only a single beginning but is allowed to have many different named endings. We indicate how our scenes are to begin and end like so: Train Stop begins when ... Train Stop ends when ... Duel to the Death ends tragically when ... These need not be simple rules. If necessary, long wordy conditions can be given: or, using techniques from the chapter on phrases, we could define a phrase to make a really complicated decision. Scenes cannot be begun or ended just by saying so, using "now". Although the condition "the Horrible Argument is happening" correctly tests for whether this scene is under way, demands like "now the Horrible Argument is happening" or "now the Duel to the Death has ended" are not allowed - scenes begin and end only when the conditions are met. There are several reasons for this, but one is that it makes it possible for the Scene Index to keep track of how scenes fit together in the course of our story. 3. Just as rooms are joined together by map connections, we can join scenes together so that they lead one into another or run in parallel: Passenger Throng ends when Train Stop ends. Train Departure begins when Train Stop ends. Train Departure ends when Nightfall begins. Owl Screeching begins when Nightfall begins. Or we can say that a scene begins "when play begins". 4. We can write rules applying during the scene like so: Every turn during Train Stop: ... Before taking the luggage during Train Stop: ... After listening when Train Stop is happening: ... Instead of going to the Outdoor Region during Train Stop: ... We may also check afterward whether a scene has happened: Instead of kissing Miss Tilford when Train Stop has happened: ... "The Waiting Room is freshly painted.[if Train Stop has ended] But it somehow seems desolate now." and so on. For instance, we could use such conditions to assemble a summary of the plot so far for the player. 5. More than one scene can be happening at the same time, so it is not sensible to talk about "the current scene", in the way that we talk about the location of the player. The player can only be in one room at a time, but he can be in the midst of multiple scenes (or none). Example 168 (***): Cheese-makers Scenes used to control the way a character reacts to conversation and comments, using a TALK TO command. Chapter 11: Phrases 11.1. What are phrases? Phrases are instructions to Inform to do something, or to decide whether something is true or false, or to produce a value, or to say something. Inform has around 350 phrases built-in, and the chapters so far have already defined about 100 of those. In this chapter we'll see some key phrases for organising instructions of what to do, and also see how to define entirely new phrases. Just to run through the four sorts of phrase with examples: (a) Phrases to do something. These are the ones used in the body of a rule. For example, When Train Stop begins: move the Flying Scotsman to the Station; say "The Flying Scotsman pulls up at the platform." Rules like this begin with a "preamble", the beginning part which tells Inform when or how they apply, and then follow on with a list of instructions - here, just two of them. "move ... to ..." and "say ..." are both phrases. Inform provides about 130 of these built-in. It's actually not quite true that they all do something, because one of them is:

do nothing
This phrase does nothing at all. It is very occasionally useful to make a rule which does nothing: This is the largely ineffective rule: do nothing.
(b) Phrases to decide whether a condition is true. These are the ones which can be used in an "if": if action requires light: ... Not all conditions come from phrases. For example, "if the front door is closed" and "if Peter is wearing the sandals" have meanings which come from the verbs "to be" and "to wear". Inform provides about 60 built-in conditions, which give a friendly wording for questions which would be lengthy or difficult to write in any other way. (c) Phrases to decide a value. For example: square root of 16 produces a number, 4 of course, and can be used whenever a number is expected. Inform provides about 100 built-in phrases like this. (d) Text substitutions. These are actually just phrases whose definition begins with "To say ...". Example: "It's now [time of day in words]." Inform provides about 60 built-in text substitutions. 11.2. The phrasebook The Phrasebook is Inform's collection of recognised phrases, and it can always be browsed using the Index panel of the same name. Even the smallest project has a good-sized phrasebook, since it contains all of the built-in phrases. But most projects also define new phrases of their own. Here is a simple definition of a new phrase: To spring the trap: say "'Sproing!' go the hinges and, with a flash of silver, the enormous blades whisk together!"; end the story. Inform allows us to use whatever conventions of layout we prefer, but it's customary to use indentation like this, dividing off the preamble from the phrases which follow. As can be seen, definitions of new phrases look very like rules. What makes this definition a simple one is that the wording is fixed. The only way to use this would be from another phrase or rule, like so: Instead of entering the cage: spring the trap. In the next section we'll see how to give more complicated definitions which, like "move ... to ...", allow for the wording to change with the circumstances. 11.3. Pattern matching In this section, let's take the built-in phrase "remove ... from play" as an example. As the wording suggests, this causes whatever thing is named to disappear from every room, going into a sort of off-stage limbo. Although the wording can be different each time this is used: remove the diamonds from play; remove Mr Cogito from play; remove the honey sandwich from play; ... a single definition in Inform's Standard Rules nevertheless covers all of these possibilities. It is written like so: To remove (item - an object) from play: ... The bracketed part of the definition tells Inform to expect an object in that position, and Inform enforces this carefully. So this definition might tell Inform what "remove the barricade from play" means, but not what remove "blue cheese" from play; remove 63 from play; mean. Unless some other definition sorts the matter out, Inform will reply to uses like this with a Problem message: Problem. You wrote 'remove 63 from play' (Image Reveal.png here), but '63' has the wrong kind of value: a number rather than an object. The object does not need to be named literally, but can be anything which works out to be an object: for instance, After dropping something in the Nebulous Mist: remove the noun from play. which Inform allows because "noun", here, is a name for the object which is being acted on. Inform decides which definition to apply in a process called "pattern matching". The bracketed part of the example definition has the form "(name - kind)". The definition only applies if the text supplied agrees with the "kind" part - for instance, the diamonds agreed with "object", but 63 did not. If the definition does apply, then the Inform works through the rest of the phrase using "name" to mean whatever value matched. For example: To slam shut (box - an open container): say "With great panache, you slam shut [the box]."; now the box is closed. When this phrase is followed, "box" means whatever open container the pattern-matcher found when it was called for. For example, if Inform reads slam shut the Dutch armoire; then it acts on this by following the definition of "slam shut ...", using the Dutch armoire object as the value of "box", so it prints: With great panache, you slam shut the Dutch armoire. and renders it closed. In fact any description can be given in the definition, and that includes a single, specific value. For instance, we could define: To grant (bonus - a number) points: increase the score by the bonus. To grant (bonus - 7) points: say "You shiver uncontrollably." which would withhold this unlucky bounty. That would mean that: grant 7 points; grant seven points; would each produce uncontrollable shivers, because Inform uses the definition applying to the number 7; but grant six points; would increase the score by 6. In general Inform always follows the principle that more specific definitions take priority over more general ones. So although the definitions: To grant (bonus - a number) points: ... To grant (bonus - 7) points: ... both apply to the case of "grant 7 points", Inform uses the second, because it's the more specific of the two possibilities. Sometimes it will not be possible to tell if the value supplied meets the requirements until the game is actually playing. If, at run-time, no definition fits some phrase which has to be carried out, a run-time problem message is produced. Finally, and more straightforwardly, we can specify variations in wording using slashes between alternative words in a "To ..." definition. For instance: To grant (bonus - a number) point/points: ... allows the final word to be either "point" or "points". Slashes like this can only be used with literal words, not bracketed values, and give alternative forms only of a single word at a time. (If we need more variation than that, we should make more than one definition.) Example 169 (*): Ahem Writing a phrase, with several variant forms, whose function is to follow a rule several times. Example 170 (**): Ferragamo Again Using the same phrase to produce different results with different characters. 11.4. The showme phrase We've already seen the SHOWME command, which can be typed into the Game panel to look at the state of something, usually a thing or room. SHOWME is a testing command which has no effect once the work is released; eventual players can't use it. Inform also has a phrase called "showme", which works in much the same way:

showme (value)
This phrase is intended for testing purposes only. If used in a story file running inside the Inform application, it prints a line of text showing the given value and its kind; in a Released story file, it does nothing at all. Example: When play begins: showme 11. produces number: 11 More usefully: Every turn: showme the score. Now, every turn, we get a line in the story's transcript like so: "score" = number: 0 Inform uses the quotation marks and equals sign to show that it had to do some work to find the answer. "score" wasn't a constant value - it was a variable, and Inform had to look up the current value.
"showme" is a convenient way to see what's going on inside a phrase which isn't behaving as expected, or to find out the kind of a value. Here are some trickier examples. Suppose our design includes: The matching key of the blue door is the brass Yale key. If we then try this: When play begins: showme matching key of the blue door. we get, when the story starts up, "matching key of the blue door" = object: brass Yale key Why is this an "object", when we know that the key is actually a "thing"? After all, if we "showme key" instead, we get: thing: brass Yale key The answer is a little technical: it's because Inform guarantees that the matching key is always an object, but not that it's always a thing - it just happens to be a thing at the moment. There's not really a contradiction, because a "thing" is a kind of "object", so in fact the key is both. If we try "showme matching key", we get something like this: objects valued property: property 23 which is even more technical - people never need to print the names of abstract property names during play, so Inform doesn't provide any good way of doing it. It is reduced to printing out an internal ID number ("property 23") instead of the name ("matching key"). This can't be helped: "showme" is a way to lift the lid and see what's going on inside Inform's machinery, and some of the corners are dark. All the same, "showme" can be very useful in tinkering with rules to make them work properly. It prints nothing at all in a Release version of a project, so it's impossible for these private notes to be shown accidentally to our eventual readers. 11.5. Conditions and questions A variety of "conditions" have already appeared in this documentation. A condition is a phrase which describes a situation which might be true, or might be false, and examples might include: Mr Kite is in Bishopsgate the score is greater than 10 Sherlock Holmes suspects a woman These are all examples of sentences, formed by putting nouns either side of a verb, and clearly a wide range of conditions can be written this way. But there are also a few special conditions built into Inform which have a fixed wording, and test questions difficult to address with ordinary sentences. For instance:

if in darkness:
This condition is true if the player currently has no light to see by. Note that the test is more complicated than simply testing if the player is in a dark room, ... since the player might have a torch, or be inside a cage which is itself in a dark room, and so on.
Another example of a condition not easily written as a sentence is:

if player consents:
This condition is unusual in doing something and not simply making a silent check: it waits for the player to type YES (or Y) or NO (or N) at the keyboard, and then is true if the answer was yes. Example: say "Are you quite sure you want to kiss the Queen? "; if the player consents: ...
Whether it's put to the player like this or not, testing a condition is really asking a question, and there is always a yes/no answer. In Inform this answer is not usually a value (unlike in some other computer programming languages), but it can be made into one. Firstly, we need a special kind of value to hold answers like this. It's called "truth state", and it has just two possible values, written as "true" and "false". We then need:

whether or not (a condition) ... truth state
This phrase converts a condition into its result as a value, which is always either "true" or "false". Example: whether or not 20 is an odd number produces the truth state "false". This is mostly useful for storing up results to look at later: let victory be whether or not all the treasures are in the cabinet; and then subsequently: if victory is true, ...
As another example, in most stories this: When play begins: showme whether or not in darkness. ...will produce a line: "whether or not in darkness" = truth state: false In short, "truth state" is a kind of value like any other. That means it can be the kind of a variable: Salvation earned is a truth state that varies. and it can similarly be used in table columns, lists, or anywhere else where values are allowed. Example 171 (**): Proposal Asking the player a yes/no question which he must answer, and another which he may answer or not as he chooses. 11.6. If Inform's most powerful phrases are those which control the others, making them repeat, or be skipped.

if (a condition) , (a phrase)
or: if (a condition):
This phrase causes the single phrase, or block of phrases, following it to be obeyed only if the condition is true. (If the condition must contain a comma for some reason, the block form should be used.) Example: if the red door is open, say "You could try going east?"
The sense of an "if" can be reversed by using the word "unless" instead:

unless (a condition) , (a phrase)
or: unless (a condition):
This phrase causes the single phrase, or block of phrases, following it to be obeyed only if the condition is false. (If the condition must contain a comma for some reason, the block form should be used.) Example: unless the red door is closed, say "You could try going east?"
"Unless" is clearly unnecessary, but it can be a good way to make the source text easier for humans to read. As we have seen, there are many different forms of condition in Inform. They usually take a form quite like an assertion sentence, except that they're questions and not statements of fact. For example: if the score is 10, ... if all of the people are in the Atrium, ... Questions like this are checked by Inform to see if they make sense. The following doesn't, for instance: if 10 is a door, say "Huzzah!"; This produces the baffled reply: Problem. In the line 'if 10 is a door, say "Huzzah!"' (Image Reveal.png here), I can't determine whether or not '10 is a door', because it seems to ask if a number is some sort of door. (Beta release note) Previous builds allowed the form:

if (a condition) then (a phrase)
This phrase is now deprecated and is exactly equivalent to: if (a condition), (a phrase) Use a comma instead of "then", or else use a block.
11.7. Begin and end In practice it is not enough to apply "if" to a single phrase alone: we want to give a whole list of phrases to be followed repeatedly, or to be followed only if a condition holds. We do this by grouping them together, and there are two ways to do this. One is as follows: To comment upon (whatever - a thing): if whatever is transparent, say "I see right through this!"; if whatever is an open door: say "Oh look, an open door!"; if whatever is openable, say "But you could always shut it." Here we group two phrases together under the same "if". Note that the "then" has been replaced by a colon, and that the indentation in the list of phrases shows how they are grouped together. In the example above, the source moves two tabs in from the margin; the maximum allowed is 25. Indentation is the convention used in this manual and in the examples, but not everybody likes this Pythonesque syntax. So Inform also recognises a more explicit form, in which the beginning and ending are marked with the words "begin" and "end": To comment upon (whatever - a thing): if whatever is transparent, say "I see right through this!"; if whatever is an open door begin; say "Oh look, an open door!"; if whatever is openable, say "But you could always shut it."; end if. (Pythonesque because it's a style popularised by the programming language Python, named in turn after "Monty Python's Flying Circus".) Example 172 (*): Matreshka A SEARCH [room] action that will open every container the player can see, stopping only when there don't remain any that are closed, unlocked, and openable. Example 173 (*): Princess and the Pea The player is unable to sleep on a mattress (or stack of mattresses) because the bottom one has something uncomfortable under it. 11.8. Otherwise We often need code which does one thing in one circumstance, and another the rest of the time. We could do this like so: if N is 2: ... if N is not 2: ... but this is not very elegant, and besides, what if the action we take when N is 2 changes N so that it becomes something else? Instead we use "otherwise":

otherwise if (a condition)
or: otherwise unless (a condition)
or: otherwise (a phrase)
or: else if (a condition)
or: else unless (a condition)
or: else (a phrase)
This phrase can only be used as part of an "if ...:" or "unless: ...", and provides an alternative block of phrases to follow if the first block isn't followed. Example: if N is 2: ... otherwise: ... When there is only a single phrase we can use the shortened form: if N is 2, say "Hooray, N is 2!"; otherwise say "Boo, N is not 2..."; We can also supply an alternative condition: if N is 1: ... otherwise if N is 2: ... otherwise if N is greater than 4: ... At most one of the "..." clauses is ever reached - the first which works out.
If the chain of conditions being tried consists of checking the same value over and over, we can use a convenient abbreviated form:

if (word value) is:
This phrase switches between a variety of possible blocks of phrases to follow, depending on the value given. Example: if the dangerous item is: -- the electric hairbrush: say "Mind your head."; -- the silver spoon: say "Steer clear of the cutlery drawer." One alternative is allowed to be "otherwise", which is used only if none of the other cases apply, and which therefore guarantees that in any situation exactly one of the blocks will be followed. if N is: -- 1: say "1."; -- 2: say "2."; -- otherwise: say "Neither 1 nor 2.";
This form of "if" layout is not allowed to use "begin" and "end" instead of indentation: it would look too messy, and would scarcely be an abbreviation. It is also not allowed to use "unless" instead of "if", because the result would be too tangled to follow. Example 174 (*): Numberless A simple exercise in printing the names of random numbers, comparing the use of "otherwise if...", a switch statement, or a table-based alternative. 11.9. While The next control phrase is "while", which has the form:

while (a condition):
This phrase causes the block of phrases following it to be repeated over and over for as long the condition is true. If it isn't even true the first time, the block is skipped over and nothing happens. Example: while someone (called the victim) is in the Crypt: say "A bolt of lightning strikes [the victim]!"; now the victim is in the Afterlife;
We must be careful not to commit mistakes like the following: while eggs is eggs: say "again and "; which, as sure as eggs is eggs (which is very sure indeed), writes out again and again and again and again and again and ... forever. (Inform won't prevent this: we will find out the hard way when the game is played.) While we would probably never write anything so blatant as that, the mistake is all too easy to commit in disguised form. We should never design a loop, as repetitions like this are called, without worrying about if and when it will finish. As with "if", we can use "begin" and "end" instead of a tabulated layout if we want to -- while ... begin; ... end while. (The "begin" of an "if" must of course match an "end if", not an "end while", and so on.) (Beta release note) Previous builds allowed two other forms:

while (a condition) repeatedly (a phrase)
or: while (a condition) , (a phrase)
This phrase causes the single phrase following it to be repeated over and over for as long the condition is true. If it isn't even true the first time, nothing is done at all. These forms of "while" are now deprecated, and should be replaced by the standard block form: while (a condition): ...
Experience shows that it is much more legible to lay out "while" loops as blocks, even in these rare cases when only a single phrase forms the body of the block. 11.10. Repeat The other kind of loop in Inform is "repeat". The trouble with "while" is that it's not obvious at a glance when or whether the loop will finish, and nor is there any book-keeping to measure progress. A "repeat" loop is much more predictable, and is more or less certain to finish. There are several forms of "repeat", of which the simplest is similar to the old FOR/NEXT loop from the home-computer programming language BASIC, for those with long memories:

repeat with (a name not so far used) running from (arithmetic value) to (arithmetic value)
or: repeat with (a name not so far used) running from (enumerated value) to (enumerated value):
This phrase causes the block of phrases following it to be repeated once for each value in the given range, storing that value in the named variable. (The variable exists only temporarily, within the repetition.) Example: repeat with counter running from 1 to 10: ... This, and runs through the given phrases ten times. Within those phrases, a special value called "counter" has the value 1 the first time through, then the value 2, then 3 and so on up to 10. (It can of course be called whatever we like: this is only an example.) The range can be from any kind where ranges make sense - anything on which arithmetic can be done, so for instance repeat with moment running from 4 PM to 4:07 PM: ... and also any enumeration: Colour is a kind of value. The colours are red, orange, yellow, green, blue, indigo and violet. ... repeat with hue running from orange to indigo: ...
We are allowed to "nest" loops, that is, to put one inside another. To plot a grid with size (S - a number): repeat with x running from 1 to S: say "Row [x]:"; repeat with y running from 1 to S: say " [y]"; say "." If we then write plot a grid with size 5; then the result is Row 1: 1 2 3 4 5. Row 2: 1 2 3 4 5. Row 3: 1 2 3 4 5. Row 4: 1 2 3 4 5. Row 5: 1 2 3 4 5. Thus the innermost phrase, the say which mentions "y", happens 25 times. Whenever dealing with numbers in Inform we may need to remember that if the Settings for the project are set to use the Z-machine, the range is restricted to -32768 up to 32767. Repeating with a counter up to exactly 32767 is hazardous, because the counter can never break through this barrier: it's infinity, so far as Inform is concerned, and that can cause the repetitions to go on forever. (On Glulx, numbers can be very much larger.) Example 175 (*): Wonka's Revenge A lottery drum which redistributes the tickets inside whenever the player spins it. 11.11. Repeat running through Inform is not used very much for numerical work, so the kind of repeat loop described in the previous section is not much used. Inform's natural domain is really the world of things and rooms, so the following kind of repeat is much more useful.

repeat with (a name not so far used) running through (description of values):
This phrase causes the block of phrases following it to be repeated once for each value matching the description, storing that value in the named variable. (The variable exists only temporarily, within the repetition.) Example: repeat with item running through open containers: ... If there are no containers, or they are all closed, the phrases will not be followed at all. Inform will issue a Problem message if the range of the loop may be infinite: for example, it won't allow: repeat with X running through odd numbers: ... On the other hand it will allow: repeat with T running through times: ... which repeats 1440 times, starting with T at midnight and finishing at 11:59 PM. See the Kinds index for which kinds of value can be repeated through.
As with counting the "number of ..." objects satisfying some property, we can run through a wide variety of possibilities - any description whose range is possible for Inform to search. For example: repeat with dinner guest running through the people in the Dining Room: ... repeat with possession running through things carried: ... repeat with event running through non-recurring scenes which are happening: ... The following lists the whereabouts of all men in lighted rooms: repeat with suspect running through the men who are in a lighted room (called the scene): say "[The suspect] is in [the scene]."; Note the way we are allowed to give a name to the vaguely described place "lighted room", so that we can refer to it inside the loop. Example 176 (**): Strictly Ballroom People who select partners for dance lessons each turn. 11.12. Next and break So "repeat" and "while" phrases cause a block of other phrases to be repeated, over and over. The number of repetitions and the flow of "control" has so far been controlled only by the way the original loop was described. But in fact it's also possible to change this from inside the block being repeated, using these:

next
This phrase can only be used inside a "repeat" or "while" block, and causes the current repetition of the block to finish immediately. That either means the next repetition begins, or (if we are already at the last one) the loop ends too. Example: repeat with X running from 1 to 10: if X is 4, next; say "[X] ". produces the text "1 2 3 5 6 7 8 9 10 ", with no "4" because the "say" phrase was never reached on the fourth repetition.
In Monopoly terms, "next" is "Advance to Go" rather than "go directly, do not pass Go, do not collect $200" - the next iteration begins with the variable, if there is one, having cleanly moved on to the next value, just as if the loop had been run through in the normal way. ("Next" is called "continue" in a fair number of programming languages, so Inform issues a specific problem message to help people who forget this.)

break
This phrase can only be used inside a "repeat" or "while" block, and causes both the current repetition and the entire loop to finish immediately. Example: repeat with X running from 1 to 10: if X is 7, break; say "[X] ". produces the text "1 2 3 4 5 6 ", with nothing after "6" because the loop was broken at that point. The "say" wasn't reached on the 7th repetition, and the 8th, 9th and 10th never happened.
11.13. Stop Now that it's possible to define phrases where different things are done in different circumstances, we sometimes want to halt early. This is what "stop" is for.

stop
This phrase causes the current rule to end immediately. It is most often used in the definition of other phrases: To judge the score: if the score is 0, stop; say "The score is [score in words] more than it was a half-hour ago." In the case when the score is 0, the "stop" ends the phrase immediately, so that the subsequent text is printed only if the score is not 0. "Stop" can also be used in action rules, though this is not very good style - it's clearer to use "stop the action", which is exactly equivalent.
11.14. Phrase options There are sometimes several slightly different ways to perform a given task but which have substantially the same definition. In the following example: To go hiking, into the woods or up the mountain: if into the woods, say "Watch out for badgers."; if up the mountain, say "Better take your compass."; say "You go hiking." ...a phrase has been set up which can be used in three ways: go hiking; go hiking, into the woods; go hiking, up the mountain; Note that commas must be used to divide these "phrase options" from the rest of the text of the phrase. Within the definition of the phrase, the option's name is a valid condition, and if up the mountain, ... tests whether it is set; we can also test if it is not set using: if not up the mountain, ... A more substantial example from the Standard Rules is given by a phrase used mostly for internal, technical reasons:

list the contents of (object)
This phrase produces a list of all things whose holder is the given object, according to Inform's traditional conventions for room descriptions and inventory listings. Example: list the contents of Marley Wood, as a sentence, with newlines and including all contents; Where this is possible, it's generally better to use "[list of things in ...]" instead, which produces the same result in an acceptable way for the middle of a sentence.
Note that this phrase is allowed to have multiple options specified, whereas "go hiking" above was not: this is because it was defined thus: To list the contents of (something - an object), with newlines, indented, as a sentence, including contents, including all contents, giving inventory information, giving brief inventory information, using the definite article, listing marked items only, prefacing with is/are, not listing concealed items, suppressing all articles and/or with extra indentation: ... The significant difference is the word "and/or" instead of "or", which signals that more than one option can apply at a time. Example 177 (**): Equipment List Overview of all the phrase options associated with listing, and examples of how to change the inventory list into some other standard formats. 11.15. Let and temporary variables A variable, as we have seen, is a name for a value which changes, though always remaining of the same kind. For instance, if "target" is a number variable (or "number that varies") then it may change value from 2 to 4, but not from 2 to "fishknife". To make complicated decisions, phrases often need to remember values on a temporary basis. We have already seen this for the counter in a "repeat" loop, which exists only inside that loop, and then is no longer needed. We can also make temporary variables using "let":

let (a name not so far used) be (value)
or: let (a temporary named value) be (value)
This phrase creates a new temporary variable, starting it with the value supplied. The variable lasts only for the present block of phrases, which certainly means that it lasts only for the current rule. Examples: let outer bull be 25; let the current appearance be "reddish brown"; let the special room be Marley Wood; The kinds of these are deduced from the values given, so that, for instance, say "The outer bull scores [the outer bull in words] when you practice archery in [special room]." produces The outer bull scores twenty-five when you practice archery in Marley Wood. The variable name should be a new one; if it's the name of an existing one, then the kinds must agree. So: let outer bull be 25; let outer bull be 50; is a legal combination, because the second "let" simply changes the value of the existing "outer bull" variable to a different number.

let (a name not so far used) be (name of kind)
This phrase creates a new temporary variable of the given kind. The variable lasts only for the present block of phrases, which certainly means that it lasts only for the current rule. Example: let inner bull be a number; The variable created holding the default value for that kind - in this case, the number 0. A handful of very obscure kinds have no default values, and then a problem message is produced. Inform also disallows: let the conveyance be a vehicle; because temporary variables aren't allowed to have kinds more specific than "object". (This is a good thing: suppose there are no vehicles in the world?) It's quite safe in such cases to use let the conveyance be an object; instead, which creates it as the special object value "nothing".
Temporary variables made by "let" are only temporarily in existence while a phrase is being carried out. Their values often change: we could say let x be 10; now x is 11; for instance, or indeed we could "let x be 10" and then "let x be 11". But although we are allowed to change the value, we are not allowed to change the kind of value. The name "x" must always have the same kind of value throughout the phrase to which it belongs, so the following will not be allowed: let x be 45; now x is "Norway"; (The difference between using "let" and "now" here is that "let" can create a new temporary variable, whereas "now" can only alter things already existing: on the other hand, "now" can change many other things as well, whereas "let" applies only to temporary variables.) Example 178 (*): M. Melmoth's Duel Three basic ways to inject random or not-so-random variations into text. 11.16. New conditions, new adjectives We can create new conditions by defining a phrase with "to decide whether" (or equivalently "to decide if"): To decide whether danger lurks: if in darkness, decide yes; if the Control Room has been visited, decide no; decide yes. If the player is indeed in darkness, the decision is "yes" because the "decide yes" stops the process right there. We can now write, for instance, if danger lurks, ... In fact, "danger lurks" is now a condition as good as any other, and can be used wherever a condition would be given. Rules can apply only "when danger lurks", for instance.

yes
or: decide yes
This phrase can only be used in the definition of a phrase to decide whether a condition holds. It ends the decision process immediately and makes the condition true.

no
or: decide no
This phrase can only be used in the definition of a phrase to decide whether a condition holds. It ends the decision process immediately and makes the condition false.
We can also supply definitions of adjectives like this. So far, new adjectives have been defined like so: Definition: a supporter is occupied if it is described and something is on it. If we want to give a definition which involves more complex logic, we can use a special form allowing us to make arbitrary decisions. In this longer format, the same definition would look like so: Definition: a supporter is occupied: if it is undescribed, decide no; if something is on it, decide yes; decide no. Here "it" refers to the supporter in question. Note that there are now two colons in this sentence, one after "Definition", the other after the clause being defined. But that apart, it's a phrase like any other: it must end in "yes" or "no" just as the "danger lurks" example must. "Decide no" and "decide yes" are needed so often that they can be abbreviated by leaving out "decide": Definition: a supporter is occupied: if it is undescribed, no; if something is on it, yes; no. Example 179 (***): Owen's Law OUT always means "move to an outdoors room, or else to a room with more exits than this one has"; IN always means the opposite. 11.17. Phrases to decide other things A condition is a yes/no decision, but we can also take decisions where the result is a value. Suppose we want to create a concept of the "grand prize", which will have different values at different times in play. Each time the "grand prize" is referred to, Inform will have to decide what its value is, and the following tells Inform how to make that decision: To decide which treasure is the grand prize: if the Dark Room has been visited, decide on the silver bars; decide on the plover's egg. Note that we have to say what kind the answer will be: here it's a kind of thing called "treasure" (which we're supposing has already been created), and as it turns out only two treasures are ever eligible anyway (we're also supposing that the plover's egg and the silver bars are treasures already created, of course). And note also that the phrase must in all cases end with a "decide on ..." to say what the answer is:

decide on (value)
This phrase can only be used in the body of a definition of a phrase to decide a value. It causes the calculation to end immediately, with the outcome being the given value, which must be of the kind expected. Example: To decide which number is double (N - a number): let D be N times N; decide on D.
Now that we have "grand prize" created, we can use it just as we would use any other value, so for instance: if taking the grand prize, ... As this is something of a dialect difference between English speakers, "what" and "which" are synonymous here, i.e., we could equally well write something like: To decide what number is the target score: ... (A phrase to decide if something-or-other is exactly the same thing as a phrase to decide a truth state, and indeed, if we want to then we can use "decide on T", where T is a truth state, in its definition. For instance: To decide if time is short: if the time of day is after 10 PM, decide on true; ... decide on whether or not Jennifer is hurried. "Decide on true" is exactly equivalent to the more normally used "decide yes", and of course it is optional. The last line is more interesting since it effectively delegates the answer to another condition.) Example 180 (*): Witnessed 2 A piece of ghost-hunting equipment that responds depending on whether or not the meter is on and a ghost is visible or touchable from the current location. Example 181 (***): A Haughty Spirit Windows overlooking lower spaces which will prevent the player from climbing through if the lower space is too far below. 11.18. The value after and the value before A point which has come up several times in recent chapters is that enumerated kinds of value have a natural ordering. For example, if we write: Colour is a kind of value. The colours are red, orange, yellow, green, blue, indigo and violet. ...then we not only have seven possible values, we have put them into a sequence, in order of their naming. We can't perform arithmetic on colours, of course, but we can perform comparisons on them. Thus "red < yellow" is true, while "green >= violet" is not. (More on comparisons in the chapter on units, which also covers arithmetic.) It's also sometimes useful to get at the sequence directly. First, the two ends:

first value of (name of kind) ... value
This phrase produces the first-created value of the given kind, which should be an enumeration. Example: if we have Colour is a kind of value. The colours are red, orange, yellow, green, blue, indigo and violet. then "first value of colour" is red.

last value of (name of kind) ... value
This phrase produces the last-created value of the given kind, which should be an enumeration. Example: if we have Colour is a kind of value. The colours are red, orange, yellow, green, blue, indigo and violet. then "last value of colour" is violet.
And now how to step forward and back:

(name of kind) after (enumerated value) ... value
This phrase produces the next-created value of the given kind, which should be an enumeration. Example: if we have Colour is a kind of value. The colours are red, orange, yellow, green, blue, indigo and violet. then "colour after orange" is yellow.

(name of kind) before (enumerated value) ... value
This phrase produces the previous-created value of the given kind, which should be an enumeration. Example: if we have Colour is a kind of value. The colours are red, orange, yellow, green, blue, indigo and violet. then "colour before blue" is green.
Example 182 (*): Entropy All objects in the game have a heat, but if not kept insulated they will tend toward room temperature (and at a somewhat exaggerated rate). Example 183 (***): The Hang of Thursdays Turns take a quarter day each, and the game rotates through the days of the week. 11.19. Review of Chapter 11: Phrases 1. Phrases are what we use to make changes to the world or send messages to the player in an Inform game. They are active ("end the game") rather than merely descriptive ("a shaggy dog"). They only make sense if we know exactly in what circumstances they will happen. For instance, a paragraph in the source text which simply reads Say "Hello there!". is not allowed: when should this be said - when play begins? Every turn? If certain actions are tried? The source doesn't indicate, so this usage of a phrase is not allowed. Similarly, the following does not make sense: The tennis ball is carried by the player. If Fido can see the tennis ball, say "Fido barks at the tennis ball." Understand "green" or "toy" as the tennis ball. The "if..." phrase is one of the most useful, indicating that if a given condition holds, then then another phrase should take effect - in this case the condition is "Fido can see the tennis ball" and the other phrase tells the player that Fido barks. Again, though, we have not really said when all this happens: do we intend to check whether Fido can see the ball every turn? Or only in certain circumstances? So, just as with all other phrases, the "if..." phrase has to have a context: The tennis ball is carried by the player. Understand "green" or "toy" as the tennis ball. Every turn: If Fido can see the tennis ball, say "Fido barks at the tennis ball." Now it is clear that the condition and phrase are to be applied every turn, and the text works properly. Inform comes with numerous phrases built in, and the current stock can be seen in the Phrasebook Index of any project. Many phrases are needed only in special circumstances, but a few need to be in the repertoire of every Inform author: "if...", "say...", "now...", "while..." and "repeat...". 2. Phrases can be used in three circumstances: in rules, or to define new phrases in terms of simpler existing ones, or (for say phrases only) as substitutions in text. A rule is made up of a series of phrases, so that for instance in the following text Instead of washing the dog: say "You give the dog a good scrub."; move the sponge to the player; now the dog is sopping wet. "Instead of..." introduces a rule, which takes effect whenever the action "washing the dog" is tried. There are then three phrases ("say...", "move...", "change...") which take effect in succession. (Note the punctuation: the colon and then a list of phrases divided by semicolons.) 3. Inform defines a large number of phrases for us to use already, but we may sometimes need to create our own. A new phrase looks like a rule, but begins with "To" - it is a list of instructions saying how to do something. For instance: To reward persistence: increase the score by 5; say "Your persistence deserves a bonus. Keep up the good work." This creates a new phrase, "reward persistence", in terms of (in this case) two existing ones. We can then use "reward persistence" in other rules and new phrases. Other examples might be: To empty the player's luggage: ... To remove points from (character - a person): ... To remove (point value - a number) points from (character - a person): ... To make (character - a person) lose (point value - a number) points in the eyes of (voter - a person): ... Some phrases are complete in themselves, and have wording which never varies: for instance, the definition above means we would have to write exactly this - empty the player's luggage; - to achieve the emptying result. No variant is accepted: "empty Joe's luggage" does not match the definition, nor even "empty player's luggage", because even the "the" is compulsory. Alternatively, a phrase can require some additional input, in which case we must fill in the blanks of the phrase with specific values or names: remove points from James. remove 10 points from James. 4. Say phrases are those which begin with the word "say", and they can be used in one more circumstance: in square brackets as a text substitution. For instance, we might define To say Greek small letter beta: ... To say alphabet soup: ... To say age of (character - a person) in base six: ... As well as being used like any other phrase, these can also appear inside any text as a substitution. For instance: The printed name of the polystyrene beta is "giant polystyrene [Greek small letter beta] sign". Here there's no rule in sight, but Inform does not need one, because it knows exactly when this phrase takes effect - when the text is printed. Say phrases can also contain blanks to be filled in, so say "Joey is [age of the noun in base six]." would fill in the noun as "the character" in "To say age of (character - a person) in base six", determine the correct answer, and print it for the player. Because to say phrases can be arbitrarily complex, they are convenient ways to introduce random variations or bring in information about other aspects of the world. 5. Phrases to decide are different again. These phrases do not normally do something, but instead find something out. Examples include: To decide whether the cock has crowed: To decide whether (emperor - a man) rules wisely: To decide what number is the highest bid: To decide what number is the favourite number of (character - a person): To decide what colour is the prettiest colour: To decide what colour is the favourite colour of (character - a person): These phrases make no sense on their own and instead are used to fill out conditions or supply values for other phrases to use. For instance, it would make sense for a rule to include the phrase "say the highest bid" as one of its instructions, but "the highest bid" on its own would be like a rhetorical question. It mentions something without indicating what to do about it. The above examples might be used like so: if the cock has crowed, milk the cows. if Claudius rules wisely, deify Claudius. 6. Phrases are not always the most succinct way to teach Inform how to make decisions. Sometimes it is neater to define new adjectives (see Chapter 6). For instance To decide whether (jar - a container) is empty: ... has a very similar sense to Definition: a container is empty if... but the adjective defined in the second case can be used more flexibly. Both ways to introduce this idea will allow us to write if the vase is empty... but with the defined adjective we are also allowed to use "empty" in combination with nouns and other adjectives: Before taking the empty vase:... Instead of inserting something into an empty dirty vase:... In general, if we are contemplating a "to decide whether..." phrase about a single room or thing, it is more efficient to define an adjective instead. 7. Phrases which do something may also followed by a phrase option set off by commas. (Phrases to say are not allowed these, and they tend to lead to confusion if used in phrases to decide, although it is not strictly against the rules to try this.) Phrase options are useful if we have two very similar tasks to perform, which share most of the same instructions. Chapter 12: Advanced Actions 12.1. A recap of actions Actions are impulses to do something, which arise sometimes through typed commands: >examine tapestry and sometimes through "try" phrases occurring in other rules: Before examining the tapestry, try switching the ultraviolet light on. Every action either succeeds or fails, though failure may not be a bad thing (something better may have happened). Besides any rules applied in the source text, actions are subject to basic realism rules. A general rule ensures that actions are rejected if the actor would need to touch something which is out of reach, or see something which is invisible; and a couple of hundred other built-in rules police individual actions. For instance, if the ACTIONS testing command has been used to switch monitoring on, then: >unlock cage with watermelon [unlocking cage with watermelon] That doesn't seem to fit the lock. [unlocking cage with watermelon - failed the can't unlock without the correct key rule] Actions generated by "try" phrases are allowed to run "silently", which means that if nothing out of the way happens and they succeed, then nothing is printed. For instance: Before examining the tapestry: say "(Switching on the lamp first.)"; silently try switching the ultraviolet light on. There are many ways to impose extra rules on actions, and we have seen three main kinds: Before rules, intended so that preliminary activities like the one above can happen before the action is tried; Instead rules, which block or divert the intention, or may cause something spectacularly different to happen; and After rules, which allow for unexpected consequences after the action has taken place. 12.2. How actions are processed The following flow chart shows the natural course of events when Inform deals with a new action - a "taking" action in the case drawn. For quite a long time, the action may still fail, and it may be that nothing actually happens: but eventually a deciding line is crossed, and once that happens the action will certainly succeed. (Image achart.png here) The coloured boxes on this chart represent "rulebooks", that is, collections of rules with a common purpose. The orange boxes for Before, Instead and After were covered in the Basic Actions chapter, but the blue boxes are new. The orange boxes are where we put rules to handle unusual situations, or unexpected events: special rules to cover the opening of a container which happens to be booby-trapped, or walking through a doorway into a room where a surprise party is about to be sprung. Blue boxes hold the mundane, everyday rules - the generic ways that particular actions behave. Every action provides these: "Check" rules, to see if it makes sense - for instance, to see that the player is not trying to take his or her own body, or a whole room, or something he or she already has; then "Carry out" rules, to actually do what the action is supposed to do - in the case of taking, to move an object into the player's possession; and finally "Report" rules, which tell the player what has happened - perhaps printing up "Taken." When we create a new action, we add a new column to the blue rows in this diagram. As we shall see, we can also put new rules into the existing blue boxes: for instance, if we wanted to increase physical realism by forbidding the player to carry more than a certain weight, we would want to add a new "check taking" rule, and this is entirely legal. In subsequent chapters, we will see ways to intervene at almost every point in the above diagram - from how "Can we see or touch things?" is reckoned, to each and every individual rule in all of these books. Action-processing may be the single most important thing Inform does, so the system is designed to be immensely flexible. On the other hand, that does make it a lot to take in at one look. Newcomers should probably concentrate on "Instead" and "After" as the basic tools for designing the situations turning up routinely in interactive fiction. There are guidelines at the end of this chapter offering advice on which tricks to use when it comes to more complicated needs. 12.3. Giving instructions to other people So far, all actions have been carried out by the player: which is fine for exploring the passive world of an empty warehouse, but less good for a drama in which other characters have to be contended with. In fact, an action can be carried out by anybody - by any instance of the "person" kind, that is, which includes all the men, women and animals in the game, and not only the player. In interactive fiction, players conventionally ask other characters to do something with commands like so: > will, go west Clearly "will, go west" should not produce the same action as "go west", because a different person will be trying it: this person is called the "actor", and while the actor is ordinarily the player, here it is the character called Will. Inform distinguishes these two actions like so: going west asking Will to try going west As a result, we can write rules like so: Instead of asking Will to try going west, say "Will scratches his head, baffled by this talk of westward. Is not the ocean without bound?" To write rules like this, we sometimes want to generalise about who is supposed to do the deed. To do this we can refer to "person asked", just as the "noun" stands for whatever noun was typed: Instead of asking somebody to try taking something, say "I don't think we ought to tempt [the person asked] into theft, surely?" So if the player types "Algy, take sandwich", the "person asked" would be Algy; the "noun" would be the sandwich; and there would be no "second noun". Example 184 (*): Virtue Defining certain kinds of behavior as inappropriate, so that other characters will refuse indignantly to do any such thing. Example 185 (***): Latris Theon A person who can accept instructions to go to new destinations and move towards them according to the most reasonable path. 12.4. Persuasion "Asking ... to try ..." actions run through their Before and Instead rules like any other actions, but then (if no rule has intervened) something different happens: Inform has to decide whether the person asked consents to try the action or not. By default, the answer is always no, and text like the following will be printed: > will, go west Will has better things to do. However, we can intervene to make the answer "yes", using a special kind of rule which produces a yes/no answer. The following examples show how we can give broad or narrow permission, as we choose: Persuasion rule for asking people to try going: persuasion succeeds. Persuasion rule for asking Will to try going west: persuasion succeeds. Such a rule can either declare that "persuasion succeeds", or that "persuasion fails", or make no decision and leave it to another rule to say. If it decides that persuasion fails, it is also allowed to say something, describing why: in that event, the standard message ("Will has better things to do.") is suppressed. For example, Persuasion rule for asking Will to try going: say "Will looks put out, and mutters under his breath."; persuasion fails. The following rule, which is really only suitable for testing, makes everybody infinitely obliging: Persuasion rule for asking people to try doing something: persuasion succeeds. Supposing that Will does decide to cooperate, a new action is generated: Will going west and this is then subject to all of the usual action machinery. For instance, we could write a rule such as: Instead of Will going west, say "He runs out into the waves, but soon returns, rueful." So in this case the new action ("Will going west") failed: but the original action, "asking Will to try going west", is still deemed to have succeeded - after all, Will did try. To put it more formally, "asking X to try A" succeeds if the persuasion rules succeed, and otherwise fails. Note also that "Instead of..." rules written for other people will be treated by Inform as failures, even if we write something like Instead of Will pulling the cord: say "The bell rings." and thus may produce unsatisfactory results such as >WILL, PULL CORD The bell rings. Will is unable to do that. If we wish to write new successful actions for another character, we will need to create appropriate carry out and report rules for them: these will be explained in the sections to follow. (Finally, note that the mechanism Inform uses to see if we have printed a refusal message of our own, in the event of persuasion rules failing, can be fooled if we write a persuasion rule explicitly ending with a "[paragraph break]" text substitution.) Example 186 (*): The Hypnotist of Blois A hypnotist who can make people obedient and then set them free again. Example 187 (*): Police State Several friends who obey you; a policeman who doesn't (but who takes a dim view of certain kinds of antics). 12.5. Unsuccessful attempts Suppose, finally, that Will not only consents to try the action, but it also survives its passage through Before and Instead rules. What happens then? In principle, what happens to Will is exactly what would have happened to the player in his place. For instance: > will, go east Will leaves to the east. If on the other hand Will's attempt is frustrated because one of the checking rules stops him, then Will's action fails. For instance, if Will tries going northeast but there is no room to northeast, one of the rules checking the "going" action will stop him. We will then see this: > will, go northeast Will is unable to do that. This is rather a generic message, and we may want something more interesting. We can provide that using yet another special kind of rule: Unsuccessful attempt by Will going: say "Will blunders around going nowhere, as usual." Even that is still a little generic, though, because it treats all of the various ways that "going" can fail as the same. If we have ACTIONS switched on, we can see what goes on behind the scenes when we ask Will to walk into a door: >will, go west [asking Will to try going west] [(1) Will going west] [(1) Will going west - failed the can't go through closed doors rule] Will blunders around going nowhere, as usual. [asking Will to try going west - succeeded] (The "(1)" lets us know that a new action is starting during the old one, and before the old one finishes: sometimes we go up to three or four deep, though seldom more in practical cases.) We can now rewrite the "unsuccessful attempt" rule like so: Unsuccessful attempt by Will going: if the reason the action failed is the can't go through closed doors rule, say "Will looks doubtful and mumbles about doors."; otherwise say "Will blunders around going nowhere, as usual." The value "reason the action failed" is set to whichever checking rule threw out the action which Will tried. The names of these rules try to be self-explanatory - at any rate, those with gnomic names are not useful for this sort of thing, and can be ignored - and can be found out either using ACTIONS or by consulting the Actions index. Finally, note that "unsuccessful attempt" rules apply only when the person in question is being asked to perform the action by somebody else - as in the examples above. Example 188 (**): Generation X A person who goes along with the player's instructions, but reluctantly, and will get annoyed after too many repetitions of the same kind of unsuccessful command. 12.6. Spontaneous actions by other people The player's actions happen not only when he types a command, but can also happen spontaneously as a result of a "try" phrase. try going west try asking Will to try going west The latter might, of course, result in Will trying going west: or it might not - that depends on the persuasion rules. But as the author, we have the ultimate powers of persuasion, and can make Will act in any way we like, without asking: try Will going west Nobody in the simulated world requested this: it is an impulse felt by Will alone, so that - from the player's point of view - Will is acting spontaneously. The player need not be anywhere nearby, and may never know what happened. Recall that when actions work their way down through the flow-chart, they are stopped before reaching the "report" stage - when the player is told about them - if they are running "silently". This is also where Inform stops an action which is not witnessed by the player. To repeat a point in the previous section: "unsuccessful attempt" rules do not apply to actions which the author has caused to happen, using "try". When such actions fail, they invoke no special set of rules. Note that the text "try Will going west" involves the actor's name immediately placed next to the action he is to try, which in a very few cases might cause ambiguities. If the actor's name contains a participle like "going" - say, if Will's full name turned out to be Mr Will Going - then we would have to write out the action name in full, using "trying" to clarify matters: try Will Going trying going west Example 189 (*): IQ Test Introducing Ogg, a person who will unlock and open a container when the player tells him to get something inside. Example 190 (****): Boston Cream A fuller implementation of Ogg, giving him a motivation of his own and allowing him to react to the situation created by the player. 12.7. New actions It is not often that we need to create new actions, but a large work of interactive fiction with no novelty actions is a flavourless dish. Here we shall create an action for photographing things. The Ruins is a room. "You find this clearing in the rainforest oddly familiar." The camera is in the Ruins. "Your elephantine camera hangs from a convenient branch." Photographing is an action applying to one visible thing and requiring light. In theory that text is already sufficient to make the new action, but what we have so far is rudimentary to say the least. The two qualifications give Inform the useful information that we cannot photograph in the dark, and that we need to be photographing something - not, as in the case of waiting or taking inventory, acting without reference to any particular thing external to ourselves. The word "visible" here tells Inform that we do not need to be able to touch the thing in question: a line of sight is good enough. These two stipulations were necessary because the default arrangement is that any object must be in touching range, and that most actions can be performed in darkness. (Also, note that if you invent an action which needs to apply to directions like "north" or "south", you need to make this apply to visible things, because the object used inside Inform to represent the idea of "north" can be seen but not touched. So for understanding purposes, "visible thing" is understood as meaning any visible thing or direction: it's more general than "thing", not more specific.) Occasionally, when writing general rules about actions, it can be useful to find out what the current action's requirements are: the following conditions do what they suggest.

if action requires a touchable noun:
This condition is true if the action being processed is one whose (first) noun is an object which needs to be touchable by the actor. For example, it's true for "taking", but false for "examining".

if action requires a touchable second noun:
This condition is true if the action being processed is one whose second noun is an object which needs to be touchable by the actor. For example, it's true for "putting the brick in the sack", but false for "throwing the brick at the window".

if action requires a carried noun:
This condition is true if the action being processed is one whose (first) noun is an object which needs to be carried by the actor. For example, it's true for "dropping", but false for "taking".

if action requires a carried second noun:
This condition is true if the action being processed is one whose second noun is an object which needs to be carried by the actor.

if action requires light:
This condition is true if the action being processed is one which can only be performed if the actor has light to see by. For example, it's true for "examining", but false for "dropping".
As further examples, here we create "blinking" and "scraping X with Y". Note the use of "it" to indicate that the name of an object should go here. Blinking is an action applying to nothing. Scraping it with is an action applying to two things. The photographing action now exists, but with two provisos: (a) it never happens, because Inform does not know what commands by the player should cause it, and (b) even if it were to happen, nothing would follow, because Inform does not know what to do. (There are no check, carry out or report rules yet.) The first problem is easily overcome: Understand "photograph [something]" as photographing. We will return to the whole subject of parsing, as this process of understanding the player's commands is called, later. But this gives the gist of it. (See Understand for the full story.) Example 191 (*): Red Cross A DIAGNOSE command which allows the player to check on the health of someone. Example 192 (***): Frizz Liquid flows within containers and soaks objects that are not waterproof; any contact with a wet object can dampen our gloves. 12.8. Irregular English verbs Our three example actions can be recognised in play using the following: Understand "photograph [something]" as photographing. Understand "blink" as blinking. Understand "scrape [something] with [something]" as scraping it with. The last of these examples shows why Inform does not risk generating this automatically: English is so full of irregular verbs. Inform could have guessed "blink" and "photograph", but might then have opted for "scrap" instead of "scrape". Inform does risk automatically generating the past participle of an action. (Many past participles are never needed, so the stakes are lower if Inform gets this wrong.) What usually happens is that the "-ing" is replaced with "-ed", thus photographed, blinked, scraped - but Inform has a dictionary of some 460 irregular exceptions, such as caught, fled, crossbred, taken, woven. So with luck Inform will guess correctly. If not, we can get around this like so: Squicking is an action with past participle squacked, applying to one thing. Example 193 (***): 3 AM A shake command which agitates soda and makes items thump around in boxes. 12.9. Check, carry out, report The normal behaviour of an action is specified by its three associated rulebooks - check, carry out and report. In the case of our "photographing" example, these rulebooks will be: Check photographing. Here, for instance, we need to verify that the player has the camera. If any of our checks fail, we should say why and stop the action. If they succeed, we say nothing. Carry out photographing. At this stage no further checking is needed (or allowed): the action now definitively takes place. At this point we might, for instance, deduct one from the number of exposures left on the film in the camera, or award the player points for capturing something interesting for posterity. But we should say nothing. Report photographing. At this stage no further activity is needed (or allowed): whatever effect the action had, it has happened and is now over. All we can do is to say what has taken place. So far we have not really gone into the business of what rulebooks are, and we don't do so here either - suffice to say that we can now create whatever rules we need: A check photographing rule: if the camera is not carried: say "You can hardly photograph without a camera, now can you?" instead. In fact, writing "a check photographing rule" is over-formal. We can more simply label our rules like so: Check photographing: if we have photographed the noun: say "You've already snapped [the noun]." instead. Report photographing: say "Click!" For the sake of brevity, photography has no interesting consequence (no points to be won, no film to use up), so there are no carry out rules here. Note the way we used the word "instead" once again to stop actions in their tracks. We can continue to add rules at any point, and a classic thing that happens when testing a new work is that the designer realises there is a case which has not been thought of: Check photographing: if the noun is the camera: say "That would require some sort of contraption with mirrors." instead. Example 194 (*): The Dark Ages Revisited An electric light kind of device which becomes lit when switched on and dark when switched off. Example 195 (**): Paddington A CUT [something] WITH [something] command which acts differently on different types of objects. Example 196 (***): Delicious, Delicious Rocks Adding a "sanity-check" stage to decide whether an action makes any sense, which occurs before any before rules, implicit taking, or check rules. Example 197 (***): Noisemaking Creating a stage after the report stage of an action, during which other characters may observe and react. 12.10. Action variables For some complex situations, it can be useful to keep track of a few values throughout the processing of the action. This is not an everyday occurrence: in the Standard Rules, for instance, only two or three out of 90 actions need to do this. But suppose we want to write a more deluxe version of our "photographing" action. This time, rather than having a single thing called the "camera", we will provide a whole range of possible cameras, varying in quality: Photographing is an action applying to one visible thing and requiring light. Understand "photograph [something]" as photographing. The Studio is a room. Sally is a woman in the Studio. A foam-lined tote bag is in the Studio. A camera is a kind of thing. A camera has a number called picture quality. The digital SLR camera is a camera in the tote bag. The player carries a camera called the instant one-shot camera. The picture quality of the SLR camera is 10. The picture quality of the one-shot is 2. Definition: a camera is sharp if its picture quality is 5 or more. And we will want the photographing action to have the player use the best-quality camera which comes to hand. We will give the action a variable called the 'camera photographed with', thus: The photographing action has an object called the camera photographed with. Every action's variables must be named differently from those of all other actions, because there are some "before" rules (for instance) which take effect for many different actions, and which might need access to any of their variables. So action variables should be named in a way marking out to which action they belong. The best way to do this is to include the past participle of the action name - just as "camera photographed with" contains the past participle "photographed" of the action "photographing". This value is created when the action begins, and disappears when the action ends. (If the action should happen a second time before the first time was completed, a second copy of the value is created, leaving the original undisturbed.) When the action begins, the value starts out as something neutral - so if it is a number, it starts out as 0, if a text, it starts out as the blank text "", and so on. Here it is an object, so it starts out as nothing - the value meaning no object at all. But of course we want to give it a value ourselves. We can do that using the "setting action variables" rulebook. For instance: Setting action variables for photographing: now the camera photographed with is the sharpest camera which is carried by the actor. The "setting action variables" rulebook is run through before even the before rules, and it has no power to stop or change the action. Its rules should say nothing and do nothing other than to set rulebook variables like this one. Note that it is intended to work for any actor, not only the player: so rather than referring to the player as the performer of the action, we need to write "the actor", as in the example above. (See subsequent sections for more on actors.) We can now write rules such as: A check photographing rule: if the camera photographed with is nothing: say "You can hardly photograph without a camera, now can you?" instead. Only rules to do with the photographing action - before, instead, after, check, carry out, or report rules, and so on - are allowed to see the 'camera photographed with' value: it's the private property of the action. A further elaboration allows us to make rules about photographing neater to write. If we create our variable like so: The photographing action has an object called the camera photographed with (matched as "using"). ...then we are now allowed to add an optional 'using ...' clause onto a description of the action. The clause has to be introduced with a single word: here, it's 'using'. For instance, we could write rules such as Instead of photographing something using the one-shot camera: say "But you promised to give this to Sally's nephew." Check photographing something using the noun: say "That would require some sort of contraption with mirrors." instead. Report photographing something using a sharp camera: say "You feel cool and important as the shutter clicks." (This is the method used by the Standard Rules to attach optional clauses such as 'to', 'with' and 'through' to the going action.) Example 198 (*): Removal TAKE expanded to give responses such as "You take the book from the shelf." or "You pick up the toy from the ground." Example 199 (*): Further Reasons Why All Poets Are Liars The young William Wordsworth, pushing a box about in his room, must struggle to achieve a Romantic point of view. Example 200 (*): The Second Oldest Problem Adapting the going action so that something special can happen when going from a dark room to another dark room. Example 201 (**): Puff of Orange Smoke A system in which every character has a body, which is left behind when the person dies; attempts to do something to the body are redirected to the person while the person is alive. Example 202 (***): Croft Adding special reporting and handling for objects dropped when the player is on a supporter, and special entering rules for moving from one supporter to another. 12.11. Making actions work for other people The "photographing" action now works very nicely when the player does it. But not when others try. Suppose that neither the player, nor Clark Gable, is holding the camera: >photograph clark You can hardly photograph without a camera, now can you? >clark, photograph me > An uncanny silence. What has happened is that the rules written so far are all implicitly restricted to the player only. This is because when we write - Check photographing: if the camera is not carried: say "You can hardly photograph without a camera, now can you?" instead. the action is "photographing", not "Clark photographing". In the next few sections we shall see how to make the rules work nicely for everybody. This is a little bit harder, so it should be noted right away that in many projects there is no need. In a game which has no other characters who succumb to persuasion, for instance, only the player will ever try the action. Example 203 (**): The Man of Steel An escaping action which means "go to any room you can reach from here", and is only useful to non-player characters. Example 204 (***): Trying Taking Manhattan Replacing the inventory reporting rule with another which does something slightly different. Example 205 (****): Under Contract Creating a person who accepts most instructions and reacts correctly when a request leads implicitly to inappropriate behavior. 12.12. Check rules for actions by other people If we want to impose the restriction about carrying the camera on other people, we need a rule like the following: Check someone photographing: if the person asked does not carry the camera, stop the action. Implicitly, that "someone" excludes the player. Note that we say nothing in this rule, stopping the action without a word: after all, Clark might well be out of sight when trying this. If he is within sight, then we read: >clark, photograph me Clark Gable is unable to do that. We saw before that Inform's built-in rules all have handy names (the "can't drop what's already dropped rule", and such), and that these are useful when writing better "unable to..." messages. So for a deluxe version, we end up with: Check someone trying photographing (this is the other people can't photograph without the camera rule): if the person asked does not carry the camera, stop the action. And now, with ACTIONS on, we find that: >clark, photograph me [asking Clark Gable to try photographing yourself] [(1) Clark Gable photographing yourself] [(1) Clark Gable photographing yourself - failed the other people can't photograph without the camera rule] Clark Gable is unable to do that. [asking Clark Gable to try photographing yourself - succeeded] which means that we could have, say, Unsuccessful attempt by Clark photographing: if the reason the action failed is the other people can't photograph without the camera rule, say "Clark is too suave to be embarrassed. 'Frankly, my dear, I don't have a camera.'"; otherwise say "Clark tries, and fails, to take a photograph." Example 206 (*): Get Axe Changing the check rules to try automatically leaving a container before attempting to take it. (And arranging things so that other people will do likewise.) Example 207 (***): Barter Barter Allowing characters other than the player to give objects to one another, accounting for the possibility that some items may not be desired by the intended recipients. 12.13. Report rules for actions by other people Report rules for the player's actions are easy to write, and for many actions, they are not much harder for other people either: Report photographing: say "Click!" Report someone photographing: say "Click! [The person asked] takes a snapshot of [the noun]." But once other people are involved, we have to go to some trouble to get all of the possibilities right. Here is a case which did not immediately occur to the author of the "going" action, for instance: >get in cage You get into the cage. >clark, get in automobile Clark Gable gets into the automobile. >clark, push cage west Clark Gable goes west in the automobile, pushing the cage in front, and you along too. The Lot (in the cage) In the Lot you can see an automobile (in which is Clark Gable). We said before that report rules are skipped if the action is running "silently", or if the action is one that the player does not witness. But that is also a tricky concept. Inform's doctrine is that you witness an action if you can see any of the actor, the noun or the second noun at either the beginning or the end of the action; except that being able to see a backdrop does not count. Thus if Clark Gable, in Beverly Hills, photographs the Hollywood sign then we do not witness this from Sunset Boulevard merely because we, too, can see the Hollywood sign. While the report rules for actions by the player must actually report something, report rules for other people's actions are under no such obligation. For instance, if Clark unlocks a door from the other side to the player, then this counts as an action that the player witnesses - and after all, it could be argued that the player should hear the key turning in the lock - but in fact the standard rules for reporting locking choose to say nothing. Example 208 (*): Reporting rules for other characters' behavior Elaborating the report rules to be more interesting than "Clark goes west." Example 209 (***): Fate Steps In Fate entity which attempts to make things happen, by hook or by crook, including taking preliminary actions to set the player up a bit. 12.14. Actions for any actor In the previous sections, we created a new action by providing one set of rules for the player and another for anybody else who might try to perform it. These rules began with action descriptions in one of the following forms: Instead of taking a container, ... Instead of P taking a container, ... The first form implies that the player must be performing the action: the second allows for any person matching P to be the action, except that this person must not be the player. That means that all rules seen so far either affect only the player, or only other people. This is often convenient, but sometimes we need to set up a complicated action which really does work in the same way for every actor - for instance, the built-in Inform actions provided by the Standard Rules aim to do this. We can write such rules thus: Instead of an actor taking a container, ... Here the rule applies to anyone who tries taking a container, player or not. Inside such a rule, the special value 'the actor' is the person performing the action. For instance, the Standard Rules include this one: Carry out an actor wearing (this is the standard wearing rule): now the actor wears the noun. 12.15. Out of world actions The actions seen so far are all impulses causing the protagonist inside the fictional world to do something, or at least try to. But when the player types "quit" or "save", that is not a request for anything to happen in the fictional world: it is an instruction to the program simulating that world. In fact, just the same, such requests are treated as actions, but of a special category called "out of world" actions. They do not cause time to pass by, so the turn counter does not advance, nor does this command cycle count as a turn at all; and they are altogether exempt from "Before", "Instead" and "After" rules. Only the player is allowed to try them. We can also create new out-of-world actions. Suppose we want a dialogue like so: >ROOMS You have been to 1 out of 8 rooms. Here is a complete implementation: Requesting the room tally is an action out of world. Report requesting the room tally: say "You have been to [number of visited rooms] out of [number of rooms] room[s]." Understand "rooms" as requesting the room tally. It is important not to use "out of world" actions for anything affecting what goes on in the fictional world, or realism will collapse, and action-processing may also fail to work in the usual way. "Out of world" actions should be reserved for providing commands like ROOMS, which monitor events rather than participate in them. Example 210 (*): Spellbreaker P. David Lebling's classic "Spellbreaker" (1986) includes a room where the game cannot be saved: here is an Inform implementation. Example 211 (***): A point for never saving the game In some of the late 1970s "cave crawl" adventure games, an elaborate scoring system might still leave the player perplexed as to why an apparently perfect play-through resulted in a score which was still one point short of the supposed maximum. Why only 349 out of 350? The answer varied, but sometimes the last point was earned by never saving the game - in other words by playing it right through with nothing to guard against mistakes (except perhaps UNDO for the last command), and in one long session. 12.16. Reaching inside and reaching outside rules The flow chart back at the start of this chapter shows that, early on in processing an action (between Before and Instead), Inform asks the question "Can we see or touch things?" This is where it enforces the requirements in the action's definition: Photographing is an action applying to one visible thing and requiring light. Scraping it with is an action applying to two things. Seeing and touching are two different questions, which Inform answers in different ways. We shall see ways to modify or entirely alter what can be seen using the "deciding the scope of something" activity when we get to the Understanding and Activities chapters, and later in this chapter we will change the definition of touchability. What both have in common is that they are complicated questions, affected by the circumstances. We cannot simply declare that the player can touch a given lever, or can see in a given room: we must arrange for there to be no barriers between the player and the lever, or for there to be a light source in the room. An example of rules applying to given objects is provided by the way that Inform decides whether the player can reach something or not. For instance, suppose the following: The Laboratory is a room. In the Laboratory is a conical flask. The flask is closed and transparent. In the flask is an antibumping granule. The player will be able to examine the granule but not to take it, as that would require reaching through glass. Suppose the player does type TAKE GRANULE: then Inform looks for potential barriers between the player and the granule, and of course finds the conical flask. If, as in this case, the thing to be touched is on the inside, then Inform asks the "reaching inside" rules for permission. There are two reaching inside rules built in to Inform: can't reach inside rooms rule can't reach inside closed containers rule and in fact the second of these rules will cause the taking action to fail, because the conical flask is a closed container. (The other rule has to do with a player in one room able to see another room through, say, a telescope - merely having a line of sight doesn't give the ability to reach into the frame.) Symmetrically, Inform also has "reaching outside" rules, used if the player is inside something and wants to reach an object in the wider room. (From a bed, probably yes; from a cage, probably no.) This ordinarily contains just one rule: can't reach outside closed containers rule Example 212 (**): Carnivale An alternative to backdrops when we want something to be visible from a distance but only touchable from one room. 12.17. Visible vs touchable vs carried To recap, actions are created like so: Photographing is an action applying to one visible thing and requiring light. Depositing it in is an action applying to two things. Taking inventory is an action applying to nothing. Actions can involve up to two different things. We can place additional requirements on any of these things by describing them as a "visible thing", "touchable thing" or "carried thing". (If we simply say "thing" or "things", as in the second example, Inform assumes the requirement to be "touchable".) These three conditions are increasingly strong: - To be "visible", something needs only to be possible to refer to by the player, which in practice means that it must be visible to the player-character. The noun or second noun produced by any action resulting from a command at the keyboard will always satisfy this minimal condition. - To be "touchable", the player-character must be able to physically touch the thing in question: this normally means that it must be in the same room, and there must be no physical barriers in between. - To be "carried", the player-character must (directly) carry the thing in question. (But if the player types a command using an action requiring something "carried", like WEAR HAT, the thing in question - the hat - will sometimes be picked up automatically. This is called "implicit taking", and results in text like "(first taking the top hat)" being printed.) If an action involves two things, they need not have the same requirement as each other: Waving it at is an action applying to one carried thing and one visible thing. Thus to "wave magic wand at banyan tree", the player must be holding the wand, but need only be able to see the tree. Note one special case. Requirements on touchability are waived in the case of "try" actions applied to people other than the player where the things they would need to touch are doors or backdrops. (This is a compromise to avoid difficulties arising from the ambiguous locations of such items.) Example 213 (**): Eddystone Creating new commands involving the standard compass directions. Example 214 (***): Slogar's Revenge Creating an amulet of tumblers that can be used to lock and unlock things even when it is worn, overriding the usual requirement that keys be carried. 12.18. Changing reachability The question of what the player can, and cannot, reach to touch is important in interactive fiction. It contains some of the subtlest ideas in the model world, though they often go unnoticed. For instance, if a key is on a shelf which is part of a closed box, can we reach for the key? This comes down to whether the shelf, described only as "part of" the box, is on the inside or the outside: and in fact, because it cannot know which is the case, Inform allows either. So in general it is best to regard "parts" as being exterior parts, but to avoid having parts on containers that might in the course of play be closed up with the player inside. We can, if we wish, change the principles of what can be touched by writing new reaching inside or reaching outside rules. Returning to the example of the conical flask: A rule for reaching inside the flask: say "Your hand passes through the glass as if it were not there, chilling you to the bone."; allow access. (Or this could equally be called "a reaching inside rule for the flask".) More generally, we could give the usual flexible description of what the rule applies to: A rule for reaching inside open containers: say "Your hands seem enigmatically too large for [the container in question]."; deny access. The "container in question" is the one to which the rule is being applied. Note that a reaching inside rule can "deny access" (stopping with fail), or "allow access" (stopping with success), or neither, in which case the decision is left up to any subsequent rules in the rulebook to make. If none of them decide, access is allowed. If it seems possible that these rules will be employed by people other than the player, then we need to write them a little more carefully, and in particular we need to ensure that they print nothing for other people. In the first case below, anybody can reach through the glass; in the second case, only the player cannot reach into open containers. A rule for reaching inside the flask: if the person reaching is the player, say "Your hand passes through the glass as if it were not there, chilling you to the bone."; allow access. A rule for reaching inside open containers: if the person reaching is the player: say "Your hands seem enigmatically too large for [the container in question]."; deny access. The "person reaching" is, as its name suggests, the person trying to reach through the barrier in question. Example 215 (*): Magneto's Revenge Kitty Pryde of the X-Men is able to reach through solid objects, so we might implement her with special powers that the player does not have... Example 216 (*): Waterworld A backdrop which the player can examine, but cannot interact with in any other way. Example 217 (**): Dinner is Served A window between two locations. When the window is open, the player can reach through into the other location; when it isn't, access is barred. 12.19. Changing visibility Ordinarily, Inform has a simple model for visibility: it is either fully light or it is fully dark, and certain actions are impossible in the dark, such as examining something. We first need to remember that darkness affects what actions are even tried, as far as the player's typed commands go. If the player is in a dark room, and there is a screwdriver on the floor, the command EXAMINE SCREWDRIVER will not try any action: the screwdriver is not "in scope", which means that the parser thinks the player does not have any means of knowing it exists. (The rules for scope can be modified - see the chapter on Activities.) But let's suppose that the player types EXAMINE BOOK, and is holding the book in question. The book is now "in scope", so the action "examining the book" is tried. Some actions require light to be present, and "examining" is one of those. So Inform consults the visibility rules to see if it can go ahead. By default, there is only one visibility rule, which says "yes" in the light and "no" in darkness. Here, though, we create another one: Visibility rule when in darkness: if examining the book: say "You have to squint. Still..."; there is sufficient light; there is insufficient light. A visibility rule must always conclude "there is sufficient light", or "there is insufficient light", or else do nothing and leave it to other rules to decide. It is a possibly unexpected fact that "looking" does not require light, but instead behaves differently in darkness - it prints a pseudo-room-description such as Darkness It is pitch dark, and you can't see a thing. instead of printing the description of the player's current room. This means that the "looking" action is unaffected by visibility rules. All the same, what "looking" does in the dark can be changed by using the two activities "printing the name of a dark room" and "printing the description of a dark room" (see the Activities chapter for details). Example 218 (*): Flashlight Visibility set so that looking under objects produces no result unless the player has a light source to shine there (regardless of the light level of the room). 12.20. Stored actions As we have seen, to describe an action fully takes a complicated little bundle of information - we need to know what is to be done, who will do it, and what it will be done to. There are times when we would like to remember an action and look back on it later (perhaps many turns later, after many other actions have taken effect) - but this is not easy to do with only the techniques we have seen so far. There are quite a few cases to get right, and it would be easy to not store quite enough of the details. Fortunately, Inform provides a kind of value called "stored action" which can do all of this automatically. As with most other kinds of value, stored actions can be held in variables, "let" values, properties or table columns. For example: The best idea yet is a stored action that varies. creates a variable called "the best idea yet" which holds a stored action. This will normally be created holding the default value - the player waiting. We really only have two ways to make more interesting stored actions:

action of (an action) ... stored action
This phrase produces a literally typed action as a value. Example: now the best idea yet is the action of pushing the button; The action must be specific in every respect, so "action of taking something" or "action of doing something" will not work - "taking something" is really a general description of many possible actions, not an action in its own right.
Note the words "action of...", which convert any sufficiently exact description of an action into its stored action form.

current action ... stored action
This phrase produces the action currently being processed as a value - it literally stores the action, and remembers, if necessary, the exact wording of the player's command at the time it was stored - so that even actions arising from commands like LOOK UP X100 IN THE CODE BOOK can be stored faithfully. Examples: let the present whim be the current action; say "How you would like to be [current action]."; This only makes sense if an action is currently going on, so it shouldn't be used in "every turn" rules, for instance.
So much for making stored actions: now for making use of them. The first obvious idea is to store up an action for several turns and then have it take effect later. That's easily done: just as we can "try" any action written out explicitly, so we can also try a stored one. The phrase to do this has exactly the same wording either way, since it does the same thing either way.

try (stored action)
This phrase makes the stored action take effect now. Example: try the present whim; If the present whim contains, say, the action of taking the beach ball, then the effect is exactly the same as "try taking the beach ball". The stored action isn't destroyed or otherwise used up in the process, so it can be tried again another time, as often as we like.

silently try (stored action)
or: try silently (stored action)
This phrase makes the stored action take effect now, under the "silent" convention which means that routine messages aren't printed. Example: silently try the present whim; If the present whim contains, say, the action of taking the beach ball, and the action succeeds, nothing is printed, but if something goes awry then a message is printed to say why. Either way, the effect is exactly the same as "try silently taking the beach ball".
But stored actions can still be useful even if we never intend to try them. For one thing, we can say them, and this produces a fairly natural description of what the action is: Before doing something in the presence of the bearded psychiatrist: say "'Zo, the subject vishes to engage in [the current action]. Zis is very interesting.'" will produce text such as: "So, the subject vishes to engage in rubbing the fireman's pole. Zis is very interesting." One of Inform's most convenient features is its ability to test if the action being processed matches vague or complicated descriptions of whole classes of actions. Now, it would not make sense to write if the best idea yet is the action of taking something, ... because "action of ..." has to make an exact action, which clearly this is not: so Inform will produce a problem message if we try. But we do not need to, because Inform also allows us to compare a stored action against any description of an action, however vague: if the best idea yet is taking something, ... if the best idea yet is doing something to the lever, ... Just occasionally, this can lead to ambiguities. For instance, if the current action is wearing something, ... fails because Inform thinks "wearing" is meant in the sense of the current action having clothes on, so it produces a problem message. To avoid this, simply write: if the current action is trying wearing something, ... which can't be misunderstood. When dealing with stored actions, we sometimes want to know what they are dealing with. We can extract this information using the following phrases:

action name part of (stored action) ... action name
This phrase produces the action name part of an action. Example: suppose the current actor is Algy, who is throwing the brick at Biggles. Then action name part of the current action = throwing it at

noun part of (stored action) ... object
This phrase produces the (first) noun of an action. Example: suppose the current actor is Algy, who is throwing the brick at Biggles. Then noun part of the current action = the brick If the noun is something other than an object, this produces just "nothing", the non-object.

second noun part of (stored action) ... object
This phrase produces the second noun of an action. Example: suppose the current actor is Algy, who is throwing the brick at Biggles. Then second noun part of the current action = Biggles If the second noun is something other than an object (for instance for the command SET DIAL TO 3417 it would be the number 3417), this produces just "nothing", the non-object.

actor part of (stored action) ... object
This phrase produces the person who would be carrying out the action if it were being tried. Example: suppose the current actor is Algy, who is throwing the brick at Biggles. Then actor part of the current action = Algy
The following phrase is a convenient shorthand form:

if (stored action) involves (object):
This condition is true if the object appears as any of the actor, the noun or the second noun in the action. Example: if the current action involves Algy would be true for "give revolver to Algy", "Algy trying flying the Sopwith Camel", "examine Algy" and so on, but false for "ask Raymond about secret airfield".
Example 219 (*): Bosch Creating a list of actions that will earn the player points, and using this both to change the score and to give FULL SCORE reports. Example 220 (*): Cactus Will Outlive Us All For every character besides the player, there is an action that will cause that character to wither right up and die. Example 221 (**): Actor's Studio A video camera that records actions performed in its presence, and plays them back with time-stamps. Example 222 (**): Anteaters The player carries a gizmo that is able to record actions performed by the player, then force him to repeat them when the gizmo is dropped. This includes storing actions that apply to topics, as in "look up anteater colonies in the guide". 12.21. Guidelines on how to write rules about actions Looking at the action-processing diagram, there seem to be a bewildering number of ways to intervene. For instance, suppose it must be fatal to pick up a land mine. All six of the following rules would do the business: Before taking the land mine: end the story saying "Bang!" Instead of taking the land mine: end the story saying "Bang!" Check taking the land mine: end the story saying "Bang!" Carry out taking the land mine: end the story saying "Bang!" After taking the land mine: end the story saying "Bang!" Report taking the land mine: end the story saying "Bang!" So which should we use? Of course, we could decide that it really doesn't matter: what works, works. But it is a good idea to play along with the conventions used by Inform, if only because that will make our rules interact better with each other and with rules by other people which we may someday want to borrow. So this chapter ends by offering a few guidelines. Let us suppose that we have some effect which we want to achieve. 1. Are we just trying to correct the player's typing? For instance, responding to the command "STEAL GOLDEN EAGLE" with a reply like "To steal something, just try to TAKE it." It is bad style to make a special action for this, which does nothing except to print up this text: better is to use the "Understand ... as a mistake" technique, which will come up in the chapter on Understanding. 2. Does the effect apply only to a particular situation, or is it a general phenomenon? In other words, does the effect apply only to particular people, things or places, or is it a generic rule of play? In the case of the land mine, this is an easy question to answer: it is a unique situation. On the other hand, stopping the player from carrying unduly heavy weights would be a generic rule of play. Rules like the one saying that photography is only possible if one holds the camera are, by convention, also counted as generic rules of play: they are not really special rules about the camera, but apply to all possible acts of photography anywhere, so are actually generic. Sometimes we can choose our own answer to this question, and go either way. Suppose we want a certain place to be muddy-floored, affecting things that happen there. One way would be to write exceptional rules applying to that one room. But we could alternatively create a general concept of muddiness ("A room can be clean or muddy. A room is usually clean.") and then regard the new behaviour as being a set of generic rules applying in muddy rooms. We could then, of course, create a second muddy room with much greater ease, or transplant these rules to other works and have muddy rooms in those too. 3. Particular situations: use Instead or After (or sometimes Before). The next question is: does the effect kick in after the hoped-for action has taken place, or not? In the case of the land mine, to answer that means deciding whether we think the detonator is sensitive to the slightest touch - in which case the explosion would happen at the first touch, and should be in an "Instead" rule - or whether one must actually pick up and disturb the mine - in which case an "After" should be used. That leaves us a choice of two rulebooks if the effect takes place when the merest impulse towards the action is felt: "Before" and "Instead". Which to use? In cases of doubt, choose "Instead". But if the effect is intended to absolutely suppress all such impulses - for instance, in a silent examination room there must be no talking - then "Before" might be more appropriate. We could imagine that someone about to say something first has a mental impulse to speak, then opens his mouth so that it becomes visible to others that some talking is about to go on, and finally utters words. Here are three possible responses: "You cannot contemplate breaking this smothering silence." (Before) "The invigilator stares you down through her horn-rimmed glasses." (Instead) "Everyone turns, appalled, as the silence is broken like the surface of a swimming pool by a falling elephant." (After) 4. Generic situations: work with action rules (or sometimes Before). (a) If the effect takes place only when an action is definitely being tried, then we should use one of the action's three rulebooks: check, carry out or report. Check rules should do nothing, and should say nothing either unless they block the action (in which case, they should say why). Carry out rules must not block the action - it is too late for that - and should not say anything - that hasn't happened yet. (There are a few exceptions: if the action is to look at something, then carrying it out is in a sense the same thing as reporting it. But in all cases of doubt, a carry out rule should say nothing.) Adding a carry out rule to an existing action can make it do something extra. Report rules must neither block the action nor do anything. Working with new report rules is a way to make more natural-seeming, or more informative, messages appear. For instance, an effect where we want to be able to see through a door when it is first opened ("You open the panelled door, through which is the Board Room.") would be a case for a report rule. In all cases, it is good style to write check, carry out or report rules in such a way that they could be used in other works too, or in situations that could conceivably have happened in this one (even if in fact it never does). We may one day want to put our new rules into an extension to be used by other people or in other projects, after all. In this chapter, we have only seen the addition of new rules. We could add a new "check taking" rule, for instance, with the techniques seen so far. But what if the effect we want is not a matter of adding a rule but taking away, or restricting the applicability, of an existing one? In that case, we will need to use "procedural rules" (which will appear in later chapters) to work on the existing ones. The check, carry out and report rules for all of the built-in actions are named, and they appear in the Actions index. (b) If the effect takes place to divert or supplement an action, before that action actually takes place, then this should be done with a "Before" rule. This is the biggest practical use of "Before" rules: to try other actions, either instead or as well as the one just getting under way. For example, if we want an automatic mechanism to try opening a container before taking something inside it, that would be a classic case for "Before". Indeed, that is the only way it could work - "Before" rules have a chance to get in before the touchability conditions are tested. If we wanted a special "stealing" action for the act of taking another person's possessions, we might want to divert any taking action for such items into our new "stealing" action - that too would be a "Before". This would ensure that any "Instead" rules to do with taking do not apply. 5. Changing the behaviour of out-of-world actions. Remember that "Instead", "Before" and "After" do not apply: so use "check" rules to forbid certain out-of-world activities, or procedural rules to abolish the usual "carry out" rule and replace it with a new one. Finally... These are only guidelines. The system is designed to be flexible in order to give the author the widest possible range of options, and nobody should feel ashamed of making use of them. Chapter 13: Relations 13.1. Sentence verbs Descriptions of things - "open door", "people in the Drawing Room" - have already had a whole chapter to themselves. But descriptions are only half of the story of Inform's highly flexible language for talking about places, things and circumstances: this chapter is the other half, and is about the "sentence". Of course all text is made up of sentences, but Inform has a more specific meaning than that. Consider the following pieces of source text: The mouse is in the teapot. Every turn when the mouse is in the teapot, say "A tail hangs out of the spout." Instead of taking the mouse: say "The mouse slips from your hand and disappears into the teapot!"; now the mouse is in the teapot. What these three extracts have in common is the sentence "the mouse is in the teapot". Such a sentence can be used in three different ways: to declare the original state of the world, to ask during play if the world currently has that state, or to change things during play so that it does. Actually, though, only definite sentences about the present can be used in all three ways. A vague instruction like now Mr Darcy can see the mouse; will fail, because there are so many ways in which Darcy might be able to see the mouse that Inform has no way to know how to arrange matters. And this by contrast is not merely difficult but impossible: now Mr Darcy has never seen the mouse; Which cannot be arranged because the past cannot be changed. Verbs also turn up inside the more complicated descriptions. For instance, things which are in the teapot people who can see the mouse are both descriptions, not sentences, but they contain "to be" and "to be able to see" respectively. This chapter is about the verbs which can be used in sentences and descriptions. Inform involves many other features which use verbs - the action "taking the mouse" and the phrase "end the story" both use forms of verbs (to take and to end) - but this chapter has nothing to do with them: so for the sake of clarity, we will call verbs that occur in sentences "sentence verbs". 13.2. What sentences are made up from A sentence consists of two nouns with a verb between them. Usually, the two nouns are descriptions, as in: Mr Collins is in a lighted room. Here "Mr Collins" and "a lighted room" are descriptions, the full rules for which were given in Chapter 5. But there are sentences where one or both of the nouns is a value instead. For instance, in if the score is greater than 10, ... the sentence "the score is greater than 10" consists of two values ("the score" and "10") connected by a verb part ("is greater than"). This chapter is about getting the most out of sentences by defining new verbs to express ideas not already built in to Inform. Before we can define a new sentence verb, however, we must first look at the meanings of verbs: which Inform calls "relations". Example 223 (***): Formal syntax of sentences A more formal description of the sentence grammar used by Inform for both assertions and conditions. 13.3. What are relations? Relations are what sentences express. They are yes/no questions about pairs of things: for example, to say that the coin is in the purse is to say that a particular relation ("being in") is true about a specific pair of things (the coin, the purse). It is neither a fact about the coin nor about the purse, but about the two together. Inform comes with a number of relations built in, almost all of which have been used in previous chapters already. The following table names some of the more useful ones, giving examples of sentences to bring them about: containment relation - The coin is in the purse. support relation - The coin is on the table. incorporation relation - The coin is part of the sculpture. carrying relation - The coin is carried by Peter. wearing relation - The jacket is worn by Peter. possession relation - if Mr Darcy has a rapier... adjacency relation - The Study is east of the Hallway. visibility relation - if Darcy can see Elizabeth... touchability relation - if Darcy can touch Elizabeth... These relation names do not trip off the tongue but do not need to, since relations are referred to only when creating new verbs (as we shall see). The same meaning can often be expressed by using several different verbs, or using the same verb in several different ways, as in the following examples: The coin is in the purse. The purse contains the coin. The coin is contained by the purse. all of which boil down to saying that the coin and purse satisfy the containment relation. Because of that, relations are not the same as verbs. To create a new idea, we will need first to create a new relation, and only then can we set up a verb which allows us to talk about that relation. 13.4. To carry, to wear, to have Inform has altogether five mutually exclusive ways in which one thing can be physically joined to another one: containment relation - The coin is in the purse. support relation - The coin is on the table. incorporation relation - The coin is part of the sculpture. carrying relation - The coin is carried by Peter. wearing relation - The jacket is worn by Peter. This is why we cannot have The coin is on the table. The coin is part of the table. simultaneously, and it is a rare exception to the general rule that having one relation does not affect having another. But there is also a sixth relation used in Inform for these meanings: the possession relation, which is the meaning of the verb "to have". At first sight this looks the same as the carrying relation, but in fact it is a convenient shorthand for "carrying or wearing", provided for conditions rather than assertions: if Mr Darcy has a wet shirt ... will be true during play if he is either carrying or wearing the shirt. Still another relation exists which can be tested, but not declared to be true or false: the concealment relation, which is the meaning of the verb "to conceal". So we can ask: if Mr Darcy conceals a fob watch ... Example 224 (*): Interrogation A wand which, when waved, reveals the concealed items carried by people the player can see. Example 225 (*): Celadon Using the enclosure relation to let the player drop things which he only indirectly carries. 13.5. Making new relations We can create new relations like so: Loving relates various people to one person. Every relation has a name which ends with the word "relation", and in this case the name is "loving relation". While the name is often just two words long, as here, it doesn't have to be: Adept sensitivity relates one person to one vehicle. makes the "adept sensitivity relation". (The limit is 32 words.) In such a definition, we have to say what kind of thing appears on the left and right of any relation, and also whether "one" or "various" possibilities can exist. In the example Loving relates various people to one person. what we are saying is that only people love; that they only love people; and that each person loves only one other person (at any given moment). The "various" part comes in because, for instance, we might have: Verenka loving relation Stankevich Liubov loving relation Stankevich so that various people (Verenka and Liubov, to name but two) love one person (Stankevich). But we are forbidding anyone to love two other people at the same time: Stankevich must decide which of them to love, or pick someone else, or no-one at all. Similarly, we would not allow Liubov loving relation Belinsky It is sometimes convenient to give a name to the other side of a relationship, so to speak. We might imagine: Pet-ownership relates various animals to one person (called the owner). It would then make sense to talk about "the owner of Loulou", and we could have phrases like "now Flaubert is the owner of Loulou" or "if the owner of Loulou is a woman..." and so forth. This, however, would not be allowed: Pet-ownership relates various animals (called the pet) to one person. because "the pet of Flaubert" would be ambiguous: he might have owned dozens. 13.6. Making reciprocal relations The relationships described in this chapter so far are by no means always reciprocated. For instance, if a stone is on a table, then it is never true that the table is also on the stone. And the question may not even be meaningful to ask. If Peter wears a jacket, the jacket does not even have the possibility of wearing Peter. But sometimes we do want a relation which works both ways equally well. These are simple to set up: Meeting relates people to each other. The effect is that various people know various other people, and this is always reciprocated. If Daisy knows Sophie then, automatically, Sophie knows Daisy. This even-handedness is maintained throughout play, so that whatever changes are made it is always true that if A knows B then B knows A. And similarly for a reciprocal relation between one and another: Marriage relates one person to another. In this case, we can again give a name to the partner under a relation: Marriage relates one person to another (called the spouse). and now, for instance, we may have that the spouse of John is Yoko and the spouse of Yoko is John. Since many of these examples have involved people, it might be worth mentioning again that any kind can be involved, not just the "person" kind. Example 226 (***): Four Cheeses A system of telephones on which the player can call distant persons and have conversations. 13.7. Relations in groups Finally, there is a kind of relation which binds even more strongly. Nationality relates people to each other in groups. This is a kind of relation which divides people up: we might wish to have all the Icelandic people related to each other, all the Peruvians to each other, and so on. If there were a Pacific island called Informia with one inhabitant, then that person would be related only to himself. As time goes by, we could imagine people emigrating, and so on, so that these groupings would switch: perhaps everyone would leave Belgium and, for a while, there would be no Belgian nationals at all. (Testing command) The testing command RELATIONS prints out the current state of all the relations created in the source code. For instance: >relations Overlooking relates various rooms to various rooms: The Pub >=> the Garden The Garden >=> the Shrubbery The Shrubbery >=> the Sundial Plot Friendship relates people to each other: Mr Wickham Sophie Charlotte Sophie Marriage relates one person to another: Mr Wickham == Sophie That can produce a lot of output. To see only a single relation, or to see it at some intermediate point in a calculation, there's also a testing phrase:

show relation (relation of values to values)
This phrase is for testing purposes only. It shows the current state of the named relation, that is, it shows which values relate to which other ones, where it's possible to do this in any sensible way.
But this is a phrase - not a typed command. Example 227 (*): Transmutations A machine that turns objects into other, similar objects. Example 228 (***): Otranto A kind of rope which can be tied to objects and used to anchor the player or drag items from room to room. 13.8. The built-in verbs and their meanings It is all very well to define new relations, but this does nothing if there is no way to assert that they are true, or to ask whether they are true or false. That requires a verb: in fact, a relation is nothing more than what Inform uses as the "meaning" of a verb. The assertion verbs built in to Inform have the following built-in relations as their meanings: Verb - Relation to be - equality relation to have - possession relation to contain - containment relation to support - support relation to carry - carrying relation to wear - wearing relation to incorporate - incorporation relation Two of Inform's built-in relations are expressed using prepositions instead: Preposition - Relation to be part of - (reversed) incorporation relation to be adjacent to - adjacency relation It would be easy to make verbs for these if we wanted ("to adjoin", say) using the techniques of the next section. The verb to be is grammatically different from any other, and its meaning is too complicated to be fully expressed by any one relation. A great deal of the Inform program is given over to its "meaning", which we are not allowed to change or imitate. The "equality relation" is simple enough, and is the one implied by conditions like if the score is 20, ... but to be can have more complicated implications - "if Mr Wickham is hungry" clearly doesn't test whether two quantities are equal. Fortunately the other verbs are much simpler. 13.9. Defining new assertion verbs Here is an example definition of a new verb: The verb to sport (he sports, they sport, he sported, it is sported, he is sporting) implies the wearing relation. Once this is done, we can write the assertion Mr Wickham sports a Tory rosette. which will do the the same thing as Mr Wickham wears a Tory rosette. because both verbs have the same relation as their meaning. Note that we have to spell out many parts of the verb: to sport - infinitive he sports - present singular they sport - present plural he sported - past it is sported - past participle he is sporting - present participle Although it looks as if Inform could easily generate these given the infinitive "to sport" alone, by adding an "-s" here or an "-ed" there, English can be a very irregular language. Since only a few verbs will be defined in any single project it seems best to be explicit. (If we do miss out any of the parts of the verb, the result will be that the usages missed out will not be understood by Inform. Sometimes that's a good thing, as some verbs have seldom-used present participles, for instance - "he is liking me", for instance, is grammatical but odd.) Occasionally it's convenient to have the relation the other way around. For instance: The verb to grace (he graces, they grace, he graced, it is graced, it is gracing) implies the reversed wearing relation. With that defined, these two sentences have identical meanings: Mr Wickham sports a Tory rosette. A Tory rosette graces Mr Wickham. Reversed in this sense means that the things related - the subject and object of the verb - are the other way round. The Phrasebook index contains all the verbs associated with assertions, in the "table of verbs" section. When we add new verbs to our source, those will appear in the Phrasebook as well. The verbs above ("to grace", "to sport") are short ones, but we're free to make them longer than that. For example: The verb to cover oneself with (he covers himself with, they cover themselves with, he covered himself with, he is covering himself with) implies the wearing relation. Peter is covering himself with a tent-like raincoat. Here we have "to cover oneself with", four words long; the limit is 29. Example 229 (*): Unthinkable Alliances People are to be grouped into alliances. To kiss someone is to join his or her faction, which may make a grand alliance; to strike them is to give notice of quitting, and to become a lone wolf. Example 230 (***): The Unexamined Life An adaptive hint system that tracks what the player needs to have seen or to possess in order to solve a given puzzle, and doles out suggestions accordingly. Handles changes in the game state with remarkable flexibility, and allows the player to decide how explicit a nudge he wants at any given moment. 13.10. Defining new prepositions The term preposition is used here, a little loosely, to mean anything which we add to the verb to be in order to talk about some relation or other. We have seen many examples already, such as: To be in - The ball is in the box. To be part of - The lever is part of the slot machine. These are easier to create than verbs, because Inform already knows the wayward grammar of to be, so we need not give any of the principal parts. Otherwise, the method is exactly the same. Compare the definitions in the following: Suspecting relates various people to one person. The verb to suspect (he suspects, they suspect, he suspected, it is suspected, he is suspecting) implies the suspecting relation. The verb to be suspicious of implies the suspecting relation. The result of this is that Hercule Poirot suspects Colonel Hotchkiss. Hercule Poirot is suspicious of Colonel Hotchkiss. are exactly equivalent, and so are these two descriptions: somebody who suspects Colonel Hotchkiss somebody suspicious of Colonel Hotchkiss While most prepositions are short ("in", "part of", "suspicious of"), they're free to be longer if need be ("very far away from"): the limit is 30 words, which should be ample. We can also define verbs as auxiliaries, like so: The verb to be able to approach (he is approached) implies the approachability relation. Now we can ask if Poirot "can approach" Hotchkiss, and so on. (Here again we need not spell out the other parts of the verb.) Example 231 (*): The Abolition of Love A thorough exploration of all the kinds of relations established so far, with the syntax to set and unset them. Example 232 (*): Swerve left? Swerve right? Or think about it and die? Building a marble chute track in which a dropped marble will automatically roll downhill. Example 233 (*): Beneath the Surface An "underlying" relation which adds to the world model the idea of objects hidden under other objects. Example 234 (***): Bogart Clothing for the player that layers, so that items cannot be taken off in the wrong order, and the player's inventory lists only the clothing that is currently visible. 13.11. Indirect relations We have already seen, in the chapter on Descriptions which is a forerunner of this one, that Inform provides not only "adjacent" as a way of seeing if one room is directly connected to another, but also "the best route from A to B", which allows us to see if any sequence of moves connects them. Something similar - in fact, simpler - is allowed for any relation between objects. Suppose we would like to go sledging: we can go downhill, but not up. Some quite distant places may be reachable, while others close by may not be, even if lower than us, because they would involve climbing again at some point. The following would implement this: Overlooking relates various rooms to various rooms. The verb to overlook (it overlooks, they overlook, it overlooked, it is overlooked, it is overlooking) implies the overlooking relation. The Garden overlooks the Shrubbery. The Folly overlooks the Garden. The Shrubbery overlooks the Sundial Plot. The Old Ice House overlooks the Garden. After looking: say "This wintry vantage point overlooks [the list of rooms overlooked by the location]."; let the way be the next step via the overlooking relation from the location to the Sundial Plot; if the way is a room, say "To sledge downhill to the Sundial, aim for [the way]."; otherwise say "It is not possible to sledge downhill to the Sundial." Here we're making use of:

next step via (relation of values to values) from (object) to (object) ... object
This phrase tries to find a shortest route between the two given endpoints, using the given relation of objects to determine single steps. Example: next step via the overlooking relation from the Folly to the Chinese Lake The result is the special object value "nothing" if the two endpoints are the same or if no route exists.

number of steps via (relation of values to values) from (object) to (object) ... number
This phrase tries to find the length of a shortest route between the two given endpoints, using the given relation of objects to determine single steps. Example: number of steps via the overlooking relation from the Folly to the Chinese Lake The result is 0 if the two endpoints are the same, or -1 if no route exists.
Another example would be the "six degrees of separation" game, where it is claimed that any two people on Earth are connected by a sequence of up to six acquaintances. In an Inform implementation, we might talk about "the next step via the friendship relation from George Bush to Saddam Hussein", for instance, a phrase likely to evaluate to Donald Rumsfeld, and then the number of steps via the friendship relation from George Bush to Saddam Hussein would be... but that would be telling. As with route-finding through the map, finding "the next step via" a relation can be slow. For instance, suppose we have dozens of articles of clothing all partially revealing each other, connected by two relations - overlying and underlying. Then "the next step via" these relations allows us to establish what can be worn on top of what else. If we need to calculate this often, and there are enormous wardrobes of clothes to choose from, speed starts to matter. Once again there is a choice of algorithms: "fast" and "slow", where "fast" needs much more memory. To make route-finding for a given relation "fast", we have to declare it that way: Overlying relates various garments to various garments with fast route-finding. Overlapping relates various garments to each other with fast route-finding. Otherwise, the "slow" method will be used. This "with fast route-finding" note can only be added to various-to-various relations. (Although route-finding through various-to-one and one-to-various relations is fully supported, it exploits the relative simplicity of these problems to use a more efficient algorithm than either "fast" or "slow".) (- See Adjacent rooms and routes through the map for route-finding through the map rather than a relation.) Example 235 (***): The Problem of Edith A conversation in which the main character tries to build logical connections between what the player is saying now and what went immediately before. 13.12. Relations which express conditions One last way to create a new relation and, in many ways, the easiest of all. If we write: Contact relates a thing (called X) to a thing (called Y) when X is part of Y or Y is part of X. The verb to be joined to implies the contact relation. then we would be able to talk about a handle being joined to a door, and a door being joined to a handle, and so on. We are not allowed to declare: The hook is joined to the line. because the question of whether they are joined is not for us to decide: that will be for the condition to determine, whenever we test it. Similarly, we cannot meaningfully write now the hook is joined to the line; (and Inform will not let us) because this relation is not something we can force either way: we can make it come true by other means, maybe, but we cannot simply make it true by saying so. Lastly, this kind of relation is restricted in that we are not allowed to find paths or calculate numbers of steps through it. So this way to define relations is, on the face of it, just a sort of verbal trick to write conditions in a more attractive way. The more flexible, changeable relations in previous sections have much greater expressive power. All the same, it is nice to be able to write - Nearness relates a room (called A) to a room (called B) when the number of moves from B to A is less than 3. The verb to be near implies the nearness relation. and then to be able to write rules like: Instead of listening when the location is near the Sundial: say "You hear a splashing of water." As with other relations, there's no reason why we have to use objects. For example: Material is a kind of value. The materials are wood and metal. A thing has a material. Materiality relates a thing (called X) to a material (called Y) when Y is the material of X. The verb to be made of implies the materiality relation. which enables us to write: if the cube is made of wood, ... say "The carpenter looks at [the list of things which are made of wood]."; And here is a mathematical one: Divisibility relates a number (called N) to a number (called M) when the remainder after dividing M by N is 0. The verb to divide (it divides, they divide, it divided, it is divisible) implies the divisibility relation. The verb to be a factor of implies the divisibility relation. We now find that "2 divides 12", "5 is not a factor of 12" and "12 is divisible by 3" are all true. Again, we are only really gaining a nice form of words, but improving the clarity of the source text is never a bad thing. Example 236 (*): Wainwright Acts A technical note about checking the location of door objects when characters other than the player are interacting with them. Example 237 (***): A Humble Wayside Flower Relations track the relationships between one character and another. Whenever the player meets a relative of someone he already knows, he receives a brief introduction. 13.13. Relations involving values Although most of the examples in this chapter have involved objects, relations can connect almost any values together. We can create relations in groups, one to various relations, various to one relations, one to one relations, and various to various relations for any combination of kinds. For example: Partnership relates various texts to various texts. The verb to belong with (he belongs with, they belong with) implies the partnership relation. "cheese" belongs with "crackers". "clam" belongs with "chowder". How might we make use of this? Clearly it would be impractical to keep trying: if "caviar" belongs with "aardvarks", ... if "caviar" belongs with "abacuses", ... ... to find out what "caviar" belongs with. It's still harder to find out if it belongs with anything at all -- in theory we would have to try every possibility, which of course is impossible. Instead we have these phrases:

if (value) relates to (name of kind) by (relation of values to values):
This condition is true if the value V is such that V relates to something by the given relation. Example: suppose partnership relates various texts to various texts. Then we can test if "chalk" relates to a text by the partnership relation, ...

if (name of kind) relates to (value) by (relation of values to values):
This condition is true if the value V is such that something relates to V by the given relation. Example: suppose partnership relates various texts to various texts. Then we can test if a text relates to "cheese" by the partnership relation, ...
If a partner does exist, then we can find it with:

(name of kind) to which/whom (value) relates by (relation of values to values) ... value
or: (name of kind) that/which/whom (value) relates to by (relation of values to values) ... value
This phrase produces an Y such that the given value V relates to Y by the given relation. Example: suppose partnership relates various texts to various texts. Then we can obtain the text to which "chalk" relates by the partnership relation which might be, say, "cheese". It's a run-time problem to use this if no such Y exists.

(name of kind) that/which/who relates to (value) by (relation of values to values) ... value
This phrase produces an X such that X relates to the given value V by the given relation. Example: suppose partnership relates various texts to various texts. Then we can obtain the text which relates to "cheese" by the partnership relation which might be, say, "chalk". It's a run-time problem to use this if no such X exists.
Of course, there might be many answers to this question, so perhaps these are neater:

list of (name of kind) that/which/who relate to (value) by (relation of values to values) ... value
This phrase produces a list of all the X such that X relates to the given value V by the given relation. Example: suppose partnership relates various texts to various texts. Then we can obtain list of texts which relate to "cheese" relates by the partnership relation which might be, say, { "chalk", "grapes", "macaroni" }. The answer might be the empty set, but that's not a problem.

list of (name of kind) to which/whom (value) relates by (relation of values to values) ... value
or: list of (name of kind) that/which/whom (value) relates to by (relation of values to values) ... value
This phrase produces a list of all Y such that the given value V relates to Y by the given relation. Example: suppose partnership relates various texts to various texts. Then we can obtain list of texts to which "chalk" relates by the partnership relation which might be, say, { "cheese", "blackboard", "cliffs" }. The answer might be the empty set, but that's not a problem.
Finally, it's sometimes useful to get at the list of all values which can appear on the left or right hand side of a relation. We need tongue-twister like wording to do it, but:

list of (name of kind) that/which/whom (relation of values to values) relates ... value
This phrase produces a list of all X which relate to anything under the given relation. Example: suppose partnership relates various texts to various texts. Then we can obtain list of texts which the partnership relation relates

list of (name of kind) to which/whom (relation of values to values) relates ... value
or: list of (name of kind) that/which/whom (relation of values to values) relates to ... value
This phrase produces a list of all Y which anything relates to under the given relation. Example: suppose partnership relates various texts to various texts. Then we can obtain list of texts which the partnership relation relates to
For efficiency reasons, there are no guarantees about what order these lists have - but they can of course always be sorted when found. Example 238 (*): Meet Market A case in which relations give characters multiple values of the same kind. Example 239 (***): For Demonstration Purposes A character who learns new actions by watching the player performing them. 13.14. Relations as values in their own right As we've seen, most relations have names - "containment relation", for instance. These are themselves values in Inform, though there are a few restrictions on how they are used. (Relations can contain a colossal amount of data, so we don't want to have to copy them casually.) Consider these two examples: Parity relates a number (called N) to a number (called M) when N minus M is even. Joint magnitude relates a number (called N) to a number (called M) when N plus M is greater than 7. Here "parity relation" and "joint magnitude relation" are both values of the same kind: "relation of numbers to numbers". In general, every relation is a value of kind "relation of K to L", for the appropriate kinds K and L. So the parity relation doesn't have the same kind as the containment relation, for example. Because it often happens that K and L are the same, we can just say "relation of K" in this case, so we could equally say that the kind of the parity relation is "relation of numbers". This is useful to know when writing phrases like so: To chart (R - a relation of numbers): repeat with N running from 1 to 5: repeat with M running from 1 to 5: if R relates N to M, say "[N] [M] "; say "[line break]"; and now "chart parity relation" will work nicely, but "chart visibility relation" will be rejected (as it should be, because it relates things, not numbers). In general, if R is any relation, we can write if R relates X to Y, ... now R relates X to Y; now R does not relate X to Y; to test, set and unset a relation R between two values. (Inform checks that the values X and Y have the right kind and produces a problem message if not.) Several useful adjectives can be applied to relations: "empty" - nothing relates to anything else "symmetric" - by definition X relates to Y if and only if Y relates to X "equivalence" - this is a relation "in groups", or an "equivalence relation" "one-to-one" - it relates one K to one L "one-to-various" - similarly "various-to-one" - similarly "various-to-various" - similarly So for example it's possible to ask if R is a symmetric one-to-one relation of texts, ... With some relations, it's possible to clear them out by writing: now R is empty; and with temporary relations (see the next section), it's even possible to change their valencies (one-to-one vs. one-to-various, etc.) using "now", but only when they are empty. The exceptions where "empty" can't be used are those which can't be changed at all, like the parity relation above, and a few built-in cases such as the support, containment and incorporation relations, where emptying would dissolve the model world in a disastrous way. Example 240 (*): Number Study The parity and joint magnitude relations explored. 13.15. Temporary relations So far in this chapter, we've only seen relations which exist permanently during play. The relationships might change - sometimes Red Riding Hood would be in the Woodcutter's Cottage, sometimes not - but the relations themselves were eternal. In fact, though, we can also create relations to be dynamic data structures, like lists or indexed texts:

let (a name not so far used) be (description of relations of values to values)
This phrase creates a new temporary variable, and sets its value to the identity of a newly created and equally temporary relation. These last only for the present block of phrases, which certainly means that they exist only in the current rule. Example: let the password dictionary be a relation of texts; This makes a purely temporary various-to-various relation between texts, which lasts as long as the temporary value "password dictionary" lasts. By default, relations are various-to-various, but we could instead write, say: let the nicknames catalogue be a various-to-one relation of texts;
Such a relation exists only in the current phrase, and is destroyed when the phrase finishes, like any other "let". Of course there's no verb whose meaning is this relation, but that's no obstacle, because we can manipulate it using "relates": now the nicknames catalogue relates "Trudy" to "Snake-eyes"; (At present such a relation cannot be used outside its own phrase.) 13.16. What are relations for? It is easy to say what verbs are for: they are to express relations. But what are relations for? Inform 7's focus on relations between objects is unusual as an approach to interactive fiction; the concept does not exist in most design systems, or rather, it does but is submerged. Traditional design systems do, after all, have the spatial relations of being inside, on top of, and so on. It could well be said that these are the only relationships that inanimate objects ever have. A stone can be on top of a table, and if so then that expresses their entire association. This is because the stone, and the table, have no opinions, emotions, knowledge or memory. If the stone is taken away and then put back, nothing has changed. People, on the other hand, tend to remember having met each other before; they like being in some places, but not others; their behaviour depends on who, or what, is nearby. Being conscious, they have internal states, unlike the stone. Relations are a simple but powerful way to express and talk about such connections, and although they have numerous uses in physical contexts too, they are at their most powerful when helping to make the characters of interactive fiction come alive. Example 241 (**): Murder on the Orient Express A number of sleuths (the player among them) find themselves aboard the Orient Express, where a murder has taken place, and one of them is apparently the culprit. Naturally they do not agree on whom, but there is physical evidence which may change their minds... Example 242 (**): What Not To Wear A general-purpose clothing system that handles a variety of different clothing items layered in different combinations over different areas of the body. Example 243 (***): Mathematical view of relations Some notes on relations from a mathematical point of view, provided only to clarify some technicalities for those who are interested. Example 244 (***): Graph-theory view of relations Some notes on relations from the point of view of graph theory. 13.17. Review of Chapter 13: Relations 1. Existing relations. As we have seen, the following relations are defined by default in Inform: Verb - Relation to contain - containment relation to support - support relation to carry - carrying relation to wear - wearing relation to unlock - unlocking relation The meanings of these are explained in the chapter on Things. Two of Inform's built-in relations are expressed using prepositions instead: Preposition - Relation to be part of - incorporation relation to be adjacent to - adjacency relation The meaning of parts is discussed in the chapter on Things. Adjacency is explained in the chapter on Descriptions. Finally, there are conditional relations defined by Inform in advance: Verb/Preposition - Relation to be able to see - visibility relation to be able to touch - touchability relation to have - a superset of the carrying and wearing relations (possession relation) to enclose - indirect containment/support/incorporation relation to hold - direct containment/support/incorporation relation The meaning of visibility and touchability is discussed further in the chapter on Descriptions (and further under Advanced Actions); enclosure in the chapter on Things. We may review the relations that are currently defined by Inform or by our own code by looking at the bottom of the Phrasebook in the Index. 2. Creating new relations. We have already used the example: Loving relates various people to one person. Let us create a verb which expresses this: The verb to love (he loves, they love, he loved, he is loved) implies the loving relation. Note that we have omitted one of the parts of the verb. Actually we can legally miss out any of them, but the result is that the usages missed out will not be understood by Inform. In this case, Inform will understand Elizabeth loves Darcy. if anybody has been loved by Darcy, ... someone who is loved by Elizabeth the number of women who love Darcy but it will not understand Elizabeth is loving Darcy. if Darcy is loving anybody, ... because we did not supply the present participle "he is loving" as part of the definition of the verb. (That was deliberate, because the verb "to love" isn't used that way.) Similarly, using our reciprocated relation for mere acquaintanceship, Meeting relates people to each other. The verb to know (he knows, they know, he knew, he is known) implies the meeting relation. Elizabeth knows Mr Wickham. Mr Wickham knows Mr Darcy. We may also create two special formats of relation verb: The verb to be angry at implies the fury relation. The verb to be able to beat (he is beaten) implies the superiority relation. In the first case, we will then be able to test (and set) the relation with standard forms of the verb to be, as in if anyone is angry at Marie Antoinette, ... now the Professor is angry at Gilligan. and in the second, we may use such forms as if Fred can beat George, ... if Fred is able to beat your George, ... now Mistress Eva is able to beat the player. now the player can be beaten by Mistress Eva. and so on. 3. Relation types. A relation can be characterized by three aspects: the number of entities allowed to participate in each side of the relation, whether the relation is reciprocal, and whether relation to one member of the group indicates the same relation to all the other members. This does not produce quite as many combinations as one might at first expect. We cannot, of course, have a reciprocal relation that is unbalanced -- there is no such thing as a reciprocal one-various or various-one relation. Similarly, relations in groups must be various-various. Thus we may say Nationality relates people to each other in groups. (grouping, effectively reciprocal, various-various) Marriage relates one person to another. (reciprocal, one-one) Meeting relates people to each other. (reciprocal, various-various) Orbit relates one gravitational body to one gravitational body. (not reciprocal, one-one) Patronage relates one person to various people. (not reciprocal, one-various) Underlying relates various things to one thing. (not reciprocal, various-one) Admiration relates various people to various people. (not reciprocal, various-various) In addition to these, we may write conditional relations, such as Contact relates a thing (called X) to a thing (called Y) when X is part of Y or Y is part of X. The verb to be joined to implies the contact relation. These are considerably more restricted than other types of relation, and exist chiefly to allow more expression in our source text. We cannot set conditional relations by fiat (as in "now the hook is joined to the line"). Furthermore, it is not possible to find a best route through a conditional relation. Conditional relations can be used to express the relation between things and values, as well, so that we can make more elegant phrasings for the properties of things. 4. Setting and unsetting relations. As usual, "now" can be used to change the state of the relation: now Elizabeth loves Bingham But Inform will not allow this: now Elizabeth does not love Bingham because, given the various-to-one nature of the relation, Inform knows that Elizabeth must love either one specific person or else nobody. It therefore thinks that ruling out specific individuals, as here, is misleading. Instead, we can cast Elizabeth adrift with an open heart thus - now Elizabeth does not love anybody Such instructions are required to use the right kind: here we have "anybody" since the object of Elizabeth's love must be a person. For a relation of various people to one room, it would be "anywhere"; for a relation of various people to one thing, it would be "anything". 5. Finding indirect relations. Relations other than conditional relations may be used to find shortest paths between things: so that we may talk about the next step via the overlooking relation from the location to the Sundial Plot the number of steps via the overlooking relation from the location to the Sundial Plot The number of steps -- as with pathfinding through rooms, a special case -- will be 0 if the location is the Sundial Plot, and -1 if there is no possible route between the two by this relation. Chapter 14: Numbers and Equations 14.1. How do we measure things? In a poem, or in a novel, exact scientific measurements are not the point. So a writer who wants to set up ways to describe the sky at different times might go for something like this: The sky can be cadmium, mackerel, overcast or cornflower. And nobody is interested in the sun angle, the percentage of cloud cover, or any of the other numbers behind all of this. Similarly, if we walk into a familiar office which has been disturbed, we might well say "Look! The filing cabinet is in the middle of the floor." We are not likely to exclaim "Look! The filing cabinet is 1.2m from the east wall and 2.1m from the north wall." But some writers of interactive fiction do like to make use of physical realism. For instance, it's easier to forbid a bulky object being taken through a narrow doorway if there is a way to measure and compare sizes. Most computer programs write numbers in the same way, whatever they're used for. But human beings don't. If someone says "How far is Duluth?", we're more likely to say "100 miles" than just "100". This is a useful feature of natural language, because it means we always know how to translate that number into reality - it's 100 miles, not 100 km, or 100 inches; and it's definitely a distance, not 100 apples or 100 kilograms. Inform lets us use plain numbers if we want to, but it also allows us to create numerical kinds of value: A distance is a kind of value. 5 miles specifies a distance. That kind of definition, and the consequences, will be the subject of this chapter. But we will first look a little harder at the numerical kind of value we get for free: "number". 14.2. Numbers What Inform calls a "number" is a whole number, positive, negative or zero. The range of numbers we can hold is not unlimited - if the format Setting for a project is one of the Z-machine choices, then we have: -32768, -32767, ..., -3, -2, -1, 0, 1, 2, 3, ..., 32767 and if it is set to Glulx, then we have: -2147483648, -2147483647, ..., -3, -2, -1, 0, 1, 2, 3, ..., 2147483647 Numbers from zero to twelve may be written out, but larger ones must be written as numerals. So "twelve" or "12", but "13" only. We are allowed to perform about the same operations on numbers as are provided by a simple office calculator, starting with addition, subtraction, multiplication and division. We can use the traditional typewriter symbols for these, +, -, * and /, or can spell them out in words as "plus", "minus", "times" (or "multiplied by"), and "divided by". Definitively:

(arithmetic value) + (arithmetic value) ... value
or: (arithmetic value) plus (arithmetic value) ... value
This phrase performs signed addition on the given values, whose kinds must agree, and produces the result. Examples: 200 + 1 = 201 10:04 AM + two minutes = 10:06 AM

(arithmetic value) - (arithmetic value) ... value
or: (arithmetic value) minus (arithmetic value) ... value
This phrase performs signed subtraction on the given values, whose kinds must agree, and produces the result. Examples: 200 - 1 = 199 10:04 AM - two minutes = 10:02 AM

(arithmetic value) * (arithmetic value) ... value
or: (arithmetic value) times (arithmetic value) ... value
or: (arithmetic value) multiplied by (arithmetic value) ... value
This phrase performs signed multiplication on the given values, whose kinds must be dimensionally compatible, and produces the result. Examples: 201 times 3 = 603 two minutes times 4 = eight minutes

(arithmetic value) / (arithmetic value) ... value
or: (arithmetic value) divided by (arithmetic value) ... value
This phrase performs signed division on the given values, whose kinds must be dimensionally compatible, and produces the result. Examples: 201 divided by 3 = 67 twenty minutes divided by 4 = five minutes twenty minutes divided by five minutes = 4 Division rounds down to the nearest whole number. It is mathematically impossible to divide by 0, so any attempt to do so will cause a run-time problem message.

remainder after dividing (arithmetic value) by (arithmetic value) ... value
This phrase performs signed division on the given values, whose kinds must be dimensionally compatible, and then produces the remainder. Examples: remainder after dividing 201 by 5 = 1 remainder after dividing twenty minutes by 7 = six minutes It is mathematically impossible to divide by 0, so any attempt to find the remainder after dividing by 0 will cause a run-time problem message.
The verbal and symbolic forms of these phrases are equivalent: the score + 10 the score plus 10 It's probably better style to spell them out in full when writing text, and keep the symbols for writing equations, as we'll see later on in the chapter. (If we do use the symbols, then spaces around them are obligatory: to Inform, they are words which just happen to be spelt with symbols instead of letters.) Arithmetic often produces fussily exact answers which seem inappropriate in a conversation. Nobody says "Steeple Barton is 7.655 miles down the road", but "Steeple Barton is eight miles down the road" sounds perfectly normal. In order to make that sort of report easier to make, Inform provides another arithmetic operation, one that's not found in most computer programming languages:

(arithmetic value) to the nearest (arithmetic value) ... value
This phrase rounds the given value off, rounding upward in boundary cases. Examples: 201 to the nearest 5 = 200 205 to the nearest 10 = 210 10:27 AM to the nearest five minutes = 10:25 AM
Inform has very few mathematical functions built in as phrases, because these aren't very often needed in story-telling. But it does provide these:

square root of (arithmetic value) ... value
This phrase produces an approximate square root, to the nearest integer, of the given value, which must be of a kind which has square roots. Example: square root of 16 = 4 Trying to take the square root of a negative number will cause a run-time problem, because then we can't even nearly solve it.

cube root of (arithmetic value) ... value
This phrase produces an approximate cube root, to the nearest integer, of the given value, which must be of a kind which has cube roots. Example: cube root of 27 = 3 cube root of -27 = -3
We can compare numbers using either the traditional computer-programming symbols, or using words: if the score is less than 10 if the score < 10 and similarly for "greater than", "at least" and "at most", with the symbols ">", ">=" and "<=". But we are not allowed the equals sign: for that we need only use "is" - if the score is 10 14.3. Units Suppose we want to talk about how tall people are. We could just create a "number" property, like this: A person has a number called height. But then we would have to write lines like "Isabella has height 68", which nobody would naturally say. What we want is to be able to write "Isabella is 5 foot 8." Perhaps the computer will need to store that measurement as the number 68 in some register or other, but we don't want to know about that. "5 foot 8" is a complicated notation in a way - it involves both feet and inches - so let's start with a simpler example: A weight is a kind of value. 10kg specifies a weight. This is a little different to the kinds of value seen so far, which were all created like so: A colour is a kind of value. The colours are red, green and blue. We can't mix the two styles: a new kind of value will either be numerical at heart ("10kg") or verbal at heart ("blue"). The effect of "10kg specifies a weight" is to tell Inform that this is the notation for writing a constant "weight". So, for instance, The maximum load is a weight that varies. The maximum load is 8000kg. if the maximum load is greater than 8000kg, ... Inform is then careful not to allow weights to be mixed up with other numerical values. For instance, it won't allow "if the maximum load is 400", because 400 is a number, not a weight. More or less anything we can do with numbers, we can now do with weights. For instance, we can write: The Weighbridge is a room. "A sign declares that the maximum load is [maximum load]." ...which will produce the text "A sign declares that the maximum load is 8000kg." Numerical kinds of value are sometimes called "units", because one of their main uses is to allow us to write quantities using scientific units such as kilograms. But they have other uses too. We have a great deal of freedom in creating notations like "10kg", or "4 foot 10" - the main thing is that new notations must not already mean a value. So "10 specifies a weight" will not be allowed, because 10 specifies a number already. Sometimes it is unnatural to write negative values, and so Inform will issue a Problem message if this is tried - for instance, Inform would not allow us to write a weight of -4 kg. (This doesn't mean that arithmetic on units is forbidden to get a negative result: we may want to work out the difference between two weights. Inform's Problem message is simply to try to prevent the accidental writing of incorrect values.) If we do want the ability to write negative values in the source text, we signal that in the notation itself: -10 kg specifies a weight. That alerts Inform that both positive and negative values for this unit make sense. If we set up a spread of multiple notations (see the next section) then this is automatically enabled, because then we're clearly dealing with proper physics, where negative values are common. Example 245 (*): rBGH The player character's height is selected randomly at the start of play. Example 246 (**): Wonderland Hiking Mount Rainier, with attention to which locations are higher and which lower than the present location. 14.4. Multiple notations Going back to our weight example: A weight is a kind of value. 10kg specifies a weight. The notation here is a single word, even if it contains digits as well as letters - "10kg". But it doesn't have to be one word. These would have worked, too: 10kg net specifies a weight. 10 kg specifies a weight. In fact, we are allowed to have all three at once, as alternatives: A weight is a kind of value. 10kg specifies a weight. 10kg net specifies a weight. 10 kg specifies a weight. If we often have to deal with large weights, it becomes a little cumbersome to keep on writing something like "80000kg". An engineer would write "80 tonnes" for this. Similarly, we wouldn't like road maps to use light years, or speed limit signs to use furlongs per fortnight. So it's sometimes useful to provide a spread of different notations, at different scale factors, for the same kind of value. Here's one way of setting up the tonne, that is, the metric ton: 1 tonne specifies a weight scaled up by 1000. This really is an alternative way to write the same thing: for instance, Inform will allow "25kg plus 3 tonne", the result being "3.025 tonne". That's all very well, but a value like "3 tonne" reads a little oddly, even if it's correct in theory. Outside of scientific journals with old-school copy editing, most people would write "3 tonnes", not "3 tonne". Here's a better try: 1 tonne (singular) specifies a weight scaled up by 1000. 2 tonnes (plural) specifies a weight scaled up by 1000. Now Inform will not only recognise both forms, but also use the right one when printing back. 14.5. Scaling and equivalents As we've seen, we can provide differently scaled notations for the same unit: A length is a kind of value. 1m specifies a length. 1km specifies a length scaled up by 1000. And this allows us to write "0.45km" instead of "450m", if we want to, both having the same effect. Just as we can scale up, so we can also scale down: 1cm specifies a length scaled down by 100. Now we have a spread of three notations, so "3cm", "0.03m" and "0.00003km" all mean the same thing. But something quite interesting happened at the same time: Inform realised that we want to know lengths to a greater accuracy than just a whole number of meters. We sometimes have to remember that all of these values are stored exactly as integers. If we want to resolve down to very small values, that reduces the size of the largest value we can have. For instance, with the Glulx format setting, writing just A length is a kind of value. 1m specifies a length. gives us a range of 1m up to 2147483647m, which is plenty - it's about six times the distance from the Earth to the Moon. Going down to centimeters: A length is a kind of value. 1m specifies a length. 1cm specifies a length scaled down by 100. gives us instead 1cm up to 21474836.47m, which is still enough to represent any possible distance on the Earth's surface. For instance, London to Sydney is about 17000000m. Left to itself, Inform choose the scaling for a unit so that it can represent exactly 1 of the smallest notation - so in our example Inform resolves down to 0.01m, not 1m, in order that it can represent 1cm accurately. But we can also fix the scaling ourselves: A length is a kind of value. 1m specifies a length scaled at 10000. Notice "scaled at", not "scaled down" or "scaled up" - this is now the first notation for length, so there's no existing notation which it could scale up or down. Anyway, now the range is 0.0001m, the width of a human hair, up to 214748.3647m, which is about 130 miles. (The Kinds index automatically keeps track of the range of values represented exactly.) Finally, for a really deluxe kind of value, we can also provide "equivalent" notations. The idea here is that we might want both miles and kilometers to work, even though they aren't direct scalings of each other. We can only do this approximately, but: 1 mile specifies a length equivalent to 1609m. Equivalent notations are never normally used in printing values back (but see the next section) - we wouldn't want Inform to print a sequence of values such as "1.6km", "1.65km", "1.056 miles", ... in an effort to be helpful. 14.6. Named notations When it has a variety of notations to choose from, Inform will normally use the neatest one given the size of the value it is printing. Suppose we've set up "weight", with three notations: A weight is a kind of value. 10kg specifies a weight. 1 tonne (singular) specifies a weight scaled up by 1000. 2 tonnes (plural) specifies a weight scaled up by 1000. Inform will then print back values like so: 45kg -> "45kg" 1000kg -> "1 tonne" 2500kg -> "2.5 tonnes" 80000kg -> "80 tonnes" Note the way Inform goes into decimal places in order to talk about 2500kg in terms of tonnes rather than kilograms - it is minimising the integer part of the unit, but trying to keep it non-zero. So Inform prefers "45kg" to "0.045 tonnes". Although Inform's habit of choosing the best notation available is usually just what we want, we sometimes want to make the choice ourselves. For instance, if we were printing out a table of different weights, we might want to give all of them in kilograms, whatever their size. In that case we can, if we want, give names to our different notations: 1 tonne (singular, in tonnes) specifies a weight scaled up by 1000. 2 tonnes (plural, in tonnes) specifies a weight scaled up by 1000. Now we could write, for instance: "The weighbridge warns you not to exceed [the maximum load in tonnes]." And the figure will always use tonnes now, even if Inform would normally think it odd: "The weighbridge warns you not to exceed 0.001 tonnes." But it will still correctly use "tonne" or "tonnes" as appropriate - what has changed is that instead of choosing from all of the weight notations, Inform now chooses from the notations labelled as "in tonnes". 14.7. Making the verb "to weigh" So now we can invent notations for weight. We could, for instance, write: Weight is a kind of value. 1kg specifies a weight. Every thing has a weight. And that allows us to write: The lead pig is in the Salt Mine. The weight of the lead pig is 45kg. But nobody would say it that way: they'd say "The lead pig weighs 45kg." So what we really need to complete our setup is a verb "to weigh". We have already created new verbs, but none of those methods are quite convenient for this. We want to relate something tangible (the lead pig) to something intangible (45kg), and there's no convenient relation to express this; if we set it up as a condition, we'd get something we couldn't assert, only test. Instead, we'll do something different this time: The verb to weigh (it weighs, they weigh, it is weighing) implies the weight property. Previous definitions like this ended "implies the ... relation", rather than "implies the ... property", but the idea is the same. The meaning of "X weighs Y" is that the weight property of X is equal to Y. So we can now write: A thing usually weighs 1kg. The lead pig weighs 45kg. something weighing 20kg if three things weigh 5kg, ... And as we saw in the chapter on Descriptions, we can also set up adjectives, comparatives and superlatives: Definition: A thing is heavy if its weight is 20kg or more. which creates "heavy", "heavier" and "heaviest". Example 247 (**): Dimensions This example draws together the previous snippets into a working implementation of the weighbridge. Example 248 (***): Lead Cuts Paper To give every container a breaking strain, that is, a maximum weight of contents which it can bear - so that to put the lead pig into a paper bag invites disaster. 14.8. The Metric Units extension To sum all of this up, what started out as a simple business of setting a notation for lengths becomes something quite elaborate when we try to match the actual notations used by scientists and engineers. It's all optional, of course, but as we want more and more of this, we might find ourselves with a spread of notations like this: 1mm ... 1cm ... 1m ... 1km and in addition we might want equivalents for the inch, the yard and the mile; and verbal forms like the meter and the millimeter, and then alternate spellings like the kilometre; and then both singular and plural forms. And that's just length - what about density, area, pressure, velocity and a dozen other physical quantifies? After a while these declarations start to look as vastly fussy as a box of presentation cutlery. Fortunately the whole set is indeed available in a presentation box, and at no extra charge. The built-in extension "Metric Units by Graham Nelson" sets up a whole range of scientific units, with all the notations we are likely to want, and scaled about right for human situations. Like the other built-in extensions, it has its own documentation and examples. 14.9. Notations including more than one number We've seen quite enough scientific notation for the time being. There are plenty of other notations used in natural language, for everyday concepts, where people don't use a tidy spread of powers of 10. Instead they use mixtures, with some sort of punctuation or text to divide them. For instance, the running time of a piece of music is easier to follow in minutes and seconds than in seconds alone: old-fashioned LP sleeves used to quote running times in the form 4'33. A running time is a kind of value. 3'59 specifies a running time. The choice of "3" here makes no difference, much as the choice of "10" in the weight examples was arbitrary. But the "59" is significant. Numbers after the first one are expected to range from 0 up to the value we quote - so in this case, the number of seconds can be anything from 0 to 59. Or, for instance: A height is a kind of value. 5 foot 11 specifies a height. A specification can contain up to four numbers like this, but once again we might need to worry about the maximum value which can be stored. For instance, using the 3'59 notation, we can only go up to 546'07 (if we're using the Z-machine format setting) - a little over 9 hours, so the new Tori Amos album will not be a problem, but some of the more punishing German operas might break the bank. Notations must not contain double-quotation marks because, even though people did once use these to denote minutes of arc, they would simply confuse programs like Inform's user interface which have to keep track of what is quoted text and what is not. But other punctuation marks are fine provided they occur between two digits. For instance, in A monetary value is a kind of value. $1.99 specifies a monetary value. the full stop between the 1 and the 99 is not interpreted as a division of two sentences; and similarly for colons in examples such as An aspect ratio is a kind of value. 16:9 specifies an aspect ratio. 14.10. The parts of a number specification We often need to break up a number specification into its pieces. For instance, suppose we want to know the dollars part of $1.99? We can do this by naming the parts: A monetary value is a kind of value. $1.99 specifies a monetary value with parts dollars and cents. We can now find the relevant parts like so. Suppose that "sum" is a monetary value. Then: dollars part of sum cents part of sum are both numbers, so for instance we can say "Looks like around [dollars part of sum in words] dollar[s]." We can also go the other way: monetary value with dollars part 4 cents part 72 produces the monetary value $4.72. (Note the lack of commas or "and"s, and that the parts have to be given in the right order.) This is really intended to be useful when we manipulate such values in unusual ways: An aspect ratio is a kind of value. 16:20 specifies an aspect ratio with parts width and height. To decide which aspect ratio is the wider version of (AR - an aspect ratio): let W be the width part of AR multiplied by 2; let H be the height part of AR; let the wider ratio be the aspect ratio with width part W height part H; decide on the wider ratio. Declaring the parts of a number specification individually also enables us to tack one or more options onto any of the parts: A monetary value is a kind of value. $1.99 specifies a monetary value with parts dollars and cents (optional, preamble optional). This declares that the "cents" part is optional - it will be 0 if not specified - and that if omitted, the non-numeric "preamble" before it should also be omitted. Thus "$3" is now valid and equivalent to "$3.00": indeed it will be the preferred form when Inform prints out a monetary value which is an exact number of dollars. If we had said that "cents" was optional, but not said that the preamble was optional, then "$3." would have been the form - which is less satisfactory. There is only one other option: "without leading zeros", as in the following. An aspect ratio is a kind of value. 16:20 specifies an aspect ratio with parts width and height (without leading zeros). This ensures that when the ratio 4:3 is printed, it will be printed as "4:3" and not "4:03" as would otherwise happen. Example 249 (***): Zqlran Era 8 Creating an alternative system of time for our game, using new units. 14.11. Understanding specified numbers It may be worth noting in passing that number specifications, like all other kinds of value, can be understood in typed commands. (See the chapter on Understanding for more on what can go in such square brackets.) For instance: "America Stands Tall" The Oval Office is a room. Josh and Toby are men in the Oval. A height is a kind of value. 5 foot 11 specifies a height. A person has a height. Josh is 5 foot 8. Toby is 5 foot 10. Height guessing is an action applying to one thing and one height. Understand "guess [someone] is [height]" as height guessing. Check height guessing: if the noun is not a person, say "You can only guess the height of people." instead. Carry out height guessing: if the height of the noun is the height understood, say "Spot on!"; if the height of the noun is greater than the height understood, say "No, [the noun] is taller than that."; if the height of the noun is less than the height understood, say "No, [the noun] is shorter than that." Test me with "guess josh is 6 foot 3 / guess josh is 5 foot 9 / guess josh is 5 foot 3 / guess josh is 5 foot 8". Example 250 (***): Snip A string which can be cut into arbitrary lengths, and then tied back together. 14.12. Totals This chapter began by mentioning arithmetic, and then went on a long diversion to create scientific units, everyday weights and measures, and other notational conveniences. Putting all of that together, it's time now to calculate something with all of these numerical quantities. Suppose we invent the idea of weight, and give everything a weight of its own. Most items will have a nominal weight of 1kg, but people will be heavier. Going on actuarial tables, we might say: A weight is a kind of value. 10kg specifies a weight. Everything has a weight. A thing usually has weight 1kg. A man usually has weight 80kg. A woman usually has weight 67kg. Definition: A thing is light if its weight is 3kg or less. Definition: A thing is heavy if its weight is 10kg or more. and this provides us with "lighter", "lightest", "heavier" and "heaviest" as before. Now we could say "if Peter is heavier than Paul", or even "if Peter is heavier than 75kg", and so forth. We need one more tool:

total (arithmetic values valued property) of (description of values) ... value
This phrase produces the total of some property held by all of the values matching the description. A problem message is produced if the values in question can't have that property ("the total carrying capacity of scenes"), or if it holds a kind of value which can't meaningfully be added up ("the total description of open doors"). Example: total carrying capacity of people in the Deep Pool
That gives us everything we need for a working balance platform: The balance platform is a supporter in the Weighbridge. "The balance platform is currently weighing [the list of things on the platform]. The scale alongside reads: [total weight of things on the platform]." Note that this only works because we said that "everything has a weight": otherwise it would make no sense to add up the weights of things. This enables us to get the average weight of a group of things, too: the total weight of things on the platform divided by the number of things on the platform But we should be careful that this does not accidentally divide by zero, which it will if the platform has nothing on it! As well as the average, we could find the maximum and minimum weights: the weight of the heaviest thing on the platform the weight of the lightest thing on the platform We should remember that "the heaviest thing on the platform" may be ambiguous, because there may be several equally heavy things there. That means if the lead pig is the heaviest thing on the platform will only reliably work if there is no possibility of a tie. A safer bet is: if the lead pig is the weight of the heaviest thing on the platform Example 251 (***): Nickel and Dimed A more intricate system of money, this time keeping track of the individual denominations of coins and bills, specifying what gets spent at each transaction, and calculating appropriate change. 14.13. Equations Forming totals is all very interesting in its way, but it's book-keeping rather than physics. As a glance at any school science textbook shows, the way to apply physics is to work out an unknown quantity - say, the time taken for a dropped ball to hit the ground - by combining known quantities into an equation - the height it is dropped from, and the strength of gravity. It's a convention centuries old now that textbooks and research papers never describe these equations in running text. Even for simple formulae, we like to write "F=ma", not "let the force be the mass times the acceleration". And the standard way to print this is to break off and display an equation, not to squeeze it into the text as if it were ordinary verbiage. Just as Inform's Tables imitate those in printed books (see the next chapter), so its Equations do. In this section, we'll use a combination of three equations to work out how soon and how hard an object pushed off a table will hit the floor. First, we'll include Metric Units, to define all of the kinds of value and notations we need. Include Metric Units by Graham Nelson. Now we'll give everything a mass (Metric Units likes to talk about mass instead of weight, but on Earth it's the same thing) and also set up a typical strength for gravity - it's a little less at the poles, a little more at the equator, but this is the conventional approximate value to use. The acceleration due to gravity is an acceleration that varies. The acceleration due to gravity is usually 9.807 m/ss. A thing has a mass. The mass of a thing is usually 10g. To a Renaissance scientist, typically living in a walled European town, a cannon ball was a familiar thing, and it often featured in imaginary experiments: Laboratory is a room. The cannon ball is in the Laboratory. "A cannon ball perches delicately on a lab bench." The mass of the cannon ball is 2kg. And now we're ready for the three equations. These will all have names, but we could just as easily have numbered them, calling them (say) ``Equation 1'', ``Equation 2'' and ``Equation 3''. Equation - Newton's Second Law F=ma where F is a force, m is a mass, a is an acceleration. Equation - Principle of Conservation of Energy mgh = mv^2/2 where m is a mass, h is a length, v is a velocity, and g is the acceleration due to gravity. Equation - Galilean Equation for a Falling Body v = gt where g is the acceleration due to gravity, v is a velocity, and t is an elapsed time. An equation has to take the form of one formula equals another, where each formula is made up from symbols defined afterwards. The symbols can be defined as definite values (as "g" is defined in the Galilean Equation), or just by telling Inform their kinds of value (as "v" and "t" are defined). Equations are read using standard mathematical conventions. So "x + yz" means that we multiply y and z, then add that to x; "ab/cd" divides the product of a and b by the product of c and d. Multiplication signs can be omitted, just as science books normally do (though we can always write them if we want to, using the asterisk *, as usual in computing). The need for brackets is minimised, with any luck, but we can use them if we need to: "x(y+ab)" is legal, for instance. Here is the calculation: Instead of pushing the cannon ball: let the falling body be the cannon ball; let m be the mass of the falling body; let h be 1.2m; let F be given by Newton's Second Law where a is the acceleration due to gravity; let v be given by the Principle of Conservation of Energy; let t be given by the Galilean Equation for a Falling Body; say "You push [the falling body] off the bench, at a height of [h], and, subject to a downward force of [F], it falls. [t to the nearest 0.01s] later, this mass of [m] hits the floor at [v]."; now the falling body is in the location. And the result is: You push the cannon ball off the bench, at a height of 1.2m, and, subject to a downward force of 19.614N, it falls. 0.49s later, this mass of 2kg hits the floor at 4.85 m/s. Not all that fast-moving - it's only about 10 mph, ten times slower than one fired by a Renaissance cannon - but half a second wouldn't give you long to get your foot out of the way. How was that done? The crucial lines are the ones in the form "let X be given by E...", which is a new form of "let".

let (a name not so far used) be given by (equation name)
or: let (a temporary named value) be given by (equation name)
This phrase creates a new temporary variable, starting it with the value found by solving the given equation. The variable lasts only for the present block of phrases, which certainly means that it lasts only for the current rule. Example: let F be given by Newton's Second Law where a is the acceleration due to gravity; There is also a more compact syntax, giving the equation explicitly: let KE be given by KE = mv^2/2 where KE is an energy;
When we solve with "let", then, all of the other symbols should either already have values (because they exist as "let" values already made) or else be specified in the line. For instance, let F be given by Newton's Second Law where a is the acceleration due to gravity; is allowed because "F" is one of the symbols in "F = ma"; of the other two symbols, we have a "let" variable called "m" already - it's the mass of the cannon ball - and we declare exactly what "a" is. The next calculation is more interesting: let v be given by the Principle of Conservation of Energy; Since the equation here is "mgh = mv^2/2", Inform has to do some algebra to work out "v" in terms of the other unknowns - it's the square root of 2gh, but we don't need to work that out. Inform can't always solve implicit equations - for instance, it can't deduce "m" from this equation - but it's correct on all the easy cases which occur in basic physics, and that enables us to write equations in their most natural form, which is easier to read and understand. The advantage of setting out an equation formally is that it can be used in many places - we could use Newton's Second Law again for something quite different, for example. But it's a little cumbersome for something simple which we only need once, so this is neater: let KE be given by KE = mv^2/2 where KE is an energy; Here the equation is written out explicitly instead of being named, but otherwise everything works in the same way. Example 252 (*): Widget Enterprises Allowing the player to set a price for a widget on sale, then determining the resulting sales based on consumer demand, and the resulting profit and loss. 14.14. Arithmetic with units The example equations in the previous section carried out quite a lot of arithmetic, but they may have given the impression that Inform always allows arithmetic - which is not true. This is actually a good thing, because it keeps us from error. For instance, Inform will not allow: Equation - Newton's Totally Bogus Law F = m^2 where F is a force, m is a mass. because whatever you get when you square a mass, you don't get a force - in the same way that a length times another length makes an area, not another length. Physicists call this "dimensional analysis", and it often provides clues about which equations are right. Just after the Second World War, someone correctly worked out the explosive power of an atomic bomb without any classified information simply by guessing what values would appear in the formula, and then finding the simplest equation they could appear in. In general, Inform will not allow numerical kinds of value to be multiplied or divided by each other (or square or cube rooted) unless we give it instructions that this would make sense. Of course, there's plenty we can still do without any need for such instructions. For instance, going back to weight, The Weighbridge is a room. "A sign declares that the maximum load is [100kg multiplied by 3]." ...will produce the text "A sign declares that the maximum load is 300kg." Here Inform knows that it makes sense to multiply a weight by 3, and that the result will be a weight. Similarly, Inform allows us to add and subtract weights, and several different forms of division are allowed: The blackboard is in the Weighbridge. "A blackboard propped against one wall reads: '122 / 10 is [122 divided by 10] remainder [remainder after dividing 122 by 10]; but 122kg / 10kg is [122kg divided by 10kg] remainder [remainder after dividing 122kg by 10kg]; and 122kg / 10 is [122kg divided by 10] remainder [remainder after dividing 122kg by 10].'" When we visit the Weighbridge, we find: A blackboard propped against one wall reads: "122 / 10 is 12 remainder 2; but 122kg / 10kg is 12 remainder 2kg; and 122kg / 10 is 12kg remainder 2kg." Whereas we are not allowed to divide 122 by 10kg: that would make no sense, since 122 is a number and not made up of kilograms. Inform will produce a problem message if we try. Similarly, Inform won't normally allow us to multiply two weights together - but see the next section. Example 253 (*): Frozen Assets A treatment of money which keeps track of how much the player has on him, and a BUY command which lets him go shopping. Example 254 (**): Money for Nothing An OFFER price FOR command, allowing the player to bargain with a flexible seller. Example 255 (***): Lemonade Containers for liquid which keep track of how much liquid they are holding and of what kind, and allow quantities to be moved from one container to another. Example 256 (***): Savannah Using the liquid implementation demonstrated in Lemonade for putting out fires. 14.15. Multiplication of units To recap, then, it is forbidden to multiply 122kg and 10kg, not because it could never make sense (a scientist might occasionally multiply two weights) but because the result is - what? Not a number, and not a weight any more. But we are allowed to tell Inform what the result ought to be, and once we have done so, the multiplication will be allowed: A length is a kind of value. 10m specifies a length. An area is a kind of value. 10 sq m specifies an area. A length times a length specifies an area. The balance platform is in the Weighbridge. "The balance platform is 10m by 8m, giving it an area of [10m multiplied by 8m]." which will turn up as: The balance platform is 10m by 8m, giving it an area of 80 sq m. And having told Inform that lengths multiply to area, we could also divide an area by a length to get a length: no further instructions would be needed. The built-in "Metric Units" extension includes all of the standard ways that physical quantities are multiplied, and a good way to see these is to try out one of the Metric Units examples and look at the Kinds index, which includes a table showing how all of this works. Example 257 (*): Depth Receptacles that calculate internal volume and the amount of room available, and cannot be overfilled. Example 258 (**): Fabrication A system of assembling clothing from a pattern and materials; both the pattern and the different fabrics have associated prices. Example 259 (**): The Speed of Thought Describing scientifically-measured objects in units more familiar to the casual audience. 14.16. Review of Chapter 14: Numbers and Equations 1. Numbers numbers may be manipulated by arithmetic with the forms either spelled out or represented as symbols: the score + 10 100 - the score 10 * 21 144 / 12 the score plus 10 100 minus the score 10 times 21 10 multiplied by 21 144 divided by 12 We may change numbers that vary using "change" or "now"; the short hand "increase... by..." and "decrease... by..." allow us to do addition and subtraction a little more efficiently, as well: now the score is the score plus 10; increase the score by 10; decrease the score by 10. 2. New numerical kinds of value ("units") can be specified like this: A weight is a kind of value. 10kg specifies a weight. There can be multiple notations for the same kind of value, with different relative scalings: A weight is a kind of value. 10kg specifies a weight. 1 tonne specifies a weight scaled up by 1000. 1g specifies a weight scaled down by 1000. There can be equivalents on a different scale altogether: 1 ounce specifies a weight equivalent to 0.028kg. 1 pound specifies a weight equivalent to 16 ounce. We can also mark some notations as singular or plural, and give them names: 1 tonne (singular, in tonnes) or 2 tonnes (plural, in tonnes) specifies a weight scaled up by 1000. This enables us to say "[weight of the tank in tonnes]", for instance. Alternatively, we can give notations combining several scales in one: Price is a kind of value. $1.99 specifies a price. [default $0.00] Price is a kind of value. $1.99 specifies a price with parts dollars and cents. Price is a kind of value. $1.99 specifies a price with parts dollars and cents (optional, preamble optional). An aspect ratio is a kind of value. 16:20 specifies an aspect ratio with parts width and height. If we define a unit with parts, we may then refer to these parts separately: dollars part of the price of the apple cents part of the price of the apple Once a unit has been defined, we can understand this unit in the player's input. Understand "sell [something] for [price]" as selling it for. (For more about Understand sentences, see the chapter on Understanding.) 4. We can also perform arithmetic on units, and tell Inform how multiplication turns units into other units: the total weight of things on the platform divided by the number of things on the platform if the price understood is less than $0.50... if the price of the apple is more than $5.00, ... decrease the price of the apple by $0.50 A length times a length specifies an area. Chapter 15: Tables 15.1. Laying out tables When printed books need to display detailed information in a systematic way, they break off from running text and print a table instead. Inform does the same. Here is a typical example: Table 2.1 - Selected Elements Element Symbol Atomic number Atomic weight "Hydrogen" "H" 1 1 "Iron" "Fe" 26 56 "Zinc" "Zn" 30 65 "Uranium" "U" 92 238 After the two titling lines, each line represents one row in the table, and entries on a line must be separated by at least one tab character. A table must occupy a single whole paragraph, with no skipped lines or missing entries. The top line is a title, the first word of which must be the word 'Table'. We can then either give a table number (this need not actually be a number: Table C2, or some such, would be fine), or give a name, or both - as in this case. The possible titling formats are: Table 2.3 Table of Population Statistics Table 2.3 - Population Statistics In the last example we could call the table either "Table 2.3" or "Table of Population Statistics". Each column then has a name, and the contents must all be the same kind of value. In the elements table the "Symbol" column contains only text, for instance, and the "Atomic weight" column contains only numbers. Any kinds of value will do, so long as all the entries in the column are mutually compatible. (For instance, mixing rooms and things in a single column would be fine, as these can be reconciled, but mixing numbers and rooms would not.) 15.2. Looking up entries The simplest way to access the information inside tables is to ask explicitly for it, specifying the row number, the column name and what table is to be consulted. So, given our example table Table 2.1 - Selected Elements Element Symbol Atomic number Atomic weight "Hydrogen" "H" 1 1 "Iron" "Fe" 26 56 "Zinc" "Zn" 30 65 "Uranium" "U" 92 238 we can write the following description: symbol in row 3 of the Table of Selected Elements to produce the value "Zn". Or the following will run off some chemical data: repeat with N running from 1 to the number of rows in the Table of Selected Elements: say "The atomic weight of [element in row N of the Table of Selected Elements] is [atomic weight in row N of the Table of Selected Elements]." The result of which will be: The atomic weight of Hydrogen is 1. The atomic weight of Iron is 56. The atomic weight of Zinc is 65. The atomic weight of Uranium is 238. Note that the first row in a table is row number 1, and that the last can be found with the phrase:

number of rows in/from (table name) ... number
This phrase produces the number of rows (including any blank rows) in the given table. Example: number of rows in the Table of Selected Elements
15.3. Corresponding entries Continuing our example of the elements: Table 2.1 - Selected Elements Element Symbol Atomic number Atomic weight "Hydrogen" "H" 1 1 "Iron" "Fe" 26 56 "Zinc" "Zn" 30 65 "Uranium" "U" 92 238 If we want to know the atomic number of Uranium, say, it seems artificial to have to talk about the particular row number where the information happens to be. So we are also allowed to cross-reference, like so: the atomic number corresponding to a symbol of "Fe" in the Table of Selected Elements This results in 26, and similarly the symbol corresponding to an atomic number of 26 in the Table of Selected Elements results in "Fe". But we have to be careful: the element corresponding to an atomic number of 27 in the Table of Selected Elements This is not allowed (it produces an error at run-time), because there is no row with atomic number 27 in this rather limited table. We can check this in advance with the condition: if there is an element corresponding to an atomic number of 27 in the Table of Standard Elements ... Or more simply: if there is an atomic number of 27 in the Table of Standard Elements ... The condition "if there is..." can be used with any reference to a table entry: for instance, "if there is a symbol in row 5 of the Table of Standard Elements" would be false, because there are only four rows. Example 260 (***): Dubai An elevator which connects any of 27 floors in a luxury hotel. 15.4. Changing entries Here is another rather definitive, immutable-looking table: Table 4 - Recent Monarchs Name Accession Family "Anne" 1702 Stuart "George I" 1714 Hanover "George II" 1720 Hanover "George III" 1760 Hanover "George IV" 1820 Hanover "William IV" 1830 Hanover "Victoria" 1837 Hanover "Edward VII" 1901 Saxe-Coburg-Gotha "George V" 1910 Windsor "Edward VIII" 1936 Windsor "George VI" 1936 Windsor "Elizabeth II" 1952 Windsor But table entries can be changed as freely as variables: that is, any value can be entered so long as it has the right kind. We cannot put a dynasty into the "Name" column, or text in the "Accession" column. The phrase needed is "change ... to ...", just as it is for properties or variables: Dynasty is a kind of value. The dynasties are Stuart, Hanover, Saxe-Coburg-Gotha and Windsor. The Table Office is a room. The Succession is in the Table Office. "The Succession, a ponderous list of English monarchs, takes pride of place." Instead of examining the Succession: say "The Succession List runs as follows..."; repeat with N running from 1 to the number of rows in the Table of Recent Monarchs: say "[accession in row N of Table 4]: [name in row N of Table 4] ([family in row N of Table 4])." Instead of attacking the Succession: now the family corresponding to an accession of 1720 in the Table of Recent Monarchs is Stuart; now the name in row 4 of the Table of Recent Monarchs is "Graham I"; now the name in row 5 of the Table of Recent Monarchs is "Trixibelle IV"; say "You deface the English succession, making suitable amendments with a quill pen. Considering it is supposed to be mightier than the sword the effect is a little disappointing." Test me with "examine succession / attack it / examine it". 15.5. Choosing rows The following would be one way to print out a list of recent Kings and Queens: To list the succession: say "The Succession List runs as follows..."; repeat with N running from 1 to the number of rows in the Table of Recent Monarchs: say "[accession in row N of the Table of Recent Monarchs]: [name in row N of the Table of Recent Monarchs] ([family in row N of the Table of Recent Monarchs])." This works, but is repetitive. We often want to work on a single row for a while, either to change things or think about the contents, and it is tiresome to keep specifying the row over and over again. The following shorthand provides some relief:

choose a/the/-- row (number) in/from (table name)
This phrase selects the row with the given number. Row numbers in a table start from 1, so choose row 1 from the Table of Recent Monarchs selects the top row.
That allows us to improve the loop: To list the succession: say "The Succession List runs as follows..."; repeat with N running from 1 to the number of rows in the Table of Recent Monarchs: choose row N in the Table of Recent Monarchs; say "[accession entry]: [name entry] ([family entry])."; Actually, as we'll see in the next section, this kind of loop is needed so often that there's a shorthand wording for it. Note that since "accession" is a column name, "accession entry" means the entry in that column of the currently chosen row. This notation can only be used if a "choose" has certainly already happened, and it is a good idea to make that choice somewhere close by in the source code (and certainly in the same rule or phrase definition) for the sake of avoiding errors. We can also choose rows by specifying something about them, like so:

choose a/the/-- row with (table column) of (value) in/from (table name)
This phrase selects the first row, working down from the top of the given table, in which the given column has the given value. Example: choose row with a name of "Victoria" in the Table of Recent Monarchs; A run-time problem message is produced if the value isn't found anywhere in that column.
Sometimes it will happen that a column's name clashes with the name of something else: for instance, if we call a column "apples" but we also have a kind called "apple", so that the word "apples" could mean either some fruit or the column. Inform will generally prefer the former meaning as more likely. In case of such trouble, we can simply refer to "the apples column" rather than just "the apples": for instance, "choose row with an apples column of..." rather than "choose row with an apples of..." We can also choose a row quite at random:

choose a/the/-- random row in/from (table name)
This phrase makes a uniformly random choice of rows in the given table. Note that a table always has at least one row, so this can't fail.
15.6. Repeating through tables We very often want to run through a table doing something to, or with, each row in turn, so a special loop is provided for this. Rather than having to write all this out: To list the succession: say "The Succession List runs as follows..."; repeat with N running from 1 to the number of rows in the Table of Recent Monarchs: choose row N in the Table of Recent Monarchs; say "[accession entry]: [name entry] ([family entry])." We can simply use this instead:

repeat through (table name):
This phrase causes the block of phrases following it to be repeated once for each row in the given table, choosing each row in turn, from top to bottom. Blank rows are skipped. Example: To list the succession: say "The Succession List runs as follows..."; repeat through the Table of Recent Monarchs: say "[accession entry]: [name entry] ([family entry])."
Note that there is no loop variable here, unlike in other forms of "repeat", because it's the choice of row which keeps track of how far we have got. We can alternatively go backwards:

repeat through (table name) in reverse order:
This phrase causes the block of phrases following it to be repeated once for each row in the given table, choosing each row in turn, from bottom to top. Blank rows are skipped.
More often we want a sequence which is neither forwards nor backwards, but which depends on the actual values in the table.

repeat through (table name) in (table column) order:
This phrase causes the block of phrases following it to be repeated once for each row in the given table, choosing each row in turn, in order of the values in the given column. Blank rows are skipped. Example: repeat through the Table of Recent Monarchs in name order: ... repeat through the Table of Recent Monarchs in accession order: ... work through the same table in rather different orders. The sequence is lower to higher (small numbers to high numbers, A to Z, and so on); insert "reverse" after "in" to reverse this.

repeat through (table name) in reverse (table column) order:
This phrase causes the block of phrases following it to be repeated once for each row in the given table, choosing each row in turn, in order of the values in the given column. Blank rows are skipped. Example: repeat through the Table of Recent Monarchs in reverse name order: ... repeat through the Table of Recent Monarchs in reverse accession order: ... work through the same table in rather different orders. The sequence is higher to lower (high numbers to small numbers, Z to A, and so on); delete the "reverse" after "in" to reverse this.
In a loop like this, the data is not searched very efficiently, which is fine for modest-sized tables like the examples in this chapter, but might be a problem for much larger tables: see the later section on sorting. These definitions mentioned blankness several times, and that's the topic to cover in the next section. (See Sorting for reordering a table to put it into increasing or decreasing order of the entries in any column.) Example 261 (**): Port Royal 4 A cell window through which the player can see people who were in Port Royal in the current year of game-time. 15.7. Blank entries We are allowed to leave certain entries blank (perhaps to be filled in later, perhaps not) by writing "--" instead of the relevant value: Table 2.1 - Selected Elements Element Symbol Atomic number Atomic weight "Hydrogen" "H" 1 1 "Iron" "Fe" -- 56 "Zinc" -- 30 65 "Uranium" "U" 92 238 In effect, blank entries don't exist. "--" is not a value, but only a hole where a value might be. It can be useful to check for this:

if there is (a table entry):
This condition is true if the entry referred to exists, that is, that is, the space for it in the table is not blank. Examples: if there is a symbol corresponding to an atomic number of 30 in the Table of Standard Elements ... if there is an atomic number in row 2 of the Table of Standard Elements ...

if there is no (a table entry):
This condition is true if the entry referred to does not exist, that is, the space for it in the table is blank. Examples: if there is no symbol corresponding to an atomic number of 30 in the Table of Standard Elements ... if there is no atomic number in row 2 of the Table of Standard Elements ...
15.8. Blank columns An entire column of blank entries "--" is problematic: Table 2 - Selected Elements Element Symbol Atomic number Atomic weight "Hydrogen" "H" 1 -- "Iron" "Fe" 26 -- "Zinc" "Zn" 30 -- "Uranium" "U" 92 -- Inform is unable to work out what kind of value should go into the "atomic weight" column here, since it has no examples to guess from. We can get around this by writing in the name of a kind of value: Table 2 - Selected Elements Element Symbol Atomic number Atomic weight "Hydrogen" "H" 1 a number "Iron" "Fe" 26 -- "Zinc" "Zn" 30 -- "Uranium" "U" 92 -- That top entry in the "atomic weight" column is also blank, but now Inform knows that anything put into the column in future will be a number. If there are many rows, and perhaps several blank columns, it would become very tedious to have to keep typing out "--". So this is optional at the end of a row: it remains compulsory for a blank value appearing in between two values which aren't blank. This is the general idea: Table 2 - Selected Elements Element Symbol Atomic number Density Specific gravity "Hydrogen" "H" 1 a number a number "Iron" "Fe" 26 "Zinc" "Zn" 30 "Uranium" "U" 92 15.9. Blank rows There is no difficulty about entirely blank rows: or rather, the only difficulty is once again that they are boring to type out. We can avoid the necessity by appending "with ... blank rows" at the foot of the table: Table 2 - Selected Elements Element Symbol Atomic number Atomic weight "Hydrogen" "H" 1 a number "Iron" "Fe" 26 -- "Zinc" "Zn" 30 -- "Uranium" "U" 92 -- with 3 blank rows (These words cannot be placed in between rows, but only at the bottom.) And indeed the table can start out completely empty: Table 3 - Undiscovered Periodic Table Element (text) Symbol (text) Atomic number (a number) Atomic weight (a number) with 92 blank rows Blank rows are useful because they enable us to add new data to a table. In effect, they are invisible when not used. A repeat loop like repeat through Table 3: ... automatically skips blank rows, so it would initially do nothing at all. Similarly, choosing a "random" row will never choose a blank one. A convenient way to test if a table contains non-blank rows is to use the built-in adjectives "empty" and "non-empty". So: if the Undiscovered Periodic Table is empty, ... tests whether all of its rows are blank; if even one cell contains a value then the table is "non-empty". Example 262 (*): If It Hadn't Been For... A sound recording device that records the noises made by player and non-player actions, then plays them back on demand. 15.10. Adding and removing rows Writing in new rows is simple, once we can find space for them:

choose a/the/-- blank row in/from (table name)
This phrase chooses a row in the given table which is currently blank under every column. A run-time problem message is issued if no rows are blank. Example: choose a blank row in Table 3; now element entry is "Fluorine"; now symbol entry is "F"; now atomic number entry is 9; now atomic weight entry is 19;
To avoid problem messages, it can be important to worry about free space. To that end we can not only find the number of rows (as we have already seen) but also the number currently blank and not blank:

number of blank rows in/from (table name) ... number
This phrase produces the number of rows in the given table which are entirely blank (that is, blank under every column).

number of filled rows in/from (table name) ... number
This phrase produces the number of rows in the given table which are not entirely blank (that is, at least one column has a value in this row).
"Filled" here really means "non-blank": a row can be filled in this sense even if only one of its values exists. Since every row is either blank or filled, it must be true that: the number of blank rows in Table 3 the number of filled rows in Table 3 add up to "the number of rows in Table 3". We've seen that blank entries can be filled with values using "now": now symbol entry is "F"; But the same method can't be used to put blanks back, since a blank is not a value. Instead:

blank out (a table entry)
This phrase replaces the entry referred to with a blank, erasing any value previously stored there. Example: choose row 1 in the Table of Fish Habitats; blank out the salinity entry;
These more destructive phrases need a steady hand:

blank out the whole row
This phrase replaces the currently chosen row with blanks, erasing any value previously stored under any of the columns. Example: choose row 1 in the Table of Fish Habitats; blank out the whole row;

blank out the whole (table column) column in (table)
This phrase replaces the currently chosen column with blanks, erasing any value previously stored in any of the rows. Example: blank out the whole salinity column in the Table of Fish Habitats;

blank out the whole of (table)
This phrase replaces every row of the currently chosen table with blanks, erasing any value previously stored anywhere in it. Example: blank out the whole of the Table of Fish Habitats; This is only really useful when a Table is being used to hold working space for some calculation or other.
(Beta release note) Previous builds allowed the following:

delete (a table entry)
This phrase is now deprecated, and is exactly equivalent to the preferred form, blank out (table entry)
Example 263 (**): Odyssey A person who follows a path predetermined and stored in a table, and who can be delayed if the player tries to interact with her. 15.11. Sorting The three ways to sort a table exactly correspond to the three different orders in which tables can be repeated through. First:

sort (table name) in random order
This phrase rearranges the rows of the given table so that the non-blank rows occur at the top, in a uniformly random order, and any blank rows at the bottom. Example: sort the Table of Recent Monarchs in random order;
Secondly:

sort (table name) in (table column) order
This phrase rearranges the rows of the given table so that the non-blank rows occur at the top, so that the given column has ascending order, and any blank rows at the bottom. Example: sort the Table of Recent Monarchs in accession order; Ascending order means 1 up to 10, say, or A up to Z, with blank values coming last.

sort (table name) in reverse (table column) order
This phrase rearranges the rows of the given table so that the non-blank rows occur at the top, so that the given column has descending order, and any blank rows at the bottom. Example: sort the Table of Recent Monarchs in reverse name order; Descending order means 10 down to 1, say, or Z down to A, with blank values coming last.
Note that blank values will always be placed below non-blank ones, and entirely blank rows last of all. This is true even if we use "reverse". The method of sorting is "stable", that is, if two rows have the same value then they will stay the same way round in the sorted table, rather than being swapped over. Example 264 (**): Jokers Wild A deck of cards which can be shuffled and dealt from. 15.12. Listed in... Tables are especially useful for combining a run of basically similar rules in a simple and concise way. The "listed in" condition, as in if the newfound object is an item listed in the Table of Treasures... looks through a given table (here "table of treasures"), in a given column ("item"), to see if a given value is present ("the newfound object"). If this is successful, the row where it was found is automatically chosen. We can similarly use "... listed in ..." in a description used when specifying an action. Thus: After taking an item listed in the Table of Treasures: if there is no time entry: now the time entry is the time of day; increase the score by the value entry; say "Taken!" This assumes a table in the following shape: Table of Treasures Item Value Time brooch 5 a time tiara 8 -- coronet 10 -- In effect the table has allowed us to combine three very similar rules into one. The time column records the first time at which the item has been picked up, which starts out blank since at the start of play it has never been picked up. This enables us to award the appropriate number of points on the first occasion only. Example 265 (***): Noisy Cricket Implementing liquids that can be mixed, and the components automatically recognized as matching one recipe or another. 15.13. Topic columns When double-quoted matter appears in a column of a table, Inform will normally treat that as text for printing out. The exception is when the column is called "topic", where it is treated as text for comparing against what the player has typed. There is really only one operation allowed with topic columns, the "...listed in..." construction, but fortunately it is the one most often needed. Let us suppose that the Sybil has a penchant for telling passers-by which is the Greek muse for what. We might write: After asking the Sybil about a topic listed in the Table of Sybil's Replies, say "The Sybil declaims for a while, the gist being that the muse in question looks after [muse entry]." We can then provide a simple table giving her responses: Table of Sybil's Replies Topic Muse "calliope" "epic poetry" "clio" "history" "erato" "love poetry" "euterpe" "music" "melpomene" "tragedy" "polyhymnia" "sacred poetry" "terpsichore" "dancing" "thalia" "comedy" "urania" "astronomy" "monica" "tidiness" "phoebe" "massage" "rachel" "oval hair-cuts" Topics can use the full range of abilities of the "understanding" system which Inform uses to parse text, and which will be the subject of a later chapter. For now, note that the Sybil's topics might equally include "flora/eve" (matching the single word "flora" or the single word "eve"), or something more elaborate such as: "Bridget" or "Bridge" or "Bridget Jones" (See Understand for the system Inform uses to parse text.) Example 266 (*): Merlin A REMEMBER command which accepts any text and looks up a response in a table of recollections. Example 267 (***): Questionable Revolutions An expansion on the previous idea, only this time we store information and let characters answer depending on their expertise in a given area. Example 268 (***): The Queen of Sheba Allowing the player to use question words, and using that information to modify the response given by the other character. 15.14. Another scoring example To record (T - text) as achieved: choose row with a citation of T in the Table of Tasks Achieved; if there is no time entry: now time entry is the time of day; increase the score by the points entry. The phrase above expects to see a table like this one: Table of Tasks Achieved Points Citation Time 1 "pride" a time 3 "anger" 2 "avarice" 4 "envy" 1 "lust" 2 "gluttony" 3 "sloth" The middle column records the tasks to be achieved, the first column records the points on offer for each: the final column, initially blank, will store the times at which the tasks are first achieved. Before eating, record "gluttony" as achieved. The first time we record "gluttony" as achieved, 2 points will be awarded and the time will be logged in the Table, but on all subsequent occasions nothing will happen. So the combination of the phrase and the Table will look after a scoring system based on achieving specific goals (probably not the seven deadly sins, of course). We can, if we choose, use the same system to display a log of recent accomplishments: repeat through the Table of Tasks Achieved in reverse time order: say "[time entry]: [citation entry] ([points entry])." Example 269 (***): Goat-Cheese and Sage Chicken Implementing a FULL SCORE command which lists more information than the regular SCORE command, adding times and rankings, as an extension of the example given in this chapter. 15.15. Varying which table to look at So far, we have always used fixed table names when referring to tables: for instance in source like "sort the Table of Recent Monarchs in accession order", we refer to the "Table of Recent Monarchs", a definite and explicitly named table. With a little care, however, we are allowed to have variables which themselves hold the names of tables. This opens up the possibility of more elaborate ways of storing and interconnecting information in table form, but is probably best avoided until it becomes necessary. For example, suppose we have two different tables with the same basic structure: Table 1 - Nifty Opening Plays in US Scrabble word score "muzjiks" 128 Table 2 - Nifty Opening Plays in UK Scrabble word score "quartzy" 126 "squeezy" 126 We could then record which one of these tables to use in a variable: The lexicon is a table name that varies. The lexicon is Table 1. Note that for this purpose, the kind of value is a special kind called "table name", not "table". (The word "table" already has too many meanings and we must be careful to avoid ambiguities here.) We could make use of this as follows, for instance: To flip tables: say "You exchange dictionaries, lexically crossing the Atlantic. "; if the lexicon is Table 1, now the lexicon is Table 2; otherwise now the lexicon is Table 1; choose a random row in the lexicon; say "Did you know that according to [the lexicon], [word entry] scores [score entry]?" which produces text such as You exchange dictionaries, lexically crossing the Atlantic. Did you know that according to Table 1 - Nifty Opening Plays in US Scrabble, muzjiks scores 128? Example 270 (**): Farewell People who respond to conversational gambits, summarize what they said before if asked again, and provide recap of conversation that is past. 15.16. Defining things with tables Suppose we need to create a collection of items which differ in their properties, but are basically part of a larger pattern. For instance, here we set up what we need to make a collection of coloured shirts: A jersey is a kind of thing. A jersey is wearable. A jersey has a number called year established. A jersey has a text called citation. The description of a jersey is "Since [year established], the Tour de France has awarded this jersey to the [citation]." Now we have the pattern, but making the actual shirts is tedious and repetitive: The yellow jersey is a jersey. The year established of the yellow jersey is 1919. The citation of the yellow jersey is "race leader". The polkadot jersey... And so on. Instead, we can use a table to abbreviate all of this: "Tour des Maillots" The Staging Area is a room. A jersey is a kind of thing. A jersey is wearable. Some jerseys in the Staging Area are defined by the Table of Honorary Jerseys. The description of a jersey is "Since [year established], the Tour de France has awarded this jersey to the [citation]." Table of Honorary Jerseys jersey year established citation a yellow jersey 1919 "race leader" a polkadot jersey 1933 "King of the Mountains" a green jersey 1953 "highest point scorer on sprints" a white jersey 1975 "best cyclist aged 25 or less" The first column provides names for the new things to be created. Subsequent columns provide property values. Note that we did not need to say that jerseys have a number called "year established" because Inform is able to infer this from the column heading and the presence of numbers in the column; similarly for "citation". Lastly, note that if any entry is blank (written "--") then that particular property is simply not set for that particular item. Note that Inform reads articles such as "the" or "a" in the first column just as it would when something is created with any other sentence. It's even possible to define kinds this way, though it's rare to need to create many kinds at once. (See the worked example "Reliques of Tolti-Aph" at the Inform website. There's no special syntax needed: rather than saying "Some jerseys are defined by..." we would say "Some kinds of jersey are defined by...") Example 271 (**): Sweeney A conversation where each topic may have multiple questions and answers associated with it, and where a given exchange can lead to new additions to the list. Example 272 (***): Introduction to Juggling Assortment of equipment defined with price and description, in a table. 15.17. Defining values with tables Just as we can define many similar things (or kinds) using a table, we can also define a whole run of new values. Again, this avoids unnatural prose like The chemical elements are Hydrogen, Helium, Lithium, ..., and Ununquadium. But a further advantage is that by using a table we are able to give properties to values for the first time. For example: Solar distance is a kind of value. 1000 AU specifies a solar distance. Planet is a kind of value. The planets are defined by the Table of Outer Planets. Table of Outer Planets planet semimajor axis Jupiter 5 AU Saturn 10 AU Uranus 19 AU Neptune 30 AU Pluto 40 AU creates five values of the kind "planet", but it also makes a property called "semimajor axis" which belongs only to these five values. Thus: say "Pluto orbits at [semimajor axis of Pluto]." produces "Pluto orbits at 40 AU." We can both use and change this value: Praying is an action applying to nothing. Understand "pray" as praying. Instead of praying: now the semimajor axis of Pluto is 1 AU; say "Your prayers are answered, and the Almighty moves Pluto in closer to the fire." Similar properties would be made for each column of the table after the first (there can be any number of properties, including none). Because the values are created first, before the rest of the table is gone through, we can even use "planet" as one of the values of properties: Table of Outer Planets planet semimajor axis centre of government Jupiter 5 AU Jupiter Saturn 10 AU Saturn Uranus 19 AU Saturn Neptune 30 AU Pluto Pluto 40 AU Pluto All of this is intended to be closely parallel to defining a whole run of things, such as the coloured jerseys, using a table, but there are two important restrictions: firstly, when a kind of value is defined by table, the table must contain all of its possible values; and secondly, the column names (after the first) cannot coincide with names of any properties held by any other value (or thing, for that matter). So it is a good idea to give the columns very specific names ("centre of government") rather than vague names which might cause clashes elsewhere ("owner"). Two technical footnotes. In a table used to define a kind of value, blank entries are not left blank: they are filled in with suitable default values. For instance, if the semimajor axis column had been all "--"s except for listing Neptune at "30 AU", say, Inform would deduce that the column was meant to hold a value of kind "solar distance", and would set the solar distances for all of the other planets to be "0 AU". It does this to ensure that "solar distance of P" exists for any planet P. The second technical note is that we must not sort such a table, because it is used during play to store the properties, and if it were to get rearranged then so would the properties be - with probably disastrous results. 15.18. Table continuations A table is an arrangement for putting information together concisely in a single place, so it might seem odd that we sometimes need to divide it up: but once in a while, we do. Suppose we have: Table of Outer Planets planet semimajor axis Jupiter 5 AU Saturn 10 AU Uranus 19 AU Neptune 30 AU Pluto 40 AU But then someone in Chile with a telescope the size of God's own teacup notices something a long, long way out, and the newspapers get terribly excited. We can write an addendum: Table of Outer Planets (continued) planet semimajor axis Orcus 40 AU Quaoar 42 AU Xena 68 AU Sedna 502 AU This may seem unnecessary - why not simply add extra rows to the original table? - but it allows us to split the table between different parts of the source text, if we want to, or to continue a table which exists only in an extension. (Thus if we were using an extension which involved the planets, and had a table like this one, we would be able to add new planets without changing the extension.) The name for the continuation must be identical to the original. The continuation has no existence in its own right: Inform simply splices the two (or more) pieces together, exactly as if the table were all in one piece at the place where it first occurred. Thus the above creates only one table, the "Table of Outer Planets", with nine rows. Each column in the continuation must exist in the original, but not every column need be given: those omitted are filled with blank entries. The columns need not be in the same order. Both original and continuations are allowed to quote a number of blank rows: if so, the combined total is used. At time of writing the International Astronomical Union has not yet consented to name 2003 UB313 after Xena, the Warrior Princess, but this is surely only a bureaucratic delay. (Footnote: on 24 August 2006 it was demoted to dwarf planet status, though larger than Pluto, and on 13 September renamed Eris. Oh well.) Example 273 (*): Food Network Interactive Using a menu system from an extension, but adding our own material to it for this game. 15.19. Table amendments Tables can have amendments as well as continuations. The arrangement is much the same: a supplementary table supplies new rows for the original table. But instead of adding the new rows at the end of the original, as a continuation would, an amendment replaces matching rows in the original. (So the original stays the same size.) The amendment table must have exactly the columns of the original and in the same order. Moreover, each row in the amended table must match exactly one row in the original. For instance: Table of Plans moment outcome 10 AM "takeover of Mars" 11:30 AM "canals reflooded" 11:45 AM "chocolate bar production doubled" Table of Plans (amended) moment outcome 11:45 AM "volcanic cave production doubled" creates a three-row Table of Plans, with reference to the chocolate bars struck out. Amendment rows may be given in any order. The process of matching a row begins at the left-most column: Inform tries to see if any single row in the original table has a matching entry. If none does, a Problem is issued. If more than one do, Inform then looks at the second column, and so on. For instance: Enthusiasm is a kind of value. The enthusiasms are pumped, wired and languid. Table of Mental States feeling extent consequence pumped 1 "you feel able to run for your life" pumped 2 "you feel able to run for President" wired 1 "you feel able to run" languid 1 "you feel" Table of Mental States (amended) feeling extent consequence pumped 2 "you feel able to run for the Nebraska State Legislature" Here the amendment is made to the second row of the original table. The value in the leftmost column, "pumped", matches two rows in the original, so Inform moves on to the next column, reads "2", and finds that only one row in the original still qualifies - so that is the one replaced. For the present, at least, the columns used for matching may only contain: numbers, times, objects, action names, activities, figure names, sound names, truth states and any new kinds of value or units which have been declared. Example 274 (**): Trieste Table amendment to adjust HELP commands provided for the player. Chapter 16: Understanding 16.1. Understand During play, the computer and the player alternate in writing messages to each other: in the player's case, these are short instructions, usually saying what to do next. A wide range of such "commands" are automatically understood, but these only apply to the standard built-in actions. (This wide range is conveniently tabulated at the foot of the Actions index.) If we want the player to be able to command new actions, then we need to specify what is to be understood as what. For this, we supply special sentences starting with the word "Understand". Suppose we return to the earlier example of a newly created action: Photographing is an action applying to one visible thing and requiring light. We then supply lines of grammar (as they are called) for Inform to recognise, like so: Understand "photograph [someone]" as photographing. Understand "photograph [an open door]" as photographing. As usual, the square brackets indicate something which stands for text, rather than text to be taken verbatim. "[someone]" needs to be the name of anything of the kind "person", for instance (though as usual that person will need to be in sight of the player for the name to be accepted). The first word - in these examples "photograph" - must be something definite, not a substitution like this. For obvious reasons, this pattern of words needs to match the expectations of the action. Photographing applies to "one visible thing" - the "visible" just means it does not need to be touched, only seen - so neither of these would be allowable: Understand "photograph" as photographing. Understand "photograph [someone] standing next to [something]" as photographing. The first is bad because it supplies no things at all, the second because it supplies two: what we want, of course, is just the one. Example 275 (*): XYZZY Basics of adding a new command reviewed, for the case of the simple magic word XYZZY. Example 276 (*): Indirection Renaming the directions of the compass so that "white" corresponds to north, "red" to east, "yellow" to south, and "black" to west. Example 277 (**): Xylan Creating a new command that does require an object to be named; and some comments about the choice of vocabulary, in general. 16.2. New commands for old grammar In the photography example, we are providing entirely new grammar for an action not ordinarily built in to Inform. But we often want simply to provide alternative grammar for existing actions, or even to put new interpretations on commands that Inform already recognises. For instance: Understand "deposit [something] in [an open container]" as inserting it into. The inserting action is built in to Inform, but the command "deposit" is not, so this is created as new. It is occasionally useful to put a twist on this: Understand "fill [an open container] with [something]" as inserting it into (with nouns reversed). The clause "(with nouns reversed)" tells Inform to exchange the two nouns parsed, which is necessary because the inserting action expects the noun to be the item and the second noun to be the container, not vice versa. The following example: Understand "access [something]" as opening. might look as if it makes "access" behave just like "open" when the player types it, but that's not so: "open" can also be used in constructions like "open the door with the brass key", in which case it is understood as the unlocking action. We could add another line to make "access" behave this way too, but if what we really want is to make "access" behave just like "open", it's easier simply to say so: Understand the command "access" as "open". This is very useful when adding a new command which needs synonyms: Understand the commands "snap" and "picture" as "photograph". We can check the current stock of commands by looking at the table in the Actions index: for instance, before making "snap" synonymous with "photograph", it might be wise to check that it is not already defined as a command for breaking something. Example 278 (*): Anchorite By default, Inform understands GET OFF, GET UP, or GET OUT when the player is sitting or standing on an enterable object. We might also want to add GET DOWN and DOWN as exit commands, though: Example 279 (*): Alpaca Farm A generic USE action which behaves sensibly with a range of different objects. Example 280 (****): Cloak of Darkness Implementation of "Cloak of Darkness", a simple example game that for years has been used to demonstrate the features of IF languages. 16.3. Overriding existing commands Suppose we are devising specialist commands for a game of whist, and we want "discard" as one of them. Looking at the table of commands in the Action index, we find that, inconveniently enough, "discard" already has a meaning: it is synonymous with "drop", and while that might be sensible most of the time, it is perfectly wrong now. We need a way to free up "discard" for our own use. We can do that by: Understand the command "discard" as something new. This cuts it loose, so to speak, and ready to be given new meanings. If we check the Actions index again, we find no mention of "discard" - it is now a blank slate - but "drop" is still exactly as it was. We could now say something like: Understand "discard [something]" as discarding. (If we had declared that "drop" was something new, the whole thing would have happened in reverse, with "discard" retaining all of the original grammar. Inform does not distinguish between a command and its synonym.) The "... as something new" sentence works even for a command which did not exist anyway, for instance with: Understand the command "zylqix" as something new. Of course this does nothing - but it is intentional that it generates no problem messages: it means that the sentence can be used to force a command to be fresh and untouched by previous definitions, which might be useful when working with extensions by other people. Example 281 (*): The Trouble with Printing Making a READ command, distinct from EXAMINE, for legible objects. Example 282 (**): Lanista 2 Randomized combat in which the damage done depends on what weapons the characters are wielding, and in which an ATTACK IT WITH action is created to replace regular attacking. Also folds a new DIAGNOSE command into the system. 16.4. Standard tokens of grammar We have already seen "[something]" and "[someone]", which are standard examples of "tokens of grammar" - patterns matched by suitable named things. There are several other standard tokens, provided not so much from necessity but to allow the game parser to be more graceful and responsive. "[someone]" matches the same possibilities as "[a person]" would, but the parser handles it a little better in cases of failure. These special tokens are best explained by looking at some of the examples in the standard grammar, which can be browsed in the Index of any game. Understand "wear [something preferably held]" as wearing. Here we expect that the named item will be one that is held by the player, and the parser will use this to resolve ambiguities between names of things carried and not carried. (If the action is one which positively requires that its noun be something carried, such as "eating", then a command matching this token against something not carried will generate an automatic attempt to take it.) Understand "take [things]" as taking. Understand "drop [things preferably held]" as dropping. "[things]" is like "[something]" but allows a list of items, or a vague plural like "all", to be typed. The result will be a sequence of actions, one for each item thus described. "[things preferably held]" is the analogous token for "[something preferably held]". Understand "take [things inside] from [something]" as removing. "[things inside]" matches only what is inside the second-named thing, and ensures that (for instance) the command "take all from box" does not also try to take the box. Understand "put [other things] in/inside/into [something]" as inserting it into. Similarly, "[other things]" will allow anything except the second-named thing. (Like "[things inside]" it is really only needed for handling containers.) Example 283 (*): Shawn's Bad Day Allowing the player to EXAMINE ALL. Example 284 (***): The Left Hand of Autumn The possibility of using a [things] token opens up some interesting complications, because we may want actions on multiple items to be reported differently from actions on just one. Here we look at how to make a multiple examination command that describes groups in special ways. 16.5. The text token Most actions involve items: taking a vase, perhaps. As we shall see, they might also involve values, or a mixture of the two: turning a dial to 17 would involve both a thing (the dial) and a number (17). A few of Inform's built-in actions, however, can act on any text at all. For instance, asking the Sybil about the Persian army would involve a thing (the Sybil) and some text ("Persian army"). Inform does not try to understand automatically what that text might mean, or to relate it to any items, places or values it knows about: instead, Inform leaves that to the specific story to work out for itself, since the answer is bound to depend on the context. (In the chapter on Tables, we saw ways to compile tables of responses to particular topics of conversation.) The token for "accept any text here" is just "[text]". For instance, if we create an action with: Getting help about is an action applying to one topic. We can then provide grammar for this action like so: Understand "help on [text]" as getting help about. When text like this is successfully matched, it is placed in a value called "the topic understood". (The term "topic" is used traditionally, really: most of the times one needs this feature, it's for a topic of conversation, or a topic being looked up in a book.) Example 285 (*): Ish. A (very) simple HELP command, using tokens to accept and interpret the player's text whatever it might be. Example 286 (**): Nameless ASKing someone about an object rather than about a topic. 16.6. Actions applying to kinds of value Almost all actions apply to things: the player picks them up, pushes them, looks at them and so on. We only occasionally need to recognise other kinds of value, but when we do, we can. For instance: Adjusting it to is an action applying to one thing and one number. Understand "adjust [something] to [a number]" as adjusting it to. The substitution "[a number]" matches any number (actually any whole number that is not too large) typed by the player. Inform checks the various kinds being used to make sure that everything matches, so, for instance, this would be disallowed: Understand "adjust [something] to [something]" as adjusting it to. Example 287 (*): Safety A safe whose dial can be turned with SPIN SAFE TO 1131, and which will open only with the correct combination. Example 288 (*): Tom's Midnight Garden A clock kind that can be set to any time using "the time understood"; may be turned on and off; and will advance itself only when running. Time on the face is also reported differently depending on whether the clock is analog or digital. Example 289 (**): Ibid. A system which allows the author to assign footnotes to descriptions, and permits the player to retrieve them again by number, using "the number understood". Footnotes will automatically number themselves, according to the order in which the player discovers them. 16.7. Understanding any, understanding rooms Ordinarily, if we write Understand "manipulate [something]". then the "[something]" will only match what is within reach or sight: this is the concept of "scope", which is what prevents a player from spookily acting on objects from a distance. The parser itself prevents the manipulation rules from ever being invoked on such distant items, which is as it should be. Sometimes, though, we positively want to allow this possibility. If we use the special word "any", as in Understand "manipulate [any door]". then any door, anywhere in the model world, can be allowed in the player's command. (Of course, the manipulation rules may not do what the player hopes: all that has happened is that the command is now possible to type.) The "any" can be followed by any description of items or rooms, and the latter opens up new possibilities, since rooms are ordinarily never allowed to be named in the player's commands. For example, the following gives the player the ability to walk between rooms without giving explicit directions of movement. Going by name is an action applying to one thing. Carry out going by name: say "You walk to [the noun]."; move the player to the noun. Understand "go to [any adjacent visited room]" as going by name. (This is really only a sketch: in a finished work, "go to" would produce helpful errors if non-adjacent but visited rooms were named, and we might also worry about rules applying to movement, because the method above will circumvent them.) Example 290 (*): One of Those Mornings A FIND command that allows the player to find a lost object anywhere Example 291 (**): Actaeon A FOLLOW command allowing the player to pursue a person who has just left the room. 16.8. Understanding names So far in this chapter, Understand sentences have been used to give names to actions, but they can also be used to name objects - in particular, things and rooms. This normally happens automatically. For instance, writing The St Bernard is an animal in the Monastery Cages. makes ST BERNARD refer to the dog, and MONASTERY CAGES refer to the room. But sometimes, as here, that isn't really enough. Why shouldn't the player type EXAMINE DOG? One way to allow this is to write: Understand "dog" as the St Bernard. Matters become more complicated when the player wants to refer to more than one object at once. When a kind is created, and the source text constructs multiple duplicate items of that kind, Inform generates a plural of the kind's name in order to understand commands referring to these multiples. For instance, given... The Lake is a room. A duck is a kind of animal. Four ducks are in the Lake. ...the player can type TAKE DUCKS to try to pick up all four. Once again the automatic behaviour can be enhanced: Understand "birds" and "ruddy ducks" as the plural of duck. Now TAKE BIRDS and TAKE DUCKS are equivalent. Plurals can even, strange as it may seem, be given for single things: The magpie is in the Lake. Understand "birds" as the plural of the magpie. And now TAKE BIRDS tries to take all four ducks and the magpie too. 16.9. Understanding kinds of value In many cases, if K is the name of a kind of value, then Inform automatically makes an Understand token called "[K]" which matches only values of K. An example is "[number]", which matches text like 203 or SEVEN. There is a chart of the kinds of value in the Kinds index for a project, showing which ones can be understood in this way. In particular, any newly created kind of value can always be understood. We make good use of that in the example game "Studious": "Studious" The Studio is a room. "The unreal world of the photographic studio, full of fake furniture, cantilevered stands and silver-white shades like miniature parachutes." The lumpy black camera is in the Studio. "A lumpy black camera hangs from a tripod." The rake-thin model is a woman in the Studio. "A rake-thin model, exquisitely bored and boringly exquisite, angles herself indolently." Limb is a kind of value. The limbs are left leg, left arm, right leg and right arm. Detailing is an action applying to one limb and one visible thing, requiring light. Check detailing: if the camera is not carried then say "You can hardly photograph without a camera, now can you?" instead. Report detailing: say "Click! You take a detail photograph of the [limb understood] of [the second noun]." Understand "photograph [limb] of [a person]" as detailing. Test me with "get camera / photograph left leg of model". Note the way we can refer to the limb mentioned by the player as the "limb understood". Similarly, we could talk about the "number understood" if the value parsed had been a number, and so on. One of the built-in kinds of value is worth special note: time. A time can hold either a specific time of day, such as 10:23 PM, or a duration of something, such as 21 minutes. The "[a time]" token matches times of day, such as 10:15 AM or MIDNIGHT. But 10 MINUTES wouldn't be recognised by "[a time]" since it isn't a specific moment in the day. To get around this, an alternative version called "[a time period]" is available. So: Understand "wait for [a time period]" as ... would match WAIT FOR AN HOUR or WAIT FOR TWO HOURS 12 MINUTES. Example 292 (*): Pages A book with pages that can be read by number (as in "read page 3 in...") and which accepts relative page references as well (such as "read the last page of...", "read the next page", and so on). Example 293 (**): Down in Oodville Offering the player a choice of numbered options at certain times, without otherwise interfering with his ability to give regular commands. Example 294 (***): Straw Into Gold Creating a Rumpelstiltskin character who is always referred to as "dwarf", "guy", "dude", or "man" -- depending on which the player last used -- until the first time the player refers to him as "Rumpelstiltskin". 16.10. Commands consisting only of nouns In every example so far, and in almost all practical cases, the first word in a command which results in an action will be something fixed: a verb, in fact. When we write Understand "photograph [something]" as photographing. we are saying that the first word of such a command will always be "photograph". Occasionally, though, we would like to understand a noun as a command, perhaps in a situation where the command is obvious. If we say: Understand "[something]" as examining. then the command "examine" will be implicit when the player types a bare noun: A red box and a blue ball are here. > BALL The blue ball is plaited from many small leather patches. so that the command "ball" has resulted in the action "examining the blue ball". This is a feature which should be used sparingly, since it could easily lead to confusion if not carefully explained to the player. By default, it is not used at all. It also has what may be a serious limitation: verbless commands like this work only when typed by the player as actions to follow - they do not work as instructions for other people. So for instance SVEN, BALL would not ask Sven to try examining the ball - instead it would generate the action "answering ball to Sven". (This is because the Inform parser decides whether PERSON, SOME TEXT is a request or just conversation by looking at the first word after the comma to see if it's a command.) Example 295 (*): Misadventure A going by name command which does respect movement rules, and accepts names of rooms as commands. Example 296 (**): Safari Guide The same functionality, but making the player continue to move until he reaches his destination or a barrier, handling all openable doors on the way. 16.11. Understanding values So far every "Understand" sentence has ended with "as" and a description of an action. But we can also use "Understand" to supply new ways to talk about things and even values. For instance, if we create: A brass lantern is in the Building. then it can be called "brass", or "lantern", but not "lamp": Inform does not really know what these words mean, and has no grasp of synonyms. We can arrange for "lamp" to work as well like so: Understand "lamp" as the lantern. Understand "old lamp" as the lantern. With care, we can do the same trick for entire kinds of thing at once. It is not ordinarily the case that a thing can be called by the name of its kind: if we put a woman called April into a room, then she can usually be called "April", but not "woman". (The exception is when we do not specify any name for her - in that case, Inform will give up and call her just "woman".) So there is not usually any form of words which can refer to anything of a given kind. If we should want this, we have to say so explicitly: Understand "machine" as a device. Device is a kind, so now the word "machine" can be used to refer to any device: if there are two in the same place, the result might play out like so: >switch machine on Which do you mean, the bale twiner or the grain thresher? >twiner You watch absorbed as a perfect cube of hay is trussed up like a parcel. Similarly, we might conceivably want to allow new ways to recognise values - in this case, a number: Understand "eleventy-one" as 111. When making complicated names, we need to watch out for the possibility of writing a definition which will cause Inform to go around in circles (something which will show up as a "Too many activities at once" run-time problem). For instance, Understand "[thing] substitute" as the placebo. will fail because Inform, working left to right, needs to look for every possible object name before it can progress: one possibility is the placebo itself: to check that, it needs to look for every possible object name: and so on, never finishing. A definition like this one very likely matches too much in any case (would we really want to accept PLACEBO SUBSTITUTE or CIGARETTE SUBSTITUTE SUBSTITUTE SUBSTITUTE here, as the definition implies?). Example 297 (*): Palette An artist's workshop in which the canvas can be painted in any colour, and where painterly names for pigments ("cerulean") are accepted alongside everyday ones ("blue"). Example 298 (***): Baritone, Bass Letting the player pick a gender (or perhaps other characteristics) before starting play. 16.12. This/that We have already seen "or" used in "Understand" sentences: Understand "scarlet" or "crimson" as red. In general, any number of alternative forms can be given which are to be understood as the same thing (in this case the colour red). When the alternatives are in any way complicated, "or" should always be used, but a shorthand form is allowed for simple cases where it is only a matter of a single word having several possibilities: Understand "reach underneath/under/beneath [something]" as looking under. This is shorthand for: Understand "reach underneath [something]" or "reach under [something]" or "reach beneath [something]" as looking under. Which in turn is shorthand for: Understand "reach underneath [something]" as looking under. Understand "reach under [something]" as looking under. Understand "reach beneath [something]" as looking under. To recapitulate: the slash "/" can only be used between single, literal words, and is best for the wayward prepositions of English ("in/into/inside", and so forth). For anything more complex, always use "or". 16.13. New tokens We have now made good use of square-bracketed tokens, such as "[something]", in a variety of "Understand..." sentences. It is sometimes convenient to create new tokens of our own, to match whatever grammar we choose: this enables complicated knots of grammar to be used in many different "Understand..." sentences without having to write it all out each time. For instance, here are new tokens: one for each of two groups of alternative prepositions. Understand "beneath/under/by/near/beside/alongside/against" or "next to" or "in front of" as "[beside]". Understand "on/in/inside" or "on top of" as "[within]". Again, note that the slash indicates a choice between words only, not between entire phrases. For instance, Understand "red bird/robin" as "[robin]". breaks down to understanding either "red bird" or "red robin", not "red bird" or "robin". By contrast, Understand "red bird" or "robin" as "[robin]". will understand either "red bird" or "robin" but not "red robin". If we want to capture all three forms, we might define Understand "red bird/robin" or "robin" as "[robin]". Example 299 (*): Lies Commands to allow the player to lie down in three different ways. 16.14. Tokens can produce values The examples just seen were tokens which simply matched specific words typed by the player, but newly created tokens can also produce values: Colour is a kind of value. The colours are red, green and blue. Understand "colour [a colour]" or "[a colour] shade" as "[tint]". Here the "[tint]" token matches, for instance, "colour red" and "blue shade", which would result in the values red and blue, respectively. Tokens are not allowed to produce more than one value, and if several patterns are given to define them then those patterns have to be compatible. That means the following is disallowed, since it might work out to a colour, or to an object, leaving Inform unable to judge whether an action can safely be applied to the result. Understand "colour [a colour]" or "[something]" as "[tint]". 16.15. Understanding things by their properties Items are ordinarily understood only by their original given names. For instance, if we have: In the Herb Garden is a china pot. then the player could refer to this as "pot", "china pot" or "china". We can embellish this by adding extra forms: Understand "chinese pot" or "chinese vase" as the china pot. But suppose the pot changes its nature in the course of play? If we have: The china pot can be unbroken or broken. The china pot is unbroken. After dropping the china pot: say "Crack!"; now the china pot is broken; now the printed name of the pot is "broken pot". So now the player would reasonably expect to call it "broken pot", a wording which would have been rejected before. We can achieve this by writing: Understand the unbroken property as describing the pot. which allows "unbroken" or "broken" to describe the pot, depending on its state. And, since the player might well use a different adjective but with the same idea in mind, we can even add: Understand "shattered" or "cracked" or "smashed" as broken. Understand "pristine" as unbroken. This is something of a toy example, but the feature looks rather more useful when there are more pots than just one: "Terracotta" A flowerpot is a kind of thing. A flowerpot can be unbroken or broken. Understand the broken property as describing a flowerpot. After dropping an unbroken flowerpot: say "Crack!"; now the noun is broken; now the printed name of the noun is "broken flowerpot"; now the printed plural name of the noun is "broken flowerpots". The Herb Garden is a room. In the Herb Garden are ten unbroken flowerpots. We then have the dialogue: Herb Garden You can see ten flowerpots here. >get two flowerpots flowerpot: Taken. flowerpot: Taken. >drop all flowerpot: Crack! flowerpot: Crack! >look Herb Garden You can see two broken flowerpots and eight flowerpots here. >get an unbroken flowerpot Taken. and so on and so forth. There are in fact two slightly different forms of this kind of sentence: Understand the broken property as describing a flowerpot. Understand the broken property as referring to a flowerpot. The only difference is that in the "describing" case, the property's name alone can mean the thing in question - so "take unbroken" will work; whereas, in the "referring to", the property's name can only be used as an adjective preceding the name of thing itself - so "take unbroken flowerpot" will work but "take unbroken" will not. Example 300 (*): Aspect Understanding aspect ratios (a unit) in the names of televisions. Example 301 (*): Hymenaeus Understanding "flaming torch" and "extinguished torch" to refer to torches when lit and unlit. Example 302 (**): Terracottissima The flowerpots once again, but this time arranged so that after the first breakage all undamaged pots are said to be "unbroken", to distinguish them from the others. Example 303 (**): Peers The peers of the English realm come in six flavours - Baron, Viscount, Earl, Marquess, Duke and Prince - and must always be addressed properly. While a peerage is for life, it may at the royal pleasure be promoted. Example 304 (**): Channel 1 Understanding channels (a number) in the names of televisions. Example 305 (***): Terracottissima Maxima Flowerpots with textual names that might change during play. Example 306 (***): Tilt 1 A deck of cards with fully implemented individual cards, which can be separately drawn and discarded, and referred to by name. Example 307 (***): Channel 2 Understanding channels (a number) in the names of televisions, with more sophisticated parsing of the change channel action. 16.16. Understanding things by their relations Sometimes it makes sense for the name of something to involve the names of other things to which it is related. For instance, if we say TAKE THE BOTTLE OF WINE, we mean that the bottle currently contains wine - if it were the very same bottle containing water, we would call it something else. For names which must involve related names, a special form of token is provided. For instance, we could say: A box is a kind of container. Understand "box of [something related by containment]" as a box. The Toyshop is a room. The red box is a box in the Toyshop. Some crayons are in the red box. and now TAKE BOX OF CRAYONS will work, because CRAYONS matches against "[something related by containment]" for the red box - or it does for as long as the crayons are there. We can have similar matches against relations of all kinds, but have to name the relation explicitly, using its one-word name. (See the examples at the end of this section for plenty of cases.) We can also reverse the sense. If we write: A box is a kind of container. Understand "box in [something related by reversed containment]" as a box. The Toyshop is a room. The crate and the hammock are in the Toyshop. In the crate is a box. In the hammock is a box. then TAKE THE BOX IN THE HAMMOCK will work: here, the relation goes the other way, because the box is being contained by the other-named item, rather than doing the containing. Example 308 (*): Puncak Jaya When a character is not visible, responding to such commands as EXAMINE PETER and PETER, HELLO with a short note that the person in question is no longer visible. Example 309 (*): Whither? A door whose description says where it leads; and which automatically understands references such as "the west door" and "the east door" depending on which direction it leads from the location. Example 310 (*): Cinco A taco shell that can be referred to (when it contains things) in terms of its contents. Example 311 (**): Claims Adjustment An instant camera that spits out photographs of anything the player chooses to take a picture of. 16.17. Context: understanding when We have now seen several different forms of "Understand" sentence: for instance, Understand the colour property as describing a building block. Understand "mix [colour] paint" as mixing paint. Understand "rouge" as red. Understand "curious girl" as Alice. Any of these may optionally have a condition tacked on: for instance, Understand "mix [colour] paint" as mixing paint when the location is the Workshop. Understand "rouge" as red when the make-up set is visible. In principle, "when ..." can take in any condition at all. In practice a little care should be exercised not to do anything too slow, or which might have side-effects. (For instance, referring the decision to a phrase which then printed text up would be a bad idea.) Moreover, we must remember that the "noun" and "second noun" are not known yet, nor do we know what the action will be. So we cannot safely say "when the noun is the fir cone", for instance, or refer to things like "the number understood". (We aren't done understanding yet.) If we want more sophisticated handling of such cases, we need to write checking rules and so on in the usual way. Contexts can be useful to make sense of things having different names depending on who is being spoken to, as here: Understand "your" as a thing when the item described is held by the person asked. With this rule in place FRODO, GIVE ME YOUR RING means that Frodo will know which ring is meant, even if there are a couple of dozen other rings present. If the name of something has to change completely, perhaps because the player's understanding of events has changed completely, then Inform's standard way of handling names can be a nuisance. When an item or room is created, Inform automatically makes its name understood as referring to it (in fact, it makes each individual word in that name understood). For instance, The Wabe is a room. The blue peacock and the sundial are in the Wabe. means that the player can type EXAMINE BLUE PEACOCK or PUSH SUNDIAL or SHOWME WABE or TAKE BLUE, and so on. This is almost always a good thing, and here there's no problem, because peacocks and sundials are not usually disguised. But here is a case where a disguise is needed: The secret document is a privately-named thing in the drawer. The printed name of the secret document is "[if the secret document is handled]secret document[otherwise]dusty paper". Understand "dusty" and "paper" as the secret document. Understand "secret" and "document" as the secret document when the secret document is handled. After taking the secret document for the first time: say "Heavens! It is the secret document!" As this demonstrates, the either/or property "privately-named" makes Inform create a thing or room which starts out with no automatic understandings at all. The name it happens to have in the source text is ignored. If we simply write: The ungraspable concept is a privately-named thing in the Dining Room. then nothing the player can type will ever refer to it; though he will see it, and even be able to pick it up by typing TAKE ALL. The reverse property is "publically-named", which all things and rooms are by default. (Privately-named is a property which only affects how Inform creates the object, and it can't usefully be given or taken away during play. "Understand ... when ..." is the way to change names during play.) Example 312 (*): Quiz Show In this example by Mike Tarbert, the player can occasionally be quizzed on random data from a table; the potential answers will only be understood if a question has just been asked. Example 313 (**): Bibliophilia A bookshelf with a number of books, where the player's command to examine something will be interpreted as an attempt to look up titles if the bookshelf is present, but otherwise given the usual response. 16.18. Changing the meaning of pronouns The pronouns IT, HIM, HER and THEM are constantly adjusted during play, to save the player time when typing commands. If the player types EXAMINE NECKLACE on one turn, it's sufficient to type TAKE IT on the next, and IT will be understood as meaning whatever NECKLACE meant last turn. All of that happens automatically, but once in a while the result can be unfortunate. Suppose that when the player examines the necklace, a security system automatically drugs her unconscious, and she wakes up in a cell, hours later, and is told that the cell is bare except for a key on the floor. If she types TAKE IT, she clearly doesn't mean IT to mean the necklace any more; she means the key. Inform's parser can't make guesses like this, so the following phrase can be used to help it.

set pronouns from (object)
This phrase adjusts the meaning of pronouns like IT, HIM, HER and THEM in the command parser as if the object mentioned has become the subject of conversation. Example: the combination of set pronouns from the key; set pronouns from Bunny; might change IT to mean the silver key and HIM to mean Harry "Bunny" Manders, while leaving HER and THEM unaltered.
(Beta release note) Previous builds of Inform also allowed:

set pronouns from possessions of the player
This phrase is now deprecated. It has the same effect as: repeat with item running through things held by the player: set pronouns from the item. and is being withdrawn as unnecessary and very rarely needed.
Example 314 (*): Pot of Petunias Responding sensibly to a pot of petunias falling from the sky. 16.19. Does the player mean... When the player types an ambiguous reference, we need to work out what is meant. Consider the following source text: The Champs du Mars is a room. The great Eiffel Tower is here. "The great Tower stands high over you." The souvenir model Eiffel Tower is here. "Comparatively tiny is the souvenir version." Now suppose the player types GET TOWER. The response will be: Which do you mean, the great Eiffel Tower or the souvenir model Eiffel Tower? Which is a silly question, exposing our work of IF as something artificial. It's obvious to the author of the source text, and to the player, that the souvenir must be what is meant: but this is not obvious to the computer program running the game. Works of IF gain a subtle feeling of quality from being able to understand ambiguous references of the kind above, and Inform provides us with a way to do this by giving the parser clues in the form of "Does the player mean..." rules. For instance, if we add: Does the player mean taking the great Eiffel Tower: it is very unlikely. then the response to GET TOWER will now be: (the souvenir model Eiffel Tower) Taken. "Does the player mean..." rules look at the actions which are possible interpretations of what the player typed, and grade them according to how likely they seem. (Note that these rules are only ever used to handle ambiguities: if the player unambiguously types GET GREAT EIFFEL TOWER, that will be the action. And the rules are only used where they are able to make a decision: if there are still multiple equally plausible meanings, the parser will ask about all possibilities, not just the most likely ones.) Rules in this rulebook can either decide nothing, or come up with one of the following verdicts: it is very likely it is likely it is possible it is unlikely it is very unlikely If there are no "does the player mean" rules, or the rules make no decision on a given possible action, it will be ranked as "it is possible". We may use these rules to affect all sorts of interaction with a specific object or kind of object, as in Does the player mean doing something with the cursed dagger of Thog: it is very unlikely. Does the player mean doing something with the cursed dagger of Thog when the player is hypnotized: it is likely. ...and so on. Notice that we can also make rules about actions that apply to two objects, so for instance: Does the player mean throwing the can of shoe polish at the shoe polish vending machine: it is likely. which nicely clarifies THROW POLISH AT POLISH, but does not comment on the likelihood of throwing the can at other things or of throwing other things at the vending machine. Moreover, the (suspected) identity of the first item will be known when the rule is consulted; thus Does the player mean tying the noun to the noun: it is very unlikely. will tell Inform to prefer not to tie something to itself if other interpretations are available. But there is a caveat. There are some cases where this mechanism will not in fact help Inform to choose its way out of an ambiguous command, because of the way it parses one noun at a time. It usually needs to understand the first noun before it will even try to make sense of the second. So a rule like: Does the player mean throwing the can of shoe polish at the tree: it is likely. may not work if the player types THROW POLISH AT TREE and POLISH is ambiguous, because when the parser is trying to understand POLISH, it hasn't yet seen to the end of the command and realised that the second noun will be the tree; so the second noun is unset and the rule won't match. As a caveat to the caveat, the "inserting it into", "removing it from" and "putting it on" actions have this slightly back to front. These are parsed using the (little-used) "[other things]" or "[things inside]" tokens, and the Inform parser tries to detect the second noun before the first one, since the identity of the first has to depend on the second. So for instance if the situation contains "an oak tree" and also "an oak chest", we could write: Does the player mean inserting into the oak chest: it is very likely. which would successfully make PUT COIN IN OAK mean the chest, not the tree. (Note the way we write "inserting into" without saying anything about what's being inserted, not even that it's "something".) Example 315 (*): Masochism Deli Multiple potatoes, with rules to make the player drop the hot potato first and pick it up last. 16.20. Understanding mistakes When inspiration strikes the player, he can usually be relied upon to make a good-faith effort to communicate the new idea: he will guess the right command. If he guesses wrongly, the mistake is probably the author's, because a good author will try to anticipate all possible wordings and make all of them work. Nevertheless it is sometimes good practice to nudge the player towards the right wording - particularly if the player has the right idea but is not explicit enough: for instance, typing TALK TO JUDGE when we really want to know what is to be said (JUDGE, GUILTY); or if the player tries something like PLAY CHESS rather than MOVE PAWN TO KING 4. Similarly, if we make a casual reference such as "In your childhood days, you loved sliding in stocking feet across this hallway", a player might type SLIDE IN STOCKING FEET: a nice idea, and which deserves a nice response, even though it asks to do something beyond the scope of the game. Inform provides a simple mechanism for recognising a command but at the same time recognising that it does not properly specify an action. Such commands are called "mistakes", for the sake of a memorable term, but the player has not really behaved badly, and should be helped rather than reproved. For instance: Understand "act" as a mistake. While that works - the command to "act" is indeed rejected - it is not very good, because no very helpful message is brought up. The following is much better: Understand "act" as a mistake ("To join the actors, you have to adopt a role in the play! Try PLAY HAMLET or similar."). Or we could once again insist on a given context: Understand "act" as a mistake ("To join the actors, you have to adopt a role in the play! Try PLAY HAMLET or similar.") when the location is the Garden Theatre. That still has the drawback that the command "act hamlet" will not be recognised: so the final version we want is probably Understand "act [text]" as a mistake ("To join the actors, you have to adopt a role in the play! Try PLAY HAMLET or similar.") when the location is the Garden Theatre. since the "[text]" part will soak up any words the player types (or none), meaning that any command at all whose first word is "act" will be matched. We need to be careful to avoid circular things like this: Understand "[text]" as a mistake ("'[the topic understood]' is something I really wish you wouldn't say.") when the topic understood is a topic listed in table 1. This doesn't work because the topic understood isn't set until the line has been understood, but Inform checks the "when..." condition before it tries to understand the line. Indeed, even this: Understand "[text]" as a mistake ("'[the topic understood]' is something I really wish you wouldn't say."). is unsafe (quite apart from being unwise!) - again, "topic understood" doesn't exist for a mistake, because in a mistake, nothing is understood. The following is often useful during beta-testing of a new work, though we would not want it in the final published edition. Many authors like to ask their testers not to try anything in particular, simply to play naturally: but to record the transcript of the session, and email it back to the author. The following command is a device to allow the tester to type a comment in to the transcript: Understand "* [text]" as a mistake ("Noted."). For instance, the tester might type "* DIDN'T WE SAY DARCY WAS TALL?", to which the game would reply "Noted." - and the author can search for such comments when receiving the transcript. If we are careful, we can make the reply depend on what was typed in the mistaken command: Understand "steal [something]" as a mistake ("Just TAKE [the noun] and leave without paying: that's stealing in my book."). The care comes in because Inform applies much less checking to mistakes than to other actions, and odd errors will result if we try to refer to (say) "the second noun" in a command which did not have a second noun. It's probably wise to take particular care if using "as a mistake" with any command which might include the mistake among what the player calls ALL: for example, if "take [sydney harbour bridge]" is understood as a mistake, then TAKE ALL will may result in this, even though the player doesn't intend any such thing. Example 316 (*): Query Catching all questions that begin with WHO, WHAT, WHERE, and similar question words, and responding with the instruction to use commands, instead. Example 317 (*): The Gorge at George If the player tries to TALK TO a character, suggest alternative modes of conversation. Example 318 (***): Hot Glass Looks Like Cold Glass Responding to references to a property that the player isn't yet allowed to mention (or when not to use "understand as a mistake"). 16.21. Precedence When several different lines of grammar are supplied to meet the same circumstances, it makes a big difference what order they are tried in. For instance, suppose we have: Understand "photograph [a door]" as photographing. Understand "photograph [an open door]" as photographing. The second line is more specific than the first, so Inform takes these grammar lines the other way around: it checks for "open door" before it checks for "door". That didn't matter here, since both lines came out with the same result (the action of photographing), but it matters very much in the next example: Understand "employ [a door]" as opening. Understand "employ [an open door]" as entering. More subtle is a line already seen: Understand "on/in/inside" or "on top of" as "[within]". Here Inform puts "on top of" before "on/in/inside", since otherwise only the "on" of "on top of" will be recognised. Mistakes always take precedence over non-mistakes: this is intended to make sure that Understand "take umbrage" as a mistake ("Nobody takes umbrage in this game, mister."). will take precedence over Understand "take [something]" as taking. even if there is, in fact, a character called Mr Nimbus Umbrage so that the command could conceivably make sense. Example 319 (*): Some Assembly Required Building different styles of shirt from component sleeves and collars. Example 320 (***): Lakeside Living Similar to "Lemonade", but with bodies of liquid that can never be depleted, and some adjustments to the "fill" command so that it will automatically attempt to fill from a large liquid source if possible. 16.22. Review of Chapter 16: Understanding "Understand..." rules are used in Inform to change both how the player can give commands (such as POLISH THE SILVER) and how the player is allowed to refer to individual objects. 1. Understanding the names of things. As we've seen since the earliest chapters, we may add to the vocabulary used to refer to an object in the game, or to an entire class: Understand "fish" as the trout. Understand "fish" or "dinner" as the trout. Understand "fish/dinner" as the trout. Understand "gentleman" as a man. If we use an entire phrase, as here Understand "red bird" as the robin. Inform will match only the full phrase and not its components; so EXAMINE RED BIRD would work, but not EXAMINE RED or EXAMINE BIRD. If we have a combination of words we expect to use together very often, we can create a special understanding token, such as Understand "red" or "scarlet" or "vermilion" or "vermillion" or "cinnabar" as "[red]". Understand "red/scarlet/vermilion/vermillion/cinnabar" as "[red]". and then use this to define other understand rules, as in Understand "[red] bird" as the robin. 2. Understanding properties and conditional states. Often we want to allow the player to use adjectives or names for objects only at some points in the game or under some circumstances. Understand "Janine" as the stranger when the stranger is known. Understand the heat property as describing a pan. Understand the heat property as referring to a pan. Understand "lady" as a woman when the item described is ennobled. The distinction between referring and describing is that in the "describing" case, the property's name alone can mean the thing in question - so "take unbroken" will work; whereas, in the "referring to", the property's name can only be used as an adjective preceding the name of thing itself - so "take unbroken flowerpot" will work but "take unbroken" will not. We can also make use of relationships to other things. For instance, Understand "[something related by support] taco" as the taco. allows BEEF TACO to mean the taco when something which can be named BEEF is on top of (that is, supported by) the taco. If we want to conditionally add to the way the name of something is displayed (e.g., to put "broken" in front of the name of any damaged pot), we may want to use the "printing the name" and "printing the plural name" activities; see the Activities chapter for more details. 3. Understanding actions. We use understand sentences to tell Inform how a player is allowed to give a command. For clarity, these sample understand rules are listed together with the way the action might be defined: Understand "help" as asking for help. Asking for help is an action out of world. Understand "whistle" as whistling. Whistling is an action applying to nothing. Understand "shake [something]" as shaking. Shaking is an action applying to one thing. Understand "seduce [someone]" as seducing. Seducing is an action applying to one thing. Understand "spy on [any thing]" as spying on. Spying on is an action applying to one visible thing. Understand "go to [any room]" as going to by name. Going to by name is an action applying to one thing. Understand "mix [something] with [something]" as mixing it with. Mixing it with is an action applying to two things. Understand "fill [an open container] with [something]" as inserting it into (with nouns reversed). Inserting it into is an action applying to two things. Notice in this case that, since there are two objects affected by the action, our action name includes an "it" where the first of the two nouns would go. In a few special cases we might provide an understand rule that accepted unusually terse input: Understand "[something]" as examining. Understand "[any visited room]" as going to by name. We may also occasionally write understand rules that supply less information that the action needs to go forward (by offering too few nouns or values), when we intend to use the "supplying a missing noun" or "supplying a missing second noun" activities. So for instance: Stabbing it with is an action applying to two things. Understand "stab [something] with [something]" as stabbing it with. Understand "stab [something]" as stabbing it with. Rule for supplying a missing second noun when stabbing something with: now the second noun is the hypodermic needle. For more details, see the Activities chapter. 4. Action synonyms. We may create synonyms for existing commands with lines such as Understand the commands "mingle" and "combine" as "mix". and conversely we may tell Inform not to understand a command in the way it currently does with Understand the command "murder" as something new. Understanding a command as something new removes Inform's knowledge of all grammar applying to that specific word; so Understand the command "get" as something new. would not change Inform's understanding of TAKE FISH but would remove its understanding of GET FISH GET UP GET DOWN GET IN BOX GET ALL FROM BASKET and so on. While it might be nice to be able to cancel the understanding of single lines of grammar while leaving all other senses of "get" intact, there is currently no facility for doing this. It is not effective to write a line such as Understand the command "get [something]" as something new. 5. Value tokens. Understand rules for actions may also use tokens to accept kinds of value, numbers, or strings of text of any length: Understand "discuss [text]" as discussing. Discussing is an action applying to one topic. Understand "set [something] to [a number]" as dialing it to. Dialing it to is an action applying to one thing and one number. Understand "sell [something] for [a price]" as selling it for. Selling it for is an action applying to one price and one thing. Understand "paint [something] [a colour]" as painting it the colour. Painting it the colour is an action applying to one thing and one colour. Subsequently we will be able to refer to the player's chosen input as "the topic understood" (for text), "the number understood", "the colour understood", "the price understood", and so on. We should bear in mind that, unless we compile to Glulx, Inform will not correctly interpret a number greater than 32767, or units that equate to values larger than this. See the chapter on Units for more discussion of limits on number and unit size. 6. Held objects, multiple objects. Inform provides certain standard tokens to help us define actions that apply to more than one thing, or that imply some particular relationship between the objects named in the command. Understand "wave [something preferably held] at [something]" as waving it at. Waving it at is an action applying to one carried thing and one visible thing. The "something preferably held" token tells Inform that, in cases of ambiguity, it should prefer an object which the player already has in inventory to objects that may be visible elsewhere. It is often used in combination with actions applying to carried objects. (For more about carried, visible, and touchable objects, see the Advanced Actions chapter; for more about making the player automatically pick up objects, see the "implicitly taking" activity in the Activities chapter.) The other special tokens are largely designed to create more reasonable behavior for vague commands involving ALL: Understand "repair [things]" as repairing. Understand "wave [things preferably held]" as waving. Understand "take [things inside] from [something]" as removing it from. Understand "put [other things] into/inside/in [something]" as inserting it into. Here, for instance, we only want TAKE ALL FROM THE SILVER BOX to apply to the items that are already inside the box; and our token will ensure that this happens correctly. There are also times when we want to make our own, more flexible rules about how Inform should interpret a command from the player that uses the word ALL: for instance, we might want to automatically exclude items of scenery, or prevent the player from accidentally referring to a concealed object. For this purpose, we use not an understand rule but the "deciding whether all includes" activity. See the Activities chapter for more details. 7. Changing what the player is allowed to refer to. If we want a given action to apply to things other than the ordinary set of objects the player can see in front of him, we can use an understand rule to define this. For instance Understand "go to [any room]" as distantly approaching. Understand "find [any thing]" as seeking. Understand rules are useful to change what the player may refer to when the change of scope applies to a specific action. They are not so useful for cases where, for instance, the player is in a terrace with a view of a garden, and should be able to refer to attempt any action he likes on any item in the garden, since it's all in view. For that kind of situation, it is better to turn to the "deciding the scope of something" activity, discussed in the Activities chapter. 8. Making guesses about ambiguous commands. If we have given Inform multiple understand rules using the same first word, Inform will sort these rules from most to least specific, and will use the first line matched. Thus if we had Understand "push [open door]" as slamming. Understand "push [door]" as opening. Understand "push [something]" as pushing. Inform would use the "open door" case if possible, then the "door" case, and finally the "something" case, if the other two did not apply. This can also be used to do some guesswork about what the player intends when a command is ambiguous; if we have both of these lines Understand "eat [an edible thing]" as eating. Understand "eat [something]" as eating. Inform will try to look for an edible thing first, and only resort to an inedible object if the player's command cannot refer to anything edible. Sometimes we will want more specific control over Inform's guesses, or will want to discourage or encourage *all* actions to apply to a particular object: Does the player mean taking the great Eiffel Tower: it is very unlikely. Does the player mean tying the noun to the noun: it is unlikely. Does the player mean doing something to Lord Charisma: it is very likely. where the outcome may be any of it is very likely it is likely it is possible it is unlikely it is very unlikely In the case of multiple interpretations, Inform will accept whichever the rules deem to be likeliest. If there is no clear winner, the player will be asked which item he means. Finally, there are two activities that affect the way Inform communicates with the player about its guesses, "asking which do you mean" and "clarifying the parser's choice of something". We can use these activities to change the way Inform refers to objects when asking "which do you mean, the X or the Y?" questions, and the way it describes its guesses to the player. See the Activities chapter for more details. 9. Special effects. There are occasionally times when we will want to modify the player's line of input before attempting to understand it; we have seen one or two examples already that use the After reading a command: ... activity in order to achieve special effects. This activity is explained more fully in the activities chapter. Sometimes it is useful to remove certain punctuation marks from the player's command before interpreting it, so that for instance SAY XYZZY TO PRINCE is treated as identical with SAY "XYZZY" TO PRINCE The Punctuation Removal extension included with Inform provides several phrases to manipulate the player's command to change this sort of thing. Finally, on occasion we want to be able to record literal text used by the player, for instance when allowing the player to RECORD "PASSWORD IS FLAUBERT" IN CASE NOTEBOOK WRITE KEITH MARS ON NAMETAG and so on. Again, Inform does not by default provide resources for handling this kind of need, but there are extensions available (not included in the Inform download) that provide mechanisms to do this more easily. Chapter 17: Activities 17.1. What are activities? It is poor form to define with negatives, but the first thing to say about activities is that they are not actions. This needs saying because Inform often seems to treat them as if they are, by allowing us to write rules like so: Before printing the name of a woman, say "Ms ". With this rule in place, someone called "Daphne" will always be described as "Ms Daphne", and so on. The language looks as if we were imposing a rule on an action called "printing the name of", but there is no such action: instead, it is an "activity". To spell out the difference: An action is a simulated task for the fictional protagonist. An activity is a real task for the computer program doing the simulation. Activities allow us to influence or change some of the standard habits of Inform, using rules as flexible and powerful as those applicable to actions, though activities are in several ways simpler and easier. Example 321 (*): Ant-Sensitive Sunglasses What are activities good for? Controlling output when we want the same action to be able to produce very flexible text depending on the state of the world -- in this case, making highly variable room description and object description text. 17.2. How activities work All activities start, continue for a while and then finish: however, no activity ever runs on for more than a single turn. Several activities can be going on at the same time. For instance, suppose the following is printed as part of the description of a grocery: You can see a banana, an apple and a star-fruit here. At the moment when Inform prints "apple", two activities are under way: "listing contents of the Grocery", and "printing the name of the apple". The sequence of events was in fact: say "You can see " start listing contents of the Grocery say "a " start printing the name of the banana say "banana" finish printing the name of the banana say ", an " start printing the name of the apple say "apple" finish printing the name of the apple say " and a " start printing the name of the star-fruit say "star-fruit" finish printing the name of the star-fruit finish listing contents of the Grocery say " here." The golden rule is: if activity B starts during activity A, it must also finish during activity A. If we ever need to find out, we can always test: if the printing the name activity is going on, ... if the printing the name activity is not going on, ... but as we shall see, it's usually simpler to attach "while printing the name" provisos to rules. 17.3. Rules applied to activities The activity "printing the name of something" is the process of printing up the name of something on screen: ordinarily, this means saying the text in its "printed name" property. As with actions, rules can be attached to activities which change or augment what would normally happen. In fact the situation is simpler, because (unlike an action) an activity always finishes, so there is no question of not reaching its "after" stage. There are also only three rulebooks attached to an activity, as compared with the six affecting an action. The three rulebooks for printing the name are called "before printing the name", "for printing the name" and "after printing the name", and this is the general pattern. What happens is: 1. All "before printing the name of" rules are considered; 2. The most specific, applicable "rule for printing the name of" is considered; 3. All "after printing the name of" rules are considered. Whereas an action's later stages never take place if an early stage ends unexpectedly, an activity always goes through all three of its stages. Invoking the word "instead" in a before rule for an action will terminate not only the before rules but the whole action: the same thing for an activity will only terminate the before rules, and the for and after rules will take place as usual. The actual task is usually carried out by one single rule tucked into the back of the "for..." rulebook: it is the rule for printing the name of whatever is concerned, hence the name. Inform's standard activities are all of this pattern: they start out with no "before" or "after" rules, and just one "for" rule. 17.4. While clauses Rules applied to actions can become baroque ("after going through a door in the presence of an animal when -" and so on and so forth), but activities are again simpler: they only have one possible clause attached, which is called "while". For instance, the following would provide a fairly sledgehammer hint that the sack should not lightly be thrown away: The sack is a player's holdall. The sack is carried. Rule for printing the name of the sack while the sack is not carried: say "your abandoned sack". Any condition can be given after the "while", and we can also specify that another activity has to be going on. Thus: Rule for printing the name of the lemon sherbet while listing contents: say "curious sort of lemon sherbet sweet". This nicely distinguishes between contexts where it's appropriate to be more verbose, and where it isn't. Thus: You can see a teaspoon and a curious sort of lemon sherbet sweet here. > TAKE ALL teaspoon: Taken. lemon sherbet: Taken. 17.5. New activities Activities are all about influencing the standard mechanisms which Inform uses, so it might at first seem that there is no need to create new activities: but on further reflection, quite a lot of the writing of interactive fiction involves creating new and systematic ways to do things, and as soon as we have a general rule, we will want to have exceptions. Inform therefore allows us to create our own activities, giving us ways to influence the operation of our own mechanisms. There are two kinds of activity: those which relate to a specific value (usually an object but not necessarily), and those which do not. Here are some examples of activities being created: Assaying is an activity. Analysing something is an activity. Announcing something is an activity on numbers. Inform looks for the clue "something" (or "of something") after the activity's name to see if it will work on a value: so analysing and announcing will do, but assaying won't. If we don't specify a kind, Inform assumes the value will be an object, as if we had written: Analysing something is an activity on objects. As always in Inform, the names of activities are themselves values. "assaying activity" has kind activity on nothing "analysing activity" has kind activity on objects "announcing activity" has kind activity on numbers Creating an activity is like creating an action: it automatically makes new rulebooks - "before analysing", "for analysing" and "after analysing" - but they start out empty, so the activity does nothing yet. Just as it does for rulebooks, Inform defines the adjectives "empty" and "non-empty" for activities to test this state: if the analysing activity is empty, ... will be true only when all three of its rulebooks are empty. A newly created activity never happens unless we take steps to make it do so. We can make an activity happen at any time by writing phrases like so:

carry out the (activity) activity
This phrase carries out the given activity, which must be one not applying to any value. Example: carry out the assaying activity;

carry out the (activity on values) activity with (value)
This phrase carries out the given activity, which must apply to a kind of value matching the one supplied. Example: carry out the analysing activity with the pitchblende; carry out the announcing activity with the score;
To make the activity do something useful, we need to put a rule into its "for" rulebook: Rule for announcing a number (called N): say "Ladies and gentlemen, [N]." The last for assaying rule: say "Professionally, you cast an eye around mineral deposits nearby, noticing [list of rocks in the location]." "The last" is a technicality about rulebooks (see the next chapter) which, put briefly, guarantees that this rule comes last among all possible "for assaying" rules. This is good form because the whole point of an activity is to make it easy for further rules to interfere - so we deliberately hang back to last place, giving precedence to anybody else who wants it. The "for" rulebook is one where rules stop the activity, by default, when they take effect - in the same way that the "instead" rules stop actions by default. If this causes problems, we can use:

continue the activity
This phrase should be used only in rules in activity rulebooks. It causes the current rule to end, but without result, so that the activity continues rather than stopping as a result of the rule. This is useful for rulebooks (like the "for" rulebook of an activity) where the default is that a rule does stop the activity.
Activities are more useful than they first appear. Every new one provides a context which other activities can observe. We could, for instance, define Rule for printing the name of a rock while assaying: ... so that during assays more technical names are used. Example 322 (**): AARP-Gnosis An Encyclopedia set which treats volumes in the same place as a single object, but can also be split up. Example 323 (***): Aftershock Modifying the rules for examining a device so that all devices have some specific behavior when switched on, which is described at various times. Example 324 (***): Crusoe Adding a "printing the description of something" activity. 17.6. Activity variables Just as actions can have variables, which are created when the action starts and disappear when it finishes, so activities can also have variables. They are visible to the rules for that activity, and nowhere else. (If the activity should happen a second time within its first run, that second occurrence gets its own copy of the variable, leaving the original untouched.) Typically it will be useful to set a variable to some default value at the "before" stage, calculate some interesting value for it in the "for" stage, and make use of the outcome during the "after" stage. For instance: Analysing something is an activity. The analysing activity has a text called first impression. Instead of examining something (called the sample), carry out the analysing activity with the sample. Before analysing: now the first impression is "unremarkable". Rule for analysing someone: now the first impression is "living tissue". After analysing something (called the sample): say "Your professional opinion of [the sample] is that it is [first impression]." 17.7. Beginning and ending activities manually If we have declared a new activity, like "analysing", the normal way to make it happen would be to write carry out the analysing activity with the pitchblende; which goes through the whole machinery of rules - before, for, after - and then resumes, the activity having started, taken place and come to an end. But there are times when it is not convenient to write a suitable "for ..." rule, or where we need more control, and do not wish to hand the whole business over to a single phrase. For such times we are allowed to write:

begin the (activity) activity
This phrase causes the named activity to become active, and runs its "before" rulebook. The activity must be one which applies to nothing. Example: begin the assaying activity; In all cases a matching "end the ... activity" or else "abandon the ... activity" phrase must be reached.

begin the (activity on values) activity with (value)
This phrase causes the named activity to become active, and runs its "before" rulebook. The activity must be one which applies to a value of a matching kind. Example: begin the analysing activity with the pitchblende; In all cases a matching "end the ... activity with ..." or else "abandon the ... activity with..." phrase must be reached.
And when we are done:

end the (activity) activity
This phrase runs the "after" rulebook of the activity and then causes it to become inactive. The activity must be one which applies to nothing. Example: end the assaying activity; This must only happen to match an earlier "begin the ... activity" phrase.

end the (activity on values) activity with (value)
This phrase runs the "after" rulebook of the activity and then causes it to become inactive. The activity must be one which applies to a value of a matching kind. Example: end the analysing activity with the pitchblende; This must only happen to match an earlier "begin the ... activity with..." phrase.
So the usual structure is like so: begin the analysing activity with the pitchblende; ... end the analysing activity with the pitchblende; This time the activity is ongoing throughout as many phrases as we care to write between the "begin" and "end". The before rules are considered at the time of the "begin ..." phrase; the after rules at the "end ...". What, then, of the "for" rules? In the above setup, they would simply be ignored. But we can make them effectual thus begin the analysing activity with the pitchblende; ... if handling the analysing activity with the pitchblende: ... ... end the analysing activity with the pitchblende; We place the activity's normal behaviour inside the "if"; the condition, "if handling...", is true only if no rule has intervened. This means that we (or other authors using our activity) can create their own for rules to substitute here. If we elsewhere write Rule for handling the analysing activity with the pitchblende when the player is not sober: say "You can't seem to focus." that rule will intervene and take the place of whatever we have placed inside the condition.

if handling (activity) activity:
This condition is true if the given activity is going on and no rule intervenes in the handling of that activity. The activity must be one which doesn't apply to any value.

if handling (activity on values) activity with (value):
This condition is true if the given activity is going on and no rule intervenes in the handling of that activity. The given value is the one it is being applied to.
It is also legal to force an early end to an activity with:

abandon the (activity) activity
This phrase ends an activity at once (without consulting any further rulebooks, including its "after" rulebook). It can only be used with an activity which has had its "begin" but not yet its "end" phrase; it is a drastic remedy best taken only if it is clear that circumstances have changed so that the activity now seems inappropriate. It must not be used during one of the rules for the activity: it can only be used between the begin and for stages, or between the for and end stages. abandon the assaying activity;

abandon the (activity on values) activity with (value)
This phrase ends an activity at once (without consulting any further rulebooks, including its "after" rulebook). It can only be used with an activity which has had its "begin" but not yet its "end" phrase; it is a drastic remedy best taken only if it is clear that circumstances have changed so that the activity now seems inappropriate. It must not be used during one of the rules for the activity: it can only be used between the begin and for stages, or between the for and end stages. abandon the analysing activity with the pitchblende;
We need to follow three golden rules: all activities must end, they must never last longer than a turn, and if activity B starts during activity A then it must also finish during activity A. We must also be careful to make sure that if an activity applies to something, then it begins and ends with the same something (the pitchblende, in the above example). 17.8. Introduction to the list of built-in activities Activities tend to be about process, rather than outcome. Many of the things Inform does - printing up lists of items, reading commands from the keyboard, and so on - are done as activities, because that way the process can be nudged a little. Too many works of interactive fiction betray their mechanical nature by making it visible that the general machinery being used does not quite seem natural for this or that situation. Activities enable us to add the many graceful touches which avoid that: which contribute nothing to a work, and also everything. The rest of this chapter covers every activity built in to Inform, with one section for each. It is intended primarily for reference, but may be worth skimming through at a first reading, to give a sense of the possibilities. 17.9. Deciding the concealed possessions of something 1. When it happens. Frequently - whenever Inform needs to check whether something is visible or not. Nothing should be printed, and the activity needs to run quickly, so it should not (for instance) calculate best routes through complicated maps before getting an answer. 2. The default behaviour. There is no concealment. The ordinary rules still apply, though: the contents of a closed opaque container are invisible because there is a barrier in the way which cannot be seen through, even though nobody is "concealing" anything. 3. Examples. To repeat a number of brief examples given at the end of Chapter 3, where this activity made an early appearance: Rule for deciding the concealed possessions of the Cloaked Villain: if the particular possession is the sable cloak, no; otherwise yes. The coin is in the Roman Villa. The face and inscription are parts of the coin. Rule for deciding the concealed possessions of the coin: if the coin is carried, no; otherwise yes. The value "particular possession" is the one whose concealment is in question, of course. We can ignore this if someone is invariably secretive: Rule for deciding the concealed possessions of the furtive ghost: yes. Example 325 (*): Hays Code Clark Gable in a pin-striped suit and a pink thong. 17.10. Printing the name of something 1. When it happens. Whenever the name of a thing or room is printed. 2. The default behaviour. For items other than the current player, the "printed name" property is printed out; but for the current player, "you" or "yourself" is printed. (That doesn't necessarily mean that the "printed name" of the player is never used. Suppose there are two people, Alice and Bob, and the narrative switches between them: when Alice is the player, she appears as "yourself" but Bob is "Bob"; but when Bob is the player, he is "yourself" and Alice is "Alice".) 3. Examples. (a) A pen which is described differently in inventories: Rule for printing the name of the pen while taking inventory: say "useful pen". "Taking inventory" is a condition which is true if that's the current action and not otherwise, so the effect is that the pen is called "a useful pen" only in inventory listings. "While looking" is a similarly useful one. (b) Italicising the names of novels: A novel is a kind of thing. Dr Zhivago and Persuasion are novels. Before printing the name of a novel, say "[italic type]". After printing the name of a novel, say "[roman type]". (c) Telling the time: After printing the name of the wrist watch while taking inventory: say " (time: [the time of day])". (d) Merging containers with their contents: Rule for printing the name of the bottle while not inserting or removing: if the bottle contains sand, say "bottle of sand"; otherwise say "empty bottle"; omit contents in listing. This example makes use of a special phrase:

omit contents in listing
This phrase changes the form of an inventory listing, room description, etc., so that it will simply list "a bottle of sand" or "an empty bottle", rather than "a bottle (in which is sand)" or "a bottle (which is empty)". It should be used only when the listing is imminent, and does not have permanent effect.
The clause about not inserting or removing is to prevent messages like "You put the sand in the bottle of sand.", where it's confusing to refer to the bottle as anything other than "the bottle". Example 326 (*): Shipping Trunk A box of baking soda whose name changes to "completely ineffective baking soda" when it is in a container with something that smells funny. Example 327 (**): Trachypachidae Maturin 1803 Bottles with removable stoppers: when the stopper is in the bottle, the bottle is functionally closed, but the stopper can also be removed and used elsewhere. Descriptions of the bottle reflect its state intelligently. Example 328 (****): Chronic Hinting Syndrome Using name-printing rules to keep track of whether the player knows about objects, and also to highlight things he might want to follow up. 17.11. Printing the plural name of something 1. When it happens. Only when a group of identical items is present in the same place, and are being described jointly with text like "You can see five gold rings here." The activity happens after "five" and before "here." (See the activity "printing a number of something" if the whole phrase needs to be altered.) 2. The default behaviour. The plural name - in this case "gold rings" - is printed out. 3. Examples. (a) Suppose we want to emphasise how nice it is to have more than one gold ring: Rule for printing the plural name of a gold ring: say "gleaming gold rings". (b) If the number needs changing as well, it's necessary to use the "printing a number of something" activity instead. Example 329 (**): Hudsucker Industries Letters which are described differently as a group, depending on whether the player has read none, some, or all of them, and on whether they are alike or unlike. 17.12. Printing a number of something 1. When it happens. Only when a group of identical items is present in the same place, and are being described jointly with text like "You can see five gold rings here." The activity prints the "five gold rings" part. The variable "listing group size" contains the number, which in this example would be 5, and is always at least 2. 2. The default behaviour. The number of items is printed, in words ("five") and then the "printing the plural name" activity is run ("gold rings"). 3. Examples. (a) Using this activity is for perfectionists, because the normal behaviour is almost always fine. Still: Rule for printing a number of blocks when the listing group size is 3: say "all three blocks". (b) Or perhaps: Rule for printing a number of ants: say "altogether [listing group size in words] ants". (c) If the only part needing variation is the plural name, it's simpler and tidier to use the "printing the plural name of something" activity instead. Example 330 (*): Prolegomena Replacing precise numbers with "some" or other quantifiers when too many objects are clustered together for the player to count at a glance. 17.13. Listing contents of something 1. When it happens. When taking inventory, the list is produced by the activity "listing contents of yourself"; when looking, a list of items which do not deserve their own paragraphs is produced by "listing contents of" the location. (But note that it doesn't happen when, for instance, "[a list of animals]" is printed, because that isn't a list of the contents of any room or location.) 2. The default behaviour. The list is printed out. 3. Examples. (a) We have already seen that it can be elegant to elaborate on a description in the context of a list. Here we add "discarded" to a sweet wrapper which is found on the ground. Rule for printing the name of the wrapper while listing contents of a room: say "discarded sweet wrapper". (b) Lists can be considerably shortened and tidied up if similar items are grouped together. We do this by specifying what should be grouped together before listing contents, using the special phrase "group ... together": Utensil is a kind of thing. The knife, the fork and the spoon are utensils. Before listing contents: group utensils together as "utensils". The result will be, say, "two utensils (knife and spoon)", if both are found in the same place. (c) We can less obtrusively group items together like so: Before listing contents while taking inventory: group utensils together. Three special phrases exist for this kind of list organisation:

group (description of objects) together
This phrase causes the objects described to be listed together in a single item as part of an inventory or room description. The effect is temporary, and the phrase should only be used when this list is imminent. Example: Utensil is a kind of thing. The knife, the fork and the spoon are utensils. Before listing contents: group utensils together. This might produce the list item "fork and spoon".

group (description of objects) together giving articles
This phrase causes the objects described to be listed together in a single item as part of an inventory or room description, but giving each individual item its indefinite article. The effect is temporary, and the phrase should only be used when this list is imminent. Example: Utensil is a kind of thing. The knife, the fork and the spoon are utensils. Before listing contents: group utensils together giving articles. This might produce the list item "a fork and a spoon".

group (description of objects) together as (text)
This phrase causes the objects described to be listed together in a single item as part of an inventory or room description, summarised with the given text. The effect is temporary, and the phrase should only be used when this list is imminent. Example: Utensil is a kind of thing. The knife, the fork and the spoon are utensils. Before listing contents: group utensils together as "utensils". This might produce the list item "two utensils (fork and spoon)".
Example 331 (*): Unpeeled Calling an onion "a single yellow onion" when (and only when) it is being listed as the sole content of a room or container. 17.14. Grouping together something 1. When it happens. Only while listing contents, and only when a collection of items to be grouped together is reached. This in turn happens only if a "before listing contents" rule has chosen it (see previous section). The first item in the group is the one to which the activity formally applies. The variable "listing group size" gives the number of items grouped together in this way. 2. The default behaviour. The items grouped together are printed in an English phrase, such as "egg, chicken and farmer". In particular, they are not split onto separate lines even if the rest of the list is. (See previous section.) 3. Examples. (a) Here are Scrabble pieces which are described as "the tile W from a Scrabble set" or similar outside of lists, but which, when they turn up together in lists, are rolled together into "the tiles A, B and D from a Scrabble set". A Scrabble piece is a kind of thing. The X, the Y and the Z are Scrabble pieces. Before listing contents: group Scrabble pieces together. Before printing the name of a Scrabble piece while not grouping together, say "tile ". After printing the name of a Scrabble piece while not grouping together, say " from a Scrabble set". Before grouping together Scrabble pieces, say "the tiles ". After grouping together Scrabble pieces, say " from a Scrabble set". (b) Maybe we only want an abbreviated form when there are five or more tiles in one place: A Scrabble piece is a kind of thing. The X, the W, the F, the Y and the Z are Scrabble pieces in the Lounge. Before listing contents: group Scrabble pieces together. Before grouping together Scrabble pieces when the listing group size is greater than 4: say "some [listing group size in words] tiles (". After grouping together Scrabble pieces when the listing group size is greater than 4: say ") from a Scrabble set". (c) We can throw out all pretence at listing and say whatever we like, in fact: Before listing contents while taking inventory: group utensils together. Rule for grouping together utensils: say "the usual utensils". 17.15. Printing room description details of something 1. When it happens. When an item is listed in the miscellaneous collection of items present in a room (the ones which do not deserve their own paragraphs): this is normally the last paragraph of a room description. 2. The default behaviour. A bracketed piece of extra information is added for certain items such as containers: You can also see Po and a cage (empty) here. The " (empty)" (note initial space) was added by this activity. (Note that this activity is not responsible for describing further items visible because of the item in question: that is, it does not print the text such as "(in which is a notepad)" which would appear if there were contents. If we want to remove such text, we should use "omit contents in listing": see the activity "for printing the name of something".) 3. Examples. (a) To get rid of such addenda entirely, try: Rule for printing room description details: stop. (b) To add a new form of addendum: Rule for printing room description details of a person: say " (at last, someone to talk to)" instead. If both examples (a) and (b) are in place at once, we might now read: You can also see Po (at last, someone to talk to) and a cage here. Example 332 (*): Rules of Attraction A magnet which picks up nearby metal objects, and describes itself appropriately in room descriptions and inventory listings, but otherwise goes by its ordinary name. 17.16. Printing a refusal to act in the dark 1. When it happens. When an action which requires light is tried, and the visibility rules decide that not enough light is present. 2. The default behaviour. To print "It is pitch dark, and you can't see a thing." 3. Examples. (a) This might do for some twilit, penumbral room: Rule for printing a refusal to act in the dark: if we are examining something, say "It's not totally dark here, perhaps, but certainly too dim for close-up examination of anything." instead. Example 333 (***): Zorn of Zorna Light levels vary depending on the number of candles the player has lit, and this determines whether or not he is able to examine detailed objects successfully. 17.17. Printing the announcement of darkness 1. When it happens. Inform frequently calculates to see if the player is in light or darkness: this activity happens on the change from light to darkness. 2. The default behaviour. To print "It is now pitch dark in here!". 3. Examples. (a) The most obvious use is to change the text: Rule for printing the announcement of darkness: say "Ooh-er! It's now very nearly pitch dark in here." instead. (b) But we could also use this activity for sneakier purposes, silently moving things around: Before printing the announcement of darkness: now all of the gremlins are in the kitchen. (c) A special description for occasions when the player has climbed into a container and shut it (so that the darkness is the result of his own actions, rather than some external circumstance): Rule for printing the announcement of darkness when closing a container which contains the player: say "Congratulations: now you can't see a thing." instead. 17.18. Printing the announcement of light 1. When it happens. Inform frequently calculates to see if the player is in light or darkness: this activity happens on the change from darkness to light. 2. The default behaviour. To try the looking action, which usually prints up a room description. 3. Examples. (a) Perhaps the player is initially too disoriented to look around in any coherent way: Rule for printing the announcement of light in the Dazzling Temple: say "You are almost blinded by the suffusion of white light, and have spots before your eyes." instead. 17.19. Printing the name of a dark room 1. When it happens. When looking in darkness, or writing the (default) status line in darkness. 2. The default behaviour. To print "Darkness". 3. Examples. (a) One might modify the darkness with some adjective: Before printing the name of a dark room, say "Near ". (Note that this activity does not come in different forms for different dark rooms: the wording is fixed at "printing the name of a dark room", and we are not allowed to substitute particular dark rooms or assign a "(called ...)" onto the mention of the dark room.) 17.20. Printing the description of a dark room 1. When it happens. When looking in darkness. 2. The default behaviour. To print "It is pitch dark, and you can't see a thing." 3. Examples. (a) A simple variation of wording: Rule for printing the description of a dark room: say "Your eyes can barely make anything out." instead. (b) More stylishly, Rule for printing the description of a dark room: try listening instead. which produces, for instance, Darkness You hear nothing unexpected. (Note that this activity does not come in different forms for different dark rooms: the wording is fixed at "printing the description of a dark room", and we are not allowed to substitute particular dark rooms or assign a "(called ...)" onto the mention of the dark room.) Example 334 (**): Hohmann Transfer Changing the way dark rooms are described to avoid the standard Inform phrasing. Example 335 (***): Four Stars An elaboration of the idea that when light is absent, the player should be given a description of what he can smell and hear, instead. 17.21. Constructing the status line 1. When it happens. Just before input is accepted from the keyboard, Inform constructs a "status line" at the top of the window which is normally displayed in reverse colours (white on black instead of black on white, say). 2. The default behaviour. Makes the status line up out of two pieces, the "left hand status line" and the "right hand status line". Since these can freely be changed, note that the status line is already very customisable without using rules applied to this activity. 3. Examples. (a) The most useful thing about this activity is that it allows us to vary descriptions in the status line. This is especially helpful to abbreviate unduly long room names, which might not otherwise fit: The Temple Of A Thousand Mightily Peeved Deities is a room. Rule for printing the name of the Temple while constructing the status line: say "Temple". (b) Again, it's usually not necessary to apply activity rules to this, but occasionally amusing effects are possible if we do: The blindfold is wearable and carried. Rule for constructing the status line while the blindfold is worn: do nothing. Example 336 (*): Ways Out A status line that lists the available exits from the current location. Example 337 (**): Guided Tour A status line that lists the available exits from the current location, changing the names of these exits depending on whether the room has been visited or not. 17.22. Writing a paragraph about 1. When it happens. Just before writing a paragraph about some item in a room description. 2. The default behaviour. Is to do nothing. However, if a rule is supplied which prints something up, then this replaces the paragraph which would otherwise have been printed. Moreover, any items whose names are said in the course of this rule - for instance, by being listed - are then excluded from the remainder of the room description, because they are considered as having been described sufficiently already. Warning: because we often want a "for" rule for this activity to make some calculation and then possibly choose to do nothing (see the example "Otranto"), Inform suppresses the usual paragraph not when a "for" rule took effect but when it detected a paragraph having been printed. This can get confused if a text substitution affecting paragraph breaks, say "[line break]", is within the final "say" of a "for writing a paragraph about" rule. 3. Examples. (a) This is a neat way to wrap several things together into the same paragraph: Rule for writing a paragraph about Mr Wickham: say "Mr Wickham looks speculatively at [list of women in the location]." because now "Mr Wickham looks speculatively at Velma and Daphne" will now prevent the appearance of the subsequent text "You can also see Velma and Daphne." Inform keeps track of which objects have already been named with an either/or property called "mentioned", which it assigns whenever the name of an object has been automatically printed. So in this case, Velma and Daphne are now mentioned. Note "automatically printed", though: if the text printed had just been "Mr Wickham looks speculatively at Velma and Daphne", rather than the text-substitution list used above, then Inform would not know that Velma and Daphne have been described. If we ever need to override this - say, we want to list all the women but make sure that Velma gets another paragraph anyway - we could change Velma to unmentioned again after the listing. Example 338 (*): Reflections Emphasizing the reflective quality of shiny objects whenever they are described in the presence of the torch. Example 339 (**): Emma Social dynamics in which groups of people form and circulate during a party. Example 340 (****): Air Conditioning is Standard Uses "writing a paragraph about" to make person and object descriptions that vary considerably depending on what else is going on in the room, including some randomized NPC interactions with objects or with each other. 17.23. Listing nondescript items of something 1. When it happens. This activity prints up the also-ran paragraph at the end of a room description. These are nondescript items because they don't merit paragraphs of their own: if, as sometimes happens, there are none in the room, then no such paragraph is printed and this activity does not happen. (So to add a further paragraph to a room description, a simpler "after looking" rule should be used, not an "after listing nondescript items" rule.) 2. The default behaviour. The paragraph ordinarily reads as "You can also see a cask and a clock." or similar. Before the activity begins, those objects which are nondescript - in this case the cask and the clock - are given the property of being "marked for listing". If it turns out that nothing is marked for listing, because of before rules like the one in the example below, then nothing is printed. 3. Examples. (a) Promoting something out of the nondescript category, by unmarking it. Before listing nondescript items: if the watch is marked for listing: say "The watch catches your eye."; now the watch is not marked for listing. (b) Changing the normal phrasing of the paragraph. Note that we can also change the listing style; the one below is the default. Rule for listing nondescript items of the Distressingly Messy Room: say "Strewn carelessly on the floor"; list the contents of the Distressingly Messy Room, as a sentence, tersely, listing marked items only, prefacing with is/are, including contents and giving brief inventory information; say "." Example 341 (*): Rip Van Winkle A simple way to allow objects in certain places to be described in the room description body text rather than in paragraphs following the room description. Example 342 (**): Happy Hour Listing visible characters as a group, then giving some followup details in the same paragraph about specific ones. Example 343 (**): The Eye of the Idol A systematic way to allow objects in certain places to be described in the room description body text rather than in paragraphs following the room description, and to control whether supporters list their contents or not. 17.24. Printing the locale description of something 1. When it happens. A "locale description" is Inform jargon for the part of a room description which catalogues the visible items in the room. When looking, Inform will normally print the description of the room itself, followed by a locale description for the room. But if the player is in a cage in the room, there will be two locale descriptions: one for the room, then another for the cage. This activity is used to write the locale description for a single domain, and the "something" can be either a room, an enterable container, or an enterable supporter. 2. The default behaviour. Is quite complicated, and is written up in full in the typeset form of the Standard Rules downloadable from the Inform website. Briefly, though: we first run the "choosing notable locale objects" activity to find out what ought to be mentioned here. That assembles a list of things to mention, sorted into priority order. Items with priority 1 go first, then those with priority 2, and so on. The "printing a locale paragraph" activity is run for each, and in practice that usually hands the job over to "writing a paragraph about". Sometimes a paragraph will indeed be written, but not always. Sometimes there is nothing interesting to say, and an item is left until a final, single paragraph which gathers up the leftovers ("You can also see a scarlet fish, a harmonium and a kite here."), the printing of which is done by the "listing nondescript items of" activity. As soon as any item picks up the either/or property "mentioned", by having its name printed, it is struck out so that it will not appear subsequently, whatever its priority. 3. Examples. As general advice: if the effect wanted can be got using "writing a paragraph about" and "listing nondescript items of" alone, use those; if it's necessary to meddle further, use "choosing notable locale objects" and "printing a locale paragraph" to alter the normal processes; use the all-powerful "printing the locale description" activity only when the whole process needs to be altered, not the item-by-item workings. (a) In the Very Misty Moorlands, nothing on the ground can ordinarily be seen through the swirling mist, so the locale description is suppressed entirely: Rule for printing the locale description of the Very Misty Moorlands: say "Mist coils around your feet, thick as a blanket. You cannot even see the ground you walk upon." instead. Report taking something in the Very Misty Moorlands: say "You grope blindly in the mist and pick up [the noun]." instead. (b) Here we take the chance to insert an additional paragraph into the locale description. This does relate to an item which might be described later, but where the player doesn't know that: The Horological Workshop is a room. The marble table is fixed in place in the Workshop. The parcel is a closed opaque container on the marble table. The alarm clock is a device in the parcel. The alarm clock is switched on. Before printing the locale description of a room (called the setting): if the setting encloses the alarm clock and the alarm clock is switched on, say "A faint ticking noise can be heard." Example 344 (*): Priority Lab A debugging rule useful for checking the priorities of objects about to be listed. 17.25. Choosing notable locale objects for something 1. When it happens. See "printing the locale description". This activity is expected to decide which items ought to be mentioned in a locale description for a given room, enterable container or enterable supporter, and to give each item a priority, which is a number ranging upwards from 1 (which is the top priority). The lower the priority number, the earlier the mention, or at least, the earlier the opportunity to be mentioned: it's up to other activities whether to give it a paragraph of its own or not. This activity only makes something a candidate, and decides what order the candidates will be tried in. 2. The default behaviour. By default, this activity contains only the "standard notable locale objects rule". This chooses exactly those items directly contained by the locale, assigning all of them priority 5. Note that this includes scenery, and other probably unwanted items - those will be excluded later. 3. Examples. (a) In the Misty Moorlands, only large items on the ground are visible through the mist: A thing can be large or small. A thing is usually small. The stepladder is a large thing in the Misty Moorlands. Rule for choosing notable locale objects for the Misty Moorlands: repeat with item running through large things in the Misty Moorlands: set the locale priority of the item to 5. Report taking a small thing in the Misty Moorlands: say "You grope blindly in the mist and pick up [the noun]." instead. Note the special phrase set the locale priority of the item to 5; which should be used only in rules for locale activities. It makes the given item a candidate and sets its priority. (Setting the priority to 0 forces an item not to be a candidate, and can thus undo the effect of previous rules.) Example 345 (*): Low Light An object that is only visible and manipulable when a bright light fixture is on. Example 346 (***): Casino Banale Creating room descriptions and object descriptions that change as the player learns new facts and pieces things together. 17.26. Printing a locale paragraph about 1. When it happens. See "printing the locale description". By this point, the locale description process has identified a number of items as candidates to be described, and worked out a priority order. This activity is then called for each candidate in turn, starting with the highest priority items and working downwards. It can either print some text or not, and can either mark the item as "mentioned" or not: if it does, then the item won't appear subsequently in the locale description. If the activity does nothing, the item becomes "nondescript" and falls through into the final "You can also see..." paragraph, unless another rule mentions it in the mean time. 2. The default behaviour. Is provided by a sequence of seven rules: (1) The "don't mention player's supporter in room descriptions rule" excludes anything the player is directly or indirectly standing on or, less frequently, in. The header of the room description has probably already said something like "Boudoir (on the four-poster bed)", so the player can't be unaware of this item. (2) The "don't mention scenery in room descriptions rule" excludes scenery. (3) The "don't mention undescribed items in room descriptions rule" excludes the player object. (It's redundant to say "You can also see yourself here.") At present nothing else in I7 is "undescribed" in this sense. (4) The "set pronouns from items in room descriptions rule" adjusts the meaning of pronouns like IT and HER to pick up items mentioned. Thus if a room description ends "Mme Tourmalet glares at you.", then HER would be adjusted to mean Mme Tourmalet. (5) The "offer items to writing a paragraph about rule" gives the "writing a paragraph about" activity a chance to intervene. We detect whether it does intervene or not by looking to see if it has printed any text. (6) The "use initial appearance in room descriptions rule" prints the "initial appearance" property of an item which has never been handled as a paragraph, if it has one. (7) The "describe what's on scenery supporters in room descriptions rule" is somewhat controversial. It prints text such as "On the mantelpiece is a piece of chalk." for items which, like the mantelpiece, are scenery mentioned - we assume - in the main room description. (It is assumed that scenery supporters make their contents more prominently visible than scenery containers, which we do not announce the contents of.) 3. Examples. If all that's required is to supply an interesting paragraph of room description about something then it's always better to use the "printing a paragraph about" activity, not this one. This activity should only be used when the mechanism itself needs to be adjusted. (a) The following excludes doors from room descriptions: For printing a locale paragraph about a door (called the item) (this is the don't mention doors in room descriptions rule): set the locale priority of the item to 0; continue the activity. (It's usually a good idea to "continue the activity" at the end of rules for this activity, since usually they all need to take effect for a happy outcome to the process. Here it doesn't really matter, since we were trying to stop anything from happening about the door, but it doesn't do any harm either.) (b) Here's how to abolish what may be the most contentious rule in the whole Standard Rules: The describe what's on scenery supporters in room descriptions rule is not listed in any rulebook. Example 347 (*): Kiwi Creating a raised supporter kind whose contents the player can't see or take from the ground. Example 348 (***): Copper River Manipulating room descriptions so that only interesting items are mentioned, while objects that are present but not currently useful to the player are ignored. 17.27. Deciding the scope of something 1. When it happens. "Scope" is a term of art in interactive fiction programming: it means the collection of things which can be interacted with at any given moment, which depends on who you are and where you are. Commands typed by the player will only be allowed to go forward into actions if the things they refer to are "in scope". Inform also needs to determine scope at other times, too: for instance, when deciding whether a rule conditional on being "in the presence of" something is valid. It is a bad idea to say anything during this activity. 2. The default behaviour. Is complicated: see the Inform Designer's Manual, 4th edition, page 227. Briefly, the scope for someone consists of everything in the same place as them, unless it is dark. 3. Examples. (a) We very rarely want to forbid the player to refer to things close at hand, but often want to allow references to distant ones. For instance, a mirage of something which is not present at all: After deciding the scope of the player while in the Shrine: place the holy grail in scope. Two different phrases enable us to place unusual items in scope:

place (object) in scope
This phrase should only be used in rules for the "deciding the scope of..." activity. It places the given object in scope, making it accessible to the player's commands, regardless of where it is in the model world. Examples: place the distant volcano in scope; place the lacquered box in scope, but not its contents; Ordinarily if something is placed in scope, then so are its parts and (in the case of a supporter or a transparent or open container) its contents; using the "but not its contents" option we can place just the box itself in scope.

place the/-- contents of (object) in scope
This phrase should only be used in rules for the "deciding the scope of..." activity. It places the things inside or on top of the given object in scope, making them accessible to the player's commands, but it does nothing to place the object itself in scope. (It might of course be in scope anyway, and if it is then this phrase won't remove it.) Example: place the contents of the lacquered box in scope; place the contents of the Marbled Steps in scope; Note that the object in question can be a room, as in this second example.
(b) Another useful device is to be able to see, but not touch, another room: The Cloakroom is a room. "This is just a cloakroom, but through a vague, misty mirror-window you can make out the Beyond." After looking in the Cloakroom, say "In the mirror you can see [list of things in the Beyond]." After deciding the scope of the player while in the Cloakroom: place the Beyond in scope. The Beyond is a room. Johnny Depp is a man in the Beyond. (This must, however, also be a mirage, as at time of writing Mr Depp is alive and as well as can be expected following the reviews of "Charlie and the Chocolate Factory".) When a room is placed in scope, this is understood as placing its contents in scope rather than the room-object itself. So "place the Ballroom in scope" allows the player to talk about the dancers, the chamber musicians and so forth, but not to "EXAMINE BALLROOM" as such. (This is sensible because actions like examining apply to things: and a room, unlike a container or a supporter, is not a kind of thing.) (c) In darkness, the scope of someone is ordinarily restricted to his or her possessions (and body), but we can override that: After deciding the scope of the player while in darkness: place the location in scope. 4. A note about actions. This activity takes place during the process of understanding the player's command, when the action that will take place is not fully known. So if the player types "TAKE SHOEBOX", this activity would happen when SHOEBOX is being examined for meaning. Inform knows the action it would be taking if the current line of command grammar were to be accepted, but it does not yet know to what objects that command would be applied. That means attaching a proviso like "... while taking a container" to a rule for this activity will cause the rule to have no effect - whereas "... while taking" would be fine. Example 349 (*): Peeled Two different approaches to adjusting what the player can interact with, compared. Example 350 (*): Scope for listening different from scope for seeing Using "deciding the scope" to change the content of lists such as "the list of audible things which can be touched by the player". Example 351 (**): Ginger Beer A portable magic telescope which allows the player to view items in another room of his choice. Example 352 (**): Rock Garden A simple open landscape where the player can see between rooms and will automatically move to touch things in distant rooms. Example 353 (***): Stately Gardens An open landscape where the player can see landmarks in nearby areas, with somewhat more complex room descriptions than the previous example, and in which we also account for size differences between things seen at a distance. 17.28. Clarifying the parser's choice of something 1. When it happens. When the player has typed an ambiguous noun reference, and Inform has made a decision about what was meant, and it matters what this decision is. (If the decision is between three identical gold coins, say, then it doesn't matter, and this activity does not take place.) 2. The default behaviour. Text in brackets such as "(the laminated mahogany box)" is printed, on its own line. 3. Examples. (a) In the following, asking to TAKE TOWER results in the parser choosing the souvenir model (because of the "does the player mean..." rule making the alternative unlikely), and then explaining itself by saying "(The little one, obviously.)" instead of "(the souvenir model Eiffel Tower)". The Champs du Mars is a room. The great Eiffel Tower is here. "The great Tower stands high over you." The souvenir model Eiffel Tower is here. "Comparatively tiny is the souvenir version." The great Eiffel Tower is fixed in place. Does the player mean taking the great Eiffel Tower: it is very unlikely. Rule for clarifying the parser's choice of the model tower: say "(The little one, obviously.)" 4. A note about actions. This activity takes place during the process of understanding the player's command, when the action that will take place is not fully known. So if the player types "TAKE SHOEBOX", this activity would happen when SHOEBOX is being examined for meaning. Inform knows that the action will be taking, but nothing else. That means attaching a proviso like "... while taking a container" to a rule for this activity will cause the rule to have no effect - whereas "... while taking" would be fine. 17.29. Asking which do you mean 1. When it happens. When the player has typed an ambiguous noun reference, and Inform has not been able to decide what was meant. 2. The default behaviour. A question such as "Which do you mean, the laminated mahogany box or the boom box?" is printed. (This activity shapes the question: it is not responsible for parsing the answer. It would be very mysterious to write rules for this activity such that nothing is printed, because the player would then have no idea what to type.) 3. Examples. The question is harder to print than may first appear, since one must not simply list the options, but also take into account collections of plural objects ("Which do you mean, the gold-tipped pen or a gold coin?"). It is probably better not to try to rewrite this. (a) But we can place notes before or after: here is a verbose explanation for beginners to IF. Before asking which do you mean: say "Okay, so I'm going to have to ask a question now: you've typed something ambiguous, and I don't know which noun you're referring to." After asking which do you mean: say "(Just type a word or two to give me more information.)" (b) We can also use this activity as a context for other activities. For instance: The Champs du Mars is a room. The great Eiffel Tower is here. "The great Tower stands high over you." The souvenir model Eiffel Tower is here. "Comparatively tiny is the souvenir version." The great Eiffel Tower is fixed in place. Understand "actual" as the great Tower. Rule for printing the name of the great Tower while asking which do you mean: say "actual Tower". Rule for printing the name of the souvenir tower while asking which do you mean: say "souvenir". causes TAKE TOWER (for instance) to produce a nice tidy question in reply: "Which do you mean, the actual Tower or the souvenir?" 4. A note about actions. This activity takes place during the process of understanding the player's command, when the action that will take place is not fully known. So if the player types "TAKE SHOEBOX", this activity would happen when SHOEBOX is being examined for meaning. Inform knows that the action will be taking, but nothing else. That means attaching a proviso like "... while taking a container" to a rule for this activity will cause the rule to have no effect - whereas "... while taking" would be fine. Example 354 (*): Apples Prompting the player on how to disambiguate otherwise similar objects. Example 355 (*): Originals Allowing the player to create models of anything in the game world; parsing the name "model [thing]" or even just "[thing]" to refer to these newly-created models; asking "which do you mean, the model [thing] or the actual [thing]" when there is ambiguity. Example 356 (***): Walls and Noses Responding to "EXAMINE WALL" with "In which direction?", and to "EXAMINE NOSE" with "Whose nose do you mean, Frederica's, Betty's, Wilma's or your own?" 17.30. Supplying a missing noun/second noun 1. When it happens. (Two different activities here, but identical except for applying to different nouns.) Suppose that, because of an instruction to Understand something even though it would be lacking a noun - say, 'Understand "take" as taking.' - an incomplete action is generated, one which is required to have a noun, but doesn't. "Supplying a missing noun" takes place to remedy the problem. It can either: (i) Set a noun, printing text like "(presumably the black bag)" if it wants, in which case the action goes forward, though it is still subject to the full rules on accessibility exactly as any other action would be; or (ii) Make no choice, in which case no action takes place and the player's command is rejected. If the activity printed nothing, Inform will produce a generic reply to the player that "You must supply a noun.". 2. The default behaviour. In the default grammar for Inform, only three such half-finished actions are ever Understood. One is "going" with no direction, for which this activity simply prints a refusal. The other two are the two undirected senses, "smelling" and "listening". In each case, the "supplying a missing noun" activity sets the noun to the current location: so, for instance, typing the bare command "listen" might generate the action "listening to the Shoreline". 3. Examples. (a) This is the definition Inform uses to make "listen" work as outlined above: Rule for supplying a missing noun while listening (this is the ambient sound rule): now the noun is the location. (b) It can be elegant to allow second nouns to be dropped with habitual actions, or where the choice is obvious: Understand "unlock [something]" as unlocking it with. Rule for supplying a missing second noun while unlocking: if the skeleton key is carried, now the second noun is the skeleton key; otherwise say "You will have to specify what to unlock [the noun] with." Note that, in order for our activity to succeed, we do need to supply a grammar line allowing the player to try "unlocking it with" using only one noun. Otherwise, the command "unlock something" will still produce the question "What do you want to unlock the door with?" Example 357 (*): Latin Lessons Supplying missing nouns and second nouns for other characters besides the player. Example 358 (*): Minimal Movement Supplying a default direction for "go", so that "leave", "go", etc., are always interpreted as "out". 17.31. Reading a command 1. When it happens. When reading a command from the keyboard. 2. The default behaviour. Print the prompt text; wait for the player to type something and press return. Reject an entirely blank line, and treat a command beginning "oops" as a correction to the previous one. This is a fairly complicated business, so it is probably best not to change the "for" rules for this activity: "before", and especially "after", are another matter. (Note, however, that if Inform does reject a blank line and ask for another then this all happens inside the "for" rules: no "after" occurs after the blank line, nor does a "before" happen before the second attempt by the player. It is all a single round of the activity, not two.) 3. Examples. (a) To lead absolute beginners in gently: Before reading a command while the turn count is 1, say "(This is your chance to say what the protagonist should do next. After the '>', try typing 'take inventory'.)" (b) The following responds politely but firmly if the player tries to type "please look", say, instead of just "look": After reading a command: if the player's command includes "please": say "Please do not say please."; reject the player's command. To explain. Fragments of what the player has typed are called snippets: "the player's command" is the entire thing. We can test if a snippet matches a given pattern like so:

if (snippet) matches (topic):
This condition is true if the given snippet exactly matches the specification. Example: if the player's command matches "room [number]", ... will be true if the command is ROOM 101, but not if it's EXPLORE ROOM 7.

if (snippet) does not match (topic):
This condition is true if the given snippet does not exactly match the specification.

if (snippet) includes (topic):
This condition is true if the given snippet includes words matching the specification, either at the beginning, in the middle, or at the end. Example: if the player's command includes "room [number]", ... will be true if the command is ROOM 101, EXPLORE ROOM 7, or ROOM 22 AHOY, but not if it's VISIT ROOM GAMMA 7.

if (snippet) does not include (topic):
This condition is true if the given snippet does not include any run of words which matches the specification.
Lastly, we took drastic action with another new phrase:

reject the player's command
This phrase should be used only in rules for the "reading a command" activity. It tells Inform not to bother analysing the text further, but to go back to the keyboard. (No time passes; no turn elapses; nothing happens in the simulated world.)
(c) An improved version takes commands like "please drop the coin" and strips "please" from them, but then allows them to proceed normally: After reading a command: if the player's command includes "please": say "(Quelle politesse! But no need to say please.)"; cut the matched text. "Matched text" is a snippet containing the words which matched against the pattern in the most recent "includes" condition, so in this case it contains just the single word "please". Two phrases allow snippets to be altered:

replace (snippet) with (text)
This phrase should be used only in "after" rules for the "reading a command" activity; it replaces the snippet of command, usually the "matched text" found immediately before, with the given text. Example: if the player's command includes "room [number]": replace the matched text with "office".

cut (snippet)
This phrase should be used only in "after" rules for the "reading a command" activity; it replaces the snippet of command, usually the "matched text" found immediately before, with the given text. Example: if the player's command includes "or else": cut the matched text.
Note that "replace" and "cut" can only be used in "after reading a command" rules: not when an action has been chosen and has gone ahead into its rulebooks. Once the "reading a command" activity has finished, the command is final. (d) To make the word "grab" an abbreviation for "take all": After reading a command: if the player's command matches "grab", replace the player's command with "take all". ("Snippet" is actually a kind of value, so we could say "Ah, you typed '[the player's command]'!" or some such if we liked. But in practice only three snippets are likely to be useful: the two mentioned above, "player's command" and "matched text", and the "topic understood", used when matching the "[text]" token in command grammar.) (e) Finally, we can make still more detailed alterations to the text of the command using the techniques for indexed text presented in the Advanced Text chapter. For instance:

change the text of the player's command to (indexed text)
This phrase should be used only in "after" rules for the "reading a command" activity; it replaces the current command text entirely. Example: After reading a command: let T be indexed text; let T be the player's command; replace the regular expression "\p" in T with ""; change the text of the player's command to T. This converts the player's command to indexed text, which is then manipulated by searching for any punctuation mark and replacing it with blank text (that is, deleted), and then put back again as the new command.
Example 359 (**): Fragment of a Greek Tragedy Responding to the player's input based on keywords only, and overriding the original parser entirely. Example 360 (**): North by Northwest Creating additional compass directions between those that already exist (for instance, NNW) -- and dealing with an awkwardness that arises when the player tries to type "north-northwest". The example demonstrates a way around the nine-character limit on parsed words. Example 361 (**): Cloves Accepting adverbs anywhere in a command, registering what the player typed but then cutting them out before interpreting the command. Example 362 (***): Complimentary Peanuts A character who responds to keywords in the player's instructions and remarks, even if there are other words included. 17.32. Implicitly taking something 1. When it happens. When an action is tried which requires the actor (normally the player, of course) to be carrying something, but which is not in fact carried by that person. For instance, if the player types WEAR OVERCOAT in reference to a Moroccan overcoat currently draped over a chair. 2. The default behaviour. To print text such as "(first taking the Moroccan overcoat)" and then silently try taking the object in question (the overcoat). If the take succeeds, the silence means that nothing else is printed: if it fails, it will say why. No matter what rules are written for this activity, it is impossible to use it to allow the action to go ahead even without the item. The activity allows us to change how, or if, an implicit take will happen, but not to change the consequences of failure. (To do that, we would need a procedural rule to "ignore the carrying requirements rule", but this kind of unstitching of the action machinery needs to be done with caution.) 3. Examples. (a) Forbidding implicit takes for certain dangerous items. (This seems especially fair if taking such items might cause death: the player will not wish to be killed on the strength only of our guess as to what he might be intending to do.) Rule for implicitly taking the curare: say "Ordinarily you'd pick up the curare in order to be able to do that, but this seems like a good moment for caution." instead. (b) Changing the way the implicit action is reported for the player: Rule for implicitly taking something (called target): try silently taking the target; if the player carries the target, say "You appropriate [the target] first, of course. [run paragraph on]" (c) Combining implicit takes when the noun and second noun must both be carried: Rule for implicitly taking the noun when the second noun is a thing and the second noun is not carried by the player: try silently taking the noun; try silently taking the second noun; say "(first taking both [the noun] and [the second noun])[line break]" (d) Making another character reply amusingly: Rule for implicitly taking something which is carried by the player when the person asked is Clark: say "'I don't see how I'm supposed to do that when you're holding [the noun],' remarks Clark sulkily." instead. Example 363 (*): Pizza Prince Providing a pizza buffet from which the player can take as many pieces as he wants. Example 364 (*): The Big Sainsbury's Making implicit takes add a minute to the clock, just as though the player had typed TAKE THING explicitly. Example 365 (***): Lollipop Guild Overriding the rules to allow the player to eat something without first taking it. 17.33. Printing a parser error 1. When it happens. The parser is the part of the run-time software, included in all works produced by Inform, which tries to match the player's command against the grammar provided by the work. When it is unable to make a valid match, the parser prints an error to the player: for instance, > BIFURCATE TREE That's not a verb I recognise. There are some 19 possible messages. The one which the parser wants to say is stored in the variable "latest parser error", which has the convenient kind "command parser error". This has the following possible values: didn't understand error only understood as far as error didn't understand that number error can't see any such thing error said too little error aren't holding that error can't use multiple objects error can only use multiple objects error not sure what it refers to error excepted something not included error can only do that to something animate error not a verb I recognise error not something you need to refer to error can't see it at the moment error didn't understand the way that finished error not enough of those available error nothing to do error I beg your pardon error noun did not make sense in that context error 2. The default behaviour. Prints the message in question. 3. Examples. (a) Perhaps for newcomers: After printing a parser error: say "If you are new to interactive fiction, you may like to try typing HELP." (b) Or to give the parser a certain amount of character: Rule for printing a parser error when the latest parser error is the I beg your pardon error: say "What's that? Speak up, speak up." instead. Rule for printing a parser error: say "That's a rum thing to say, and no mistake." instead. Example 366 (*): WXPQ Creating a more sensible parser error than "that noun did not make sense in this context". Example 367 (***): Xot Storing an invalid command to be repeated as text later in the game. 17.34. Deciding whether all includes 1. When it happens. When parsing a command such as "take all", where the player uses "all" to signify everything within reach. 2. The default behaviour. The actual method used is complicated, as "all" is not as simple as it seems - "take all" would not include the player's own body, for instance, or the crescent moon. The point of this activity is to allow the normal method to be changed for given objects, or given kinds of object. 3. Examples. (a) Removing scenery from "all" (but see (4) below): Rule for deciding whether all includes scenery: it does not. The phrases "it does" and "it does not" make a decision. (b) Ensuring that a given thing, which might otherwise be excluded, is included: Rule for deciding whether all includes the oval roof: it does. 4. The Standard Rules already uses this. Note that the Standard Rules already stocks this activity with several rules: exclude scenery from take all rule exclude people from take all rule exclude fixed in place things from take all rule 5. A note about actions. This activity takes place during the process of understanding the player's command, when the action that will take place is not fully known. So if the player types "TAKE SHOEBOX", this activity would happen when SHOEBOX is being examined for meaning. Inform knows that the action will be taking, but nothing else. That means attaching a proviso like "... while taking a container" to a rule for this activity will cause the rule to have no effect - whereas "... while taking" would be fine. 17.35. Printing the banner text 1. When it happens. The banner is the bibliographic masthead text, which typically looks something like this: Relations An Interactive Fiction by Emily Short Release 1 / Serial number 050630 / Inform 7 build 2U98 (I6/v6.30 lib 6/10N) SD The banner is printed at the start of play, and when the player types "version" at the command line, and when say "[banner text]" occurs.

say "[the/-- banner text]"
This text substitution expands to the banner text giving bibliographic details of the current story file, rather like the opening credits of a movie, or the title page of a book.
2. The default behaviour. Prints the text above, giving the title, the headline, the author, the release number, the date of compilation (that's the serial number: YYMMDD), and version numbers of the Inform components used to put the game together. 3. Examples. (a) Adding a line to the banner: After printing the banner text, say "DRM authentication code: 13S-451-2034u75y65u%%a1248." (b) Simplifying the banner: Rule for printing the banner text: say "Welcome." instead. Example 368 (*): Bikini Atoll Delaying the banner for later. 17.36. Printing the player's obituary 1. When it happens. The obituary is the text "*** You have died ***" or similar, usually followed by the final score. 2. The default behaviour. Printing the aforementioned text, then the final score, and reducing the status line to a largely blank state. 3. Examples. (a) For a work with no meaningful score, it would be odd to wind up with a final reckoning of 0, so: Procedural rule: ignore the print final score rule. (b) Or we could add to the verdict: After printing the player's obituary: say "And you visited [number of visited rooms] place[s]." Example 369 (*): Battle of Ridgefield Completely replacing the endgame text and stopping the game without giving the player a chance to restart or restore. Example 370 (*): Finality Not mentioning UNDO in the final set of options. Example 371 (*): Jamaica 1688 Adding a feature to the final question after victory, so that the player can choose to reveal notes about items in the game. 17.37. Amusing a victorious player 1. When it happens. When the player chooses "AMUSING" from the short menu of choices after a game has been won. Traditionally, this is where the author gets to point out quirky by-ways of the game, or make some final acknowledgements, or simply salute the player's perseverance. Note that the AMUSING option is only offered when the story has ended finally, and that it is only offered if there is at least one rule present in the "for amusing a victorious player" rulebook. 2. The default behaviour. None. The "for amusing a victorious player" rulebook is empty by default, and no amusement is available. 3. Examples. The format would be like so: Rule for amusing a victorious player: say "Hmm. You're easily amused." Example 372 (**): Xerxes Offering the player a menu of things to read after winning the game. 17.38. Starting the virtual machine 1. When it happens. This activity is provided solely as a "hook" for any low-level tasks which need to be performed when the virtual computer which runs Inform story files is starting up. This happens much earlier than "when play begins" rules, and should be used only as a last resort. It should be remembered that Inform can produce story files for several different virtual computers. On some of these, it will not be safe to print any text during this activity, as the windows which would display such text do not yet exist. 2. The default behaviour. None. 3. Examples. No detailed examples will be given here, but the activity might be used (for instance) to set styles for the Glulx windows shortly to be brought into existence. Example 373 (*): Blankness Emptying the status line during the first screen of the game. 17.39. Review of Chapter 17: Activities 1. An activity is a process that can apply either to one thing or to nothing; every activity allows us to write "before...", "rule for...", and "after..." rules. In practice, new activities tend to be most useful when a. we are creating an extension or source that we expect other authors to use, and we want to provide an easy hook by which they can customize our output. b. we expect to write a lot of special cases to apply to a given situation, and we want the flexibility of rule definitions to describe these special cases. c. we want to define contexts within the game for use by other activities: for instance, we can write a rule such as Rule for printing the name of the spoon while asking which do you mean: say "enormous silver spoon" where the existence of the "asking which do you mean" activity makes it easy for us to tell Inform when to use this special name. 2. Creating new activities: Analysing something is an activity. Assaying is an activity. Analysing something is an activity. The analysing activity has a text called first impression. Before analysing: now the first impression is "unremarkable". Rule for analysing someone: now the first impression is "living tissue". After analysing something (called the sample): say "Your professional opinion of [the sample] is that it is [first impression]." Instead of examining something (called the sample): carry out the analysing activity with the sample. We can then invoke our created activities with phrases such as carry out the analysing activity with the pitchblende; carry out the assaying activity; 3. Because Inform's predefined activities are so numerous and specialized, we don't repeat all the examples here; it's worth looking back at individual sections to review what the specific activities can do. Printing and output Printing the name of something Printing the plural name of something Constructing the status line Listing contents of something Grouping together something Room descriptions Deciding the concealed possessions of something Writing a paragraph about Listing nondescript items of something Printing room description details of something Darkness Printing a refusal to act in the dark Printing the announcement of darkness Printing the name of a dark room Printing the description of a dark room Parsing Deciding the scope of something Clarifying the parser's choice of something Asking which do you mean Supplying a missing noun/second noun Reading a command Implicitly taking something Printing a parser error Deciding whether all includes Starting and ending the game Printing the banner text Printing the player's obituary Amusing a victorious player Starting the virtual machine Chapter 18: Rulebooks 18.1. On rules When we open the casing and look inside the machinery of Inform, what we see are rules and rulebooks. We seldom need to know how this machinery works, but every once in a while we want to replace components, or even install new mechanisms of our own. And as we shall see, creating new rulebooks can be a neat way to tackle complicated simulations full of exceptions and special cases. So far we have seen many rules, and the term "rulebook" has frequently but vaguely been used. Here is a summary of the rulebooks seen so far: before instead after check taking, carry out taking, report taking and three similar rulebooks for each of the 90 or so actions persuasion unsuccessful attempt reaching inside reaching outside visibility does the player mean when play begins when play ends every turn when Confrontation Scene begins when Confrontation Scene ends and two similar rulebooks for each scene we create, if any before printing the name of for printing the name of after printing the name of and three similar rulebooks for each of the 20 or so activities Which makes around 340 rulebooks before we even start to write - and one more is going to turn up later in this chapter: procedural All the same, not everything in Inform belongs to a rulebook - timed events, newly-created phrases, and definitions may look vaguely as if they define rules, but they do not, so the following are not rulebooks: At 11:10 PM: ... To dislodge the shelf: ... Definition: ... 18.2. Named rules and rulebooks Most of the rules built into Inform have names. For instance, a rule called "the advance time rule" is the one which increments the number of turns - usually visible on the "status line" displayed above the window of a game in progress - and advances the clock, which is usually not visible, but ticking away behind the scenes. A rulebook is a list of rules to be followed in sequence until one of them makes a decision. For instance, when actions get to the "instead" stage, each "instead" rule is tried until one of them chooses to do something. If the source text contains the rules Instead of taking something: say "You have no particular need just now." Instead of taking a fish: say "It's all slimy." and a command to TAKE something is tried, then only one of these rules will have any effect. The "instead" rulebook contains: Rule (1) to be applied if the action matches "taking a fish" Rule (2) to be applied if the action matches "taking something" Inside their rulebook, the rules are not listed in the order of definition in the source text. Rule (1) comes before rule (2) because it applies in more specific circumstances. This is the main idea: a rulebook gathers together rules about making some decision, or taking some action, and sorts them in order to give the more specific rules first choice about whether they want to intervene. Whereas only some rules are named (the two "instead" rules above have no name, for instance), every rulebook has a name. For convenience, the following forms of rule and rulebook name are synonymous: advance time = the advance time rule the instead rules = instead rulebook = instead The names of built-in rules have been chosen as descriptively as possible: the "can't go through closed doors rule", for instance. Names for rules tend to be verbose, but this is a situation where clarity is very much better than brevity. Example 374 (*): Nine AM Appointment A WAIT [number] MINUTES command which advances through an arbitrary number of turns. Example 375 (**): Delayed Gratification A WAIT UNTIL [time] command which advances until the game clock reaches the correct hour. 18.3. New rules Stretching a point seasonally, we might write: Every turn, say "The summer breeze shakes the apple-blossom." This rule is nameless. It needs no name because it will never need to be referred to: by identifying it as an every turn rule we have already said enough to lodge it in the "every turn" rulebook. In fact, though, it is easy to create a named rule: This is the blossom shaking rule: say "The summer breeze shakes the apple-blossom." The name of a rule must always end with the word "rule", for clarity's sake. (The phrasing "This is the ... rule" is used because "The ... rule" would be open to misinterpretation.) Previously we had a rule which had no name, but belonged to a rulebook: now we have the opposite, because although the "blossom shaking rule" has a name, it has not been placed in any rulebook. That means it will probably never be applied, unless we give specific instructions for that. Alternatively, it is possible to both name and place a rule in a single sentence: Every turn (this is the alternative blossom rule): say "The summer breeze shakes the apple-blossom." Now the "alternative blossom rule" is a named rule in the "every turn" rulebook. Example 376 (*): Stone A soup to which the player can add ingredients, which will have different effects when the player eats. Example 377 (*): The Crane's Leg 2 A description text generated based on the propensities of the player-character, following different rulebooks for different characters. Example 378 (**): Bribery A GIVE command that gets rid of Inform's default refusal message in favor of something a bit more sophisticated. 18.4. Listing rules explicitly If rules can manage perfectly well without, why bother to have names for rules? The answer is that although Inform contains an elaborate mechanism for placing rules into the correct rulebook at the correct position, and this happens automatically, Inform will sometimes get it wrong. It will use a rule we do not want, or place them in an order which does not suit us. To put this right, we can give explicit instructions which take precedence over Inform's normal practice. This is done with the "to list" verb, as in the following examples. 1. The simplest usage is to place a named rule, which currently has no home, in any rulebook of our choice. (This looks redundant, but just occasionally we want the same rule to appear in two different rulebooks.) The blossom rule is listed in the every turn rules. A rule can appear in more than one rulebook, but within any single rulebook it can only appear once. 2. We can also specify that the rule needs to appear before, or after, some other named rule in the same rulebook: The collapsing bridge rule is listed before the moving doorways rule in the instead rules. Instead of being placed in specificity order in the whole "instead" rulebook, the "collapsing bridge" rule would now be placed in specificity order only in the first half of the "instead" rulebook - the rules from the start up to (but not including) the "moving doorways" rule. "Listed" sentences are obeyed by Inform in sequence, so if later ones issue instructions contradicting earlier ones, it's the later ones which win out. Thus if we say "A is listed before B in X" and then "B is listed before A in X", the result is that B comes before A. 3. We can specify that a rule needs to appear first or last in a given rulebook: The collapsing bridge rule is listed first in the instead rules. Again, if we make several such instructions about the same rulebook then the most recent one wins: "A is listed first in X. B is listed first in X. C is listed first in X." causes rulebook X to begin C, B, A. 4. We can also substitute one rule for another: My darkness rule is listed instead of the can't act in the dark rule in the visibility rules. If rule A is listed instead of rule B in rulebook X, and A was already a rule in rulebook X, then A will move from its previous position to occupy the place where B was, and B will disappear. (In particular rule A will not be duplicated, which would break the principle that no rule occurs twice in the same rulebook.) 5. And we can strike down existing rules, either specifically or in all their applications: The can't act in the dark rule is not listed in the visibility rules. The can't remove from people rule is not listed in any rulebook. This does not actually destroy the rules in question: they could still, for instance, be put into another rulebook, or even be applied explicitly, as we shall see. But unless we take deliberate action to the contrary, un-listing a rule amounts to abolishing it forever. This is a little drastic, and we will see subtler ways to change the standard behaviour later in the chapter. Example 379 (*): Saint Eligius Adding a first look rule that comments on locations when we visit them for the first time, inserting text after objects are listed but before any "every turn" rules might occur. Example 380 (*): Verbosity 2 Making rooms give full descriptions each time we enter, even if we have visited before, and disallowing player use of BRIEF and SUPERBRIEF. Example 381 (**): Slouching A system of postures allowing the player and other characters to sit, stand, or lie down explicitly or implicitly on a variety of enterable supporters or containers, or in location. 18.5. Sorting and indexing of rules The Rules page of the index for a project offers a view of the rulebooks and their contents, with two major exceptions: built-in rules for specific actions are left to the Actions page, and any rules for scene endings or beginnings are left to the Scenes page. As we have seen, we need to know the name of a rule before we can change its rulebook listing or alter its applicability. The Rules and Actions index pages show the names of the built-in rules, which are not worth memorising. (Typing can be saved by selecting a rule's name, using Copy and then using Paste to insert the name into the source text.) In the Rules index, each rulebook is named (in italic type) and then followed by a list of the rules within it, one on each line: if nothing follows, then the rulebook is currently empty. The rules are given in order, and icons are used which indicate which rules are more specific than which others: for instance, a green-tipped arrow running downwards indicates that the rule below is more specific than the rule above. Hovering the mouse over such an icon should bring up a "tooltip" which explains Inform's reasoning: (Image rulesorting.png here) As this suggests, Inform performs its automatic sorting using a precise collection of Laws (the term "rules" would be ambiguous here, so we call these guidelines Laws instead), and the tooltip shows which Law was applied. It is bad style to write source text which absolutely depends on detailed points of these Laws, but they are documented at the end of this chapter for those who do wish to see the full details. 18.6. The preamble of a rule In general, a rule looks like this: preamble : list of one or more phrases divided by semicolons though in a few common cases (where the preamble begins with Before, After, Instead of, Every turn, or When, and there is only one phrase in the list) the colon can be replaced with a comma. Three kinds of declaration are special, and these we can tell apart by the first word: To ... - a new phrase: see the chapter on Phrases At ... - something due to happen at a given time: see Time Definition: ... - a new adjective: see Descriptions All other declarations (that is, starting with any other word) create rules fit for going into rulebooks. The preamble can either just be a name, which is required to end with the word "rule", or it can give circumstances and have no name, or it can do both: This is the ...name of rule... ...circumstances... ...circumstances... (this is the ...name of rule...) The circumstances should be a sequence of the following ingredients, each of which is optional except the name of the rulebook: first or last followed by ...rulebook name... followed by about or for or of or on or rule followed by ...what to apply to... followed by while or when ...condition... followed by during ...a scene... The word "first" or "last", if present, is significant: it tells Inform exactly where the new rule should be placed into its rulebook, and so overrides the normal practice of placing the rule according to how specific it is. On the other hand, the use of any of the words "about", "for", etc., is purely to make the grammar easier to follow for: Inform does not make any direct use of these words (except perhaps that it may help to avoid ambiguities by separating the rulebook name from what is being applied to). Thus in the rule Instead of kissing Clark: ... the word "instead" is the rulebook's name, while "of" is technically optional. "Instead about kissing Clark: ..." would work just as well, but would make the source text harder to read. In this whole list of possible ingredients, only the rulebook name is compulsory. We could define a rule called simply "Instead: ..." if we wanted - though its universal applicability would make it pretty disruptive, with every action stopped in its tracks. Example 382 (*): We Replacing the standard action report rules to reflect our own design. Example 383 (***): Backus-Naur form for rules The full grammar Inform uses to parse rule definitions, in a standard computer-science notation. 18.7. New rulebooks Creating a new rulebook is also straightforward, as we see in the following modest example game: "Appraisal" The Passage is east of the Tomb. The green-eyed idol is in the Tomb. A Speak-Your-Progress machine is in the Passage. Appraisal rules is a rulebook. An appraisal rule: say "Click... whirr... the score is [the score in words] points." An appraisal rule: if we have taken the idol, say "Most importantly of all, the idol has been found." Instead of switching on the machine, follow the appraisal rules. The creation of the rulebook is all very well, but without the final sentence it would never be used. The crucial new phrase here is:

follow (rule)
This phrase causes the rule to be obeyed immediately (rather than simply at predetermined times such as when a particular action is being tried, or at the end of every turn, and such). Example: follow the advance time rule; follow the appraisal rulebook;
Like "number" or "text", "rule" and "rulebook" are kinds of value built into Inform: "the blossom rule" is a value whose kind is "rule", whereas "the every turn rules" is a value whose kind is "rulebook". In fact, Inform considers a rulebook to be a special case of a rule, so that whenever a rule is required it is legal to name a rulebook instead, but not vice versa. The "follow" phrase here... Instead of switching on the machine, follow the appraisal rules. ...expects to be applied to a value of kind "rule"; "the appraisal rules" is in fact a rulebook, but since that counts as a rule the phrase makes sense to Inform. To follow a rulebook means to run through all its rules in turn, stopping when one rule reaches an outcome; to follow a single rule means just that one, of course. When created, a rulebook starts out with no rules in it - in this example, of course, we quickly defined a couple of rules to go into it. But it's often the case in Inform that a rulebook exists without ever being stocked up, especially if the rulebook is for some obscure purpose never needed. The built-in adjectives "empty" and "non-empty", applied to a rulebook, test whether any rule is present or not. Example 384 (***): In Fire or in Flood A BURN command; flammable objects which light other items in their vicinity and can burn for different periods of time; the possibility of having parts or contents of a flaming item which survive being burnt. 18.8. Basis of a rulebook Every rulebook works on a value supplied to it, though it doesn't always look that way. The kind of the value is called its "basis"; for example, if a rulebook works on a number, it's called a "number based rulebook". Most of the rulebooks seen up to now have been action based rulebooks: Instead of eating the cake: ... "Instead" is an action based rulebook, and the action it works on is the one currently being processed. Besides before, after and instead, other action based rulebooks include the check, carry out, and report rules; general rulebooks such as every turn rules, the procedural rules, the visibility rules, the turn sequence rules; and rules specially for dealing with the actions of other characters, such as the persuasion and unsuccessful attempt rules. But we have also seen object based rulebooks: Rule for reaching inside the flask: ... "Reaching inside" is an object based rulebook, and here we're giving it a rule which applies if the object is the flask. Inform would reject something like: Rule for reaching inside 100: ... because 100 has the wrong kind to fit - it's a number, not an object. There are many object based rulebooks, because most activities built-in to Inform act on objects. For example, the "printing the name of" activity has three rulebooks attached to it: before printing the name of, for printing the name of, after printing the name of. All of these are object based rulebooks. Finally, we've also seen scene based rulebooks (which is how rules like "when a recurring scene ends" worked, in the Scenes chapter). If a rulebook is declared like so: Marvellous reasoning is a rulebook. then it is an action based rulebook. If we want something different, we must write something like this: Grading is a number based rulebook. Grading 5: say "It's five. What can I say?" instead. Grading an odd number (called N): say "There's something odd about [N]." instead. Grading a number (called N): say "Just [N]." instead. When play begins: repeat with N running from 1 to 10: say "Grading [N]: "; follow the grading rulebook for N. which produces: Grading 1: There's something odd about 1. Grading 2: Just 2. Grading 3: There's something odd about 3. Grading 4: Just 4. Grading 5: It's five. What can I say? Grading 6: Just 6. Grading 7: There's something odd about 7. Grading 8: Just 8. Grading 9: There's something odd about 9. Grading 10: Just 10. Here we needed a variation on "follow" which supplies the value to apply to:

follow (values based rule producing values) for (value)
This phrase causes the rule to be obeyed immediately (rather than simply at predetermined times such as when a particular action is being tried, or at the end of every turn, and such), and applies it to the value given, which must be of a matching kind. Example: follow the reaching inside rulebook for the electrified cage;
And here is an example based on objects: The flotation rules are an object based rulebook. A flotation rule for the cork: rule succeeds. A flotation rule for an inflated thing: rule succeeds. A flotation rule: rule fails. And we might use the flotation rules in a circumstance like this: After inserting something into the well: follow the flotation rules for the noun; if the rule succeeded: say "[The noun] bobs on the surface."; otherwise: remove the noun from play; say "[The noun] sinks out of sight." Example 385 (*): Flotation Objects that can sink or float in a well, depending on their own properties and the state of the surrounding environment. 18.9. Rulebook variables When a rulebook is intended to perform some complicated task or calculation, it is sometimes useful for earlier rules to be able to leave information which will help later ones. For instance, suppose we want a rulebook which is intended to print out the player's current aptitude. We will suppose that this is a number from 0 upwards: the higher, the apter. The player gets bonus aptitude marks for achievements, but marks deducted for accidents, and so on. Moreover, we want to design this system so that it's easy to add further rules. The natural solution is to have a number which varies (or 'variable') acting as the running aptitude total: it should start at 0 and be altered up or down by subsequent rules. First, we should make the rulebook, and then add a variable: Aptitude is a rulebook. The aptitude rulebook has a number called the aptitude mark. The new value 'aptitude mark' is shared by the rules of the rulebook: nobody else can see it. It is created at the start of the rulebook being followed, and destroyed at the end. (If the rulebook should be followed a second time inside of itself, a new copy is created which does not disturb the old one.) So, in this case, 'aptitude mark' is started as 0 (since it is a number) each time the aptitude rules run. We can then write whatever rules we please to modify it: An aptitude rule: if in darkness: decrease the aptitude mark by 3. An aptitude rule: if we have taken the idol: increase the aptitude mark by 10. And we had better do something with the result: The last aptitude rule: say "Your aptitude rating is [aptitude mark]." A rulebook can have any number of variables like this. They behave much like "let" values except that they last for a whole rulebook, not an individual rule or To phrase definition. (Well, strictly speaking they are accessible not just to the rules which belong to the rulebook, but also to any rules which previously belonged to the rulebook but were kicked out by means of an explicit rule-listing sentence. This is good because otherwise they will suddenly cause problem messages when unlisted.) 18.10. Success and failure Though we have blurred over this point so far, each rule must ordinarily end with one of three outcomes: success, failure and neither ("no outcome"). When a rulebook is followed, what happens is that each of its rules is followed in turn until one of them ends in success or failure - if ever: it is possible that each rule is tried and each ends with no outcome, so that the rulebook simply runs out of rules to try. For some rulebooks, these are not useful ideas: "every turn" rules, for instance, never produce an outcome, which is why the "every turn" rulebook always runs through all its rules at the end of each turn. But for other rulebooks, such as "check taking", it's important that a rule which fails will stop the whole rulebook. For instance, we might find that the "can't take yourself rule" produces no outcome (because we aren't trying to do that), and then likewise the "can't take other people rule" (ditto) but that the "can't take component parts rule" prints up a complaint, and fails the action: the rulebook stops, and never goes on to (for instance) the "can't take scenery rule". This is good, because an impossible action often fails for several reasons at once, and we only want to print up one objection, not a whole list. To follow the working of this mechanism, we need to be able to predict the outcome of any given rule. Sometimes this is easy to spot. For instance, in a rule which works on actions: continue the action; means "end this rule with no outcome" stop the action; means "end this rule in failure" ... instead; means "end this rule in failure" ("Success" and "failure" are technical terms here: they do not mean that the player has or hasn't got what he wanted.) This is why the rule: Before taking something: say "The sentry won't let you!" instead. ends in failure, and therefore stops the "before" rulebook. Another easy-to-spot case is when a rule makes use of the explicit phrases:

rule succeeds
This causes the current rule to end immediately, with its outcome considered to be a success. That means the rulebook being worked through will also end, and also be a success.

rule fails
This causes the current rule to end immediately, with its outcome considered to be a failure. That means the rulebook being worked through will also end, and also be a failure.

make no decision
This causes the current rule to end immediately, but with no outcome. That means the rulebook being worked through will continue to run on, beginning with the next rule.
But what happens if a rule simply doesn't say whether it succeeds, fails or has no outcome? In that case it depends on the rulebook. For almost all rulebooks, a rule which doesn't make a choice has no outcome, as in the following example: Before taking something: say "The sentry looks at you anxiously!" This rule, if it takes effect, ends with no outcome - so the action continues. But other rulebooks have a different convention: the most important is "instead", where a rule making no explicit choice is deemed to end in failure. For instance: Instead of taking something: say "The sentry prods you with his rifle!" This rule, if it takes effect, ends in failure and therefore stops the action. We call this the default outcome of a rulebook. The default outcome of "before" (and of almost all rulebooks, in fact) is no outcome; the default outcome of "instead" is failure; the default outcome of "after" is success. The few exceptional cases with default outcome success or failure are marked as such in the Rules index. When we create a rulebook, it will default to "no outcome". But we can specify otherwise with sentences like so: The cosmic analysis rules are a rulebook. The cosmic analysis rules have default failure. Finally, note that the default outcome for a rulebook is really the default outcome for any rule in that rulebook: if no rules in the rulebook ever apply, for instance if there aren't any and the rulebook is empty, then the rulebook ends with no outcome at all. We can test the latest outcome like so:

if rule succeeded:
This condition is true if the most recently followed rule ended in success. Example: follow the hypothetical clever rule; if rule succeeded: ...

if rule failed:
This condition is true if the most recently followed rule ended in failure. Example: follow the hypothetical clever rule; if rule failed: ... Note that this is not the opposite of "rule succeeded", because there's a third possibility: that it ended with no outcome.
Example 386 (*): Feline Behavior A cat which reacts to whatever items it has handy, returning the result of a rulebook for further processing. Example 387 (**): Kyoto Expanding the effects of the THROW something AT something command so that objects do make contact with one another. 18.11. Named outcomes We have seen that the terms "success" and "failure" can be misleading - after all, it might be a good thing for a particular rulebook to "fail". At any rate, these are vague terms, and we don't want to have to remember the conventions used by every rulebook. This is why certain rulebooks have explicitly named outcomes instead. For instance, the "visibility" rules are allowed to have the outcomes: there is sufficient light; there is insufficient light; These look like phrases, but are in fact named outcomes which can only be used in visibility rules. (They would make no sense elsewhere, and Inform will not allow their use if they are clearly out of context.) Such named outcomes are listed in the Rules index. There can be any number of named outcomes. For instance, the Standard Rules define: The does the player mean rules are a rulebook. The does the player mean rules have outcomes it is very likely, it is likely, it is possible, it is unlikely and it is very unlikely. which makes five possible outcomes. Five outcomes seems to contradict the principle that there are only three possible outcomes for a rule: in fact, though, the five are counted as five different forms of "success", and any of them will cause a "does the player mean" rule to succeed. If we do not want this, we can instead specify explicitly how the named outcomes correspond to success, failure or "no outcome": Visibility rules have outcomes there is sufficient light (failure) and there is insufficient light (success). Again, see the Rules index for examples. The same named outcome can be used for more than one rulebook, and can have different meanings in the context of different rulebooks - "good news" could be defined as success in one rulebook and failure in another, for instance. (This means that rulebook creators need not worry about name clashes and is an important difference in behaviour between rulebook outcomes and kinds of value.) We can even name a specific named outcome as the default outcome for rules in this rulebook: Audibility rules have outcomes high background noise (failure), low background noise (success - the default) and absolute silence (success). After a rulebook using named outcomes has run, we can test which outcome occurred by using the phrase:

outcome of the rulebook ... rulebook outcome
This phrase produces the (named) outcome of the phrase most recently followed. Example: follow the audibility rules; if the outcome of the rulebook is the absolute silence outcome: say "You could hear a pin drop in here."
Each named outcome is a value if followed by the word "outcome", which is how "absolute silence" has become "the absolute silence outcome". Named outcomes can be said, so we could use the text substitution "[outcome of the rulebook]", for instance. A final caveat: it is perfectly legal to create a named outcome which means "no outcome", but if so then this will never be "the outcome of the rulebook" because "no outcome" is not an outcome. Example 388 (*): Being Peter A set of rules determining the attitude a character will take when asked about certain topics. 18.12. Rulebooks producing values We have now seen two ways to write the outcome of a rule: as simple success or failure, with more or less explicit phrases like: rule succeeds; rule fails; continue the action; stop the action; and by using a named outcome for the current rulebook as if it were a phrase, as in: low background noise; There is still a third way: we can stop a rule and at the same time produce a value. This isn't needed very often - none of the built-in rulebooks in the Standard Rules produces a value. As we've seen, every rulebook has one kind of value as its basis, and it also has another kind of value for it to produce. If we call these K and L, then we have altogether four ways to write down the kind of a rulebook: rulebook K based rulebook rulebook producing L K based rulebook producing L If we don't mention K, Inform assumes the rulebook is action based. If we don't mention L, Inform assumes L is "nothing", that is, Inform assumes no value is ever produced. Thus Drum summons rules is a rulebook. is equivalent to Drum summons rules is an action based rulebook producing nothing. But let's now look at a rulebook which does produce something. The cat behavior rules is a rulebook producing an object. This rulebook works out which thing the cat will destroy next. We might have rules like this one: Cat behavior when Austin can see the ball of wool: rule succeeds with result the ball of wool. The value is produced only when a rule succeeds, using this phrase:

rule succeeds with result (value)
This phrase can only be used in a rule which produces a value, and the value given must be of the right kind. It causes the current rule to finish immediately, to succeed, and to produce the value given.
How are we to use the cat behavior rulebook? If we write: consider cat behavior then the rulebook runs just as any other rulebook would, but the value produced is lost at the end, which defeats the point. Instead, we might write: Every turn: let the destroyed object be the object produced by the cat behavior rules; if the destroyed object is not nothing: say "Austin pounces on [the destroyed object] in a flurry."; remove the destroyed object. The key phrase here is object produced by the cat behavior rules which accesses the value this rulebook produces. In general, we write:

(name of kind) produced by (rule producing values) ... value
This phrase is used to follow the named rule, and to collect the resulting value.

(name of kind) produced by (values based rule producing values) for (value) ... value
This phrase is used to follow the named rule based on the value given, and to collect the resulting value.
Example 389 (***): Tilt 2 A deck of cards with fully implemented individual cards; when the player has a full poker hand, the inventory listing describes the resulting hand accordingly. 18.13. Consider and abide It often happens that one rule needs to invoke another one. The best way to do this is with the phrase:

consider (rule)
This phrase applies the given rule, but throws away the result: indeed, it makes no difference whether the rule succeeds, fails or has no outcome.

consider (values based rule producing values) for (value)
This phrase applies the given rule, applying it to the given value, but throws away the result: indeed, it makes no difference whether the rule succeeds, fails or has no outcome.
More often, though, we want not only to invoke another rule, but also to be guided by its advice. For this, we use the otherwise identical phrase:

abide by (rule)
This phrase applies the given rule, and makes its result the result of the present rule. If the rule being abided by succeeds or fails then the original rule also stops, at once and without going on to any further instructions. Example: The omnibus rule: abide by the first rule; abide by the second rule; abide by the third rule; abide by the fourth rule. This duplicates the effect of a rulebook of four rules: the "omnibus rule" tries each in turn, and stops as soon as any of them stop.

abide by (values based rule producing values) for (value)
This phrase applies the given rule to the given value, and makes its result the result of the present rule. If the rule being abided by succeeds or fails then the original rule also stops, at once and without going on to any further instructions.
Abide might be used in examples like this one: A thing can be fragile or robust. This is the can't handle fragile things roughly rule: if the noun is fragile, say "[The noun] is too fragile for such rough handling." instead. A check dropping rule: abide by the can't handle fragile things roughly rule. A check throwing it at rule: abide by the can't handle fragile things roughly rule. Had we used "consider" instead of "abide by", then in the event of the player typing "drop angel" the text "The glass angel is too fragile for such rough handling" would be printed, which is correct - but then the action would continue as though no difficulty had occurred, which is definitely not correct. Finally, we can "anonymously abide":

anonymously abide by (rule)
or: anonymously abide by (values based rule producing values) for (value)
This phrase applies the given rule, and makes its result the result of the present rule. If the rule being abided by succeeds or fails then the original rule also stops, at once and without going on to any further instructions. However, the rule deemed to have decided the outcome is the one abided by, not the one doing the abiding.
This is only useful in complicated situations where one rulebook uses another which... and so on. Its effect is exactly the same as "abide", except that the rule deemed to have decided the outcome is the one abided by, not the one doing the abiding. It thus allows a rule or rulebook to act purely as a middle-man, never getting the blame or the credit for what happens. The rule which made the decision is often not very relevant anyway, but it's used as the source of the value "reason the action failed" (see the Advanced Actions chapter). 18.14. Procedural rules (Beta release note) This section and the next are about a feature which is being withdrawn from Inform in future. Experience shows there are equally good ways to achieve the same ends without needing procedural rules. As elegant as they were, they often confused users, and they were expensive at run-time (that is, they made everything work more slowly). Withdrawing them from Inform will make it possible to make more efficient story files, and will simplify the language. Before any rule or rulebook is followed, a special rulebook is always consulted first. This is called the "procedural rules", and it starts out empty: so if we write no procedural rules, empty it will remain. Like the points of order which precede a debate, the procedural rules are not intended to contribute to any decision in themselves, but merely to sort out which voices are to be heard when the time for decision comes. Should some rules be waived, or others substituted? Should the rulebook be rearranged, in certain circumstances? And so on. Procedural rules offer enormous flexibility and with them one could deconstruct Inform and put it back together in a very different shape - but in practical situations they will only occasionally be needed. Procedural rules are not allowed to say anything, or indeed to do anything which might have practical consequences; they are only allowed to think about the current situation (if they need to) and then use special phrases (if they choose to) which affect how other rules are to be followed. For instance: A procedural rule: if the player is in the Timeless Void, ignore the advance time rule. Since the "advance time rule" is the one which moves on the number of turns and the clock, this means that the Timeless Void lives up to its name. Example 390 (*): Access All Areas The Pointy Hat of Liminal Transgression allows its wearer to walk clean through closed doors. 18.15. Phrases concerning rules (Beta release note) This section and the previous one are about a feature which is being withdrawn from Inform in future. Experience shows there are equally good ways to achieve the same ends without needing procedural rules. As elegant as they were, they often confused users, and they were expensive at run-time (that is, they made everything work more slowly). Withdrawing them from Inform will make it possible to make more efficient story files, and will simplify the language. The "ignore" phrase is only one of a suite, which should only be used in procedural rules. The full list is:

ignore (rule)
This phrase can only be used in procedural rules, which are now deprecated. It causes the named rule to be ignored (skipped over without producing a result) within the scope of the current "follow".

reinstate (rule)
This phrase can only be used in procedural rules, which are now deprecated. Its only effect is to reverse the effect of any "ignore" phrase affecting the rule named.

reject the result of (rule)
This phrase can only be used in procedural rules, which are now deprecated. It causes the named rule to used, but to have its result ignored, within the scope of the current "follow". In other words, if the rule succeeds or fails then this is suppressed and its rulebook continues.

accept the result of (rule)
This phrase can only be used in procedural rules, which are now deprecated. Its only effect is to reverse the effect of any "reject the result of" phrase affecting the rule named.

substitute (rule) for (rule)
This phrase can only be used in procedural rules, which are now deprecated. Whenever the second rule is to be invoked - from any rulebook, or as a result of any "follow" instruction - invoke the first one instead.

restore the original (rule)
This phrase can only be used in procedural rules, which are now deprecated. Its only effect is to reverse the effect of any "substitute ... for ..." phrase affecting the rule named.

move (rule) to before (rule)
This phrase can only be used in procedural rules, which are now deprecated. This causes the first rule to be ignored whenever it turns up in the ordinary way, but to be invoked either immediately before the second rule whenever that second rule is invoked. In effect, it cuts out the first rule from wherever it was, and glues it onto the second. Note that there is no obligation for the first rule to begin in the same rulebook(s) as the second, so this can be used to slot in a wholly new rule, perhaps only if certain circumstances hold.

move (rule) to after (rule)
This phrase can only be used in procedural rules, which are now deprecated. This causes the first rule to be ignored whenever it turns up in the ordinary way, but to be invoked either immediately after the second rule whenever that second rule is invoked. In effect, it cuts out the first rule from wherever it was, and glues it onto the second. Note that there is no obligation for the first rule to begin in the same rulebook(s) as the second, so this can be used to slot in a wholly new rule, perhaps only if certain circumstances hold.
These rule-changing instructions allow apparently casual sentences to wreak havoc with the model world. This, for instance, is quite the recipe for mayhem and perplexity: A procedural rule: reject the result of the before rules; ignore the after rules; move the after rules to before the before rules. Example 391 (*): Uptempo Adjust time advancement so the game clock moves fifteen minutes each turn. Example 392 (**): Lethal Concentration 1 A poisonous gas that spreads from room to room, incapacitating or killing the player when it reaches sufficient levels. Example 393 (**): Swigmore U. Adding a new kind of supporter called a perch, where everything dropped lands on the floor. Example 394 (**): Solitude Novice mode that prefaces every prompt with a list of possible commands the player could try, and highlights every important word used, to alert players to interactive items in the scenery. Example 395 (***): Lethal Concentration 2 Poisonous gas again, only this time it sinks. 18.16. Consider is not the same as follow (Beta release note) As part of the simplification involved in removing procedural rules from Inform, "consider" will, in fact, mean exactly the same as "follow". So the following text will be redundant. "Consider" looks as if it duplicates the effect of "follow", but in fact it is a simpler business altogether. Unlike "follow", it doesn't get side-tracked into consulting the procedural rules, with all of the resultant change which might result from that. This is a finicky but important distinction. A great many rules and rulebooks make use of each other when actions are being processed, but we only want the procedural rules to be looked at once, right at the start. A general guideline here is that if rule A needs to use rule B, and both are engaged in the same basic activity - for instance both are basically processing actions - then A should use "consider B". Only if B is something entirely unrelated should A use "follow B". Thus: Instead of switching on the machine, follow the appraisal rules. ...is a case where rule A, the one about processing the "switch on the machine" action, is engaged in a completely different activity to rule B, which is all about telling the player what a wonderful amount of progress has been made so far. "Follow" is therefore appropriate. Example 396 (****): Patient Zero People who wander around the map performing various errands, and in the process spread a disease which only the player can eradicate. 18.17. Two rulebooks used internally Rulebooks handle almost all of the important tasks which an Inform work of IF must carry out in order to keep play going. We have seen them used in clarifying the player's command, supplying missing ingredients, processing the action to see what should happen, responding, and so on: by this point in the documentation, it must look as if Inform uses rulebooks for everything. This is nearly true. There is not actually a super-rulebook controlling everything. (Such a super-rulebook would need to repeat itself and never finish, something a rulebook is not allowed to do.) Instead, what happens during play looks like so: 1. Following the "when play begins" rulebook. 2. Repeating: 2(a). Reading and parsing a command into an action; 2(b). Following the "action processing" rulebook; 2(c). Following the "turn sequence" rulebook. until the game has finished. 3. Following the "when play ends" rulebook. The command parser occasionally calls on the services of activity rulebooks to help it, but otherwise gets on with its job in ways that we do not "see" as Inform 7 users. The rest of what happens involves rulebooks, and in particular two important beneath-the-surface rulebooks: action processing and the turn sequence. The action processing rules are used whenever an action must be tried, by whoever tries it. This usually happens in response to player commands, but not always: it might happen because of a "try...", and it can certainly interrupt an existing action. The turn sequence rules are used at the end of each turn, and include housekeeping as well as timekeeping. They consult the "every turn" rulebook, and advance the time of day, among other useful tasks. In general, we should only modify the operation of these two crucial rulebooks as a last resort. Play can evidently fall to pieces if they cease to work normally. Example 397 (*): Electrified Adding a rule before the basic accessibility rule that will prevent the player from touching electrified objects under the wrong circumstances. Example 398 (*): Timeless A set of actions which do not take any game time at all. Example 399 (**): Endurance Giving different actions a range of durations using a time allotment rulebook. Example 400 (**): Escape from the Seraglio Replacing the usual response to TAKE ALL so that instead of output such as "grapes: Taken. orange: Taken.", Inform produces variable responses in place of "grapes:". 18.18. The Laws for Sorting Rulebooks Large works created by Inform are heaped high with rules, most of them instead rules, but with a leavening of befores and afters as well. What will happen if these conflict with each other? For instance: Instead of opening a container, say "Your mother-in-law looks on with such evident disappointment that you withdraw your hand again." Instead of opening an open container, say "Your daughter tuts in theatrical exasperation at your, like, lameness." Such clashes are resolved by sorting the rulebooks in order of specificity: thus your daughter gets in before your mother-in-law, because although both have rules hanging on the "opening" action, "an open container" is more specific than "a container". The full set of Laws used by Inform to sort rulebooks is quite elaborate. As we've seen, practical consequences can be investigated using the Rules index; and in most cases, the results are either natural (as above) or irrelevant (because the two rules being compared could not both activate at the same time anyway); but the full set of Laws is laid out below, for reference. It is probably a bad idea to write source text which absolutely relies on non-obvious rule sorting conventions, just the same, because this will make the source text harder to read and understand. Sorting is done by comparing rules in pairs to decide which is more specific. We shall call these rules X and Y. The Laws are tried in sequence; the first Law to distinguish X and Y gets to decide which is more specific. If no Law is able to decide, X and Y go into the rulebook in order of their appearance in the source text - that is, whichever is defined first appears earlier in the rulebook and therefore takes priority. Law I - Number of aspects constrained. For action-based rulebooks, rules are scored from 0 to 6 according to whether they constrain any of: (i) the exotic "going" clauses (pushing, by and through), (ii) the location of the action (in, from and to), (iii) the things directly involved (actor, noun, second noun, "nowhere" in the case of "going"), (iv) the presence of others (in the presence of...), (v) the time at which the action occurs (when, or "for the nth time" or "for the nth turn"), and/or (vi) the scene the action occurs in (during). For value based rulebooks, rules are scored from 0 to 3 according to whether they constrain: (i) the value parameter, (ii) the scene in which the rulebook is followed (when, during), and/or (iii) any condition which must hold or activities going on at the same time (when/while). A higher score is more specific than a lower one. Law II - When/while requirement. A rule with a when/while restriction beats one without. Law III - Action requirement. A rule with a more specific action requirement beats one with a more general action requirement. (Or similarly, for value based rulebooks, a rule with a more specific parameter requirement beats a more general one.) Details are given below. Law IV - Scene requirement. A rule with a scene restriction ("during") beats one without. Details of Law III now follow: Law III.1 - Object To Which Rule Applies. For value based rulebooks only: the more specific value requirement wins. Law III.2.1 - Action/Where/Going In Exotic Ways. A more specific combination of "...pushing...", "... by ...", and "... through ..." clauses in a "going" action beats a less specific. (Placing conditions on all three of these clauses beats placing conditions on any two, which beats any one, which beats none at all.) In cases where X and Y each place, let's say, two such conditions, they are considered in the order "...pushing...", "...by..." and then "...through..." until one wins. (The idea here is that pushing something from room to room is rarer than travelling in a vehicle, which in turn is rarer than going through a door. The rarer action goes first, as more specific.) Law III.2.2 - Action/Where/Room Where Action Takes Place. A more specific combination of conditions on the room in which the action starts, and in which it ends, beats a less specific. For all actions other than "going", there is no combination to be considered, and what we do is to look at the specificity of the "... in ..." clause. (So "Before looking in the Taj Mahal" beats "Before looking".) For "going" actions, there are strictly speaking three possible room clauses: "... in ...", "... from ..." and "... to ...". However, "... in ..." and "... from ..." cannot both be present, so that in practice a "going" rule constraining two rooms beats a "going" rule constraining only one. If both the room gone from (the "...in..." or "...from..." room, whichever is given) and the room gone to (the "... to..." room) are constrained, then the constraints are looked at in the order from-room followed by to-room, since an action which goes to room Z could start in many different places and thus is likely to be more general. Giving a place as a specific room beats giving only the name of a region; if region R is entirely within region S, then a rule applying in R beats a rule applying in S. (Note that regions can only overlap if one is contained in the other, so this does not lead to ambiguity.) Law III.2.3 - Action/Where/In The Presence Of. A more specific "...in the presence of..." clause beats a less specific one. (This is again a constraint on where the action can take place, but it's now a potentially a constraint which could be passed in many different places at different times, so it's the most likely to be achieved and therefore the last to be considered of the Laws on Where.) Law III.3.1 - Action/What/Second Thing Acted On. A more specific constraint on the second noun beats a less specific. Thus "putting something in the wooden box" beats "putting something in a container". Law III.3.2 - Action/What/Thing Acted On. A more specific constraint on the first noun beats a less specific. Thus "taking a container which is on a supporter" beats "taking a container". In the case of "going" actions, the first noun is a direction. The special constraint "going nowhere" (which means: a direction in which the actor's location has no map connection) is considered more general than any other constraint placed on the first noun, but more specific than having no constraint at all. Thus "Instead of going north" beats "Instead of going nowhere" which beats "Instead of going". Law III.3.3 - Action/What/Actor Performing Action. A more specific constraint on the actor beats a less specific. Law III.4.1 - Action/How/What Happens. A more specific set of actions beats a less specific. For instance, "taking" beats "taking or dropping" beats "doing something other than looking" beats "doing something". A named kind of action (such as "behaving badly") is more specific than "doing something", but considered less specific than any explicitly spelled out list of actions. Law III.5.1 - Action/When/Duration. An action with a constraint on its history ("for the fifth time", say, or "for the fifth turn") beats one without. If both rules place constraints on history, then the one occurring on the smaller number of possible turns wins (thus "for the third to seventh time" - 5 possible turns of applicability - beats "for less than the tenth turn" - 9 possible turns). Law III.5.2 - Action/When/Circumstances. A more specific condition under "...when..." beats a less specific one. These conditions could potentially be complex: Inform judges how specific they are by counting the clauses found in them. The more clauses, the more specific the condition, it is assumed. Law III.6.1 - Action/Name/Is This Named. A rule with a name ("the apple blossom rule", say) beats a rule without. 18.19. Review of Chapter 18: Rulebooks 1. When a work of IF by Inform is playing, rules are being followed: one after another, in lists followed in sequence. A rule is sometimes like a rule of a game, for instance stopping someone from crossing a bridge when it is guarded by a troll: but rules also govern presentational points, the enforcement of physical realism, the way the player's commands are understood and so on. A minimal game produced by Inform contains about 650 rules: for comparison, the large example "The Reliques of Tolti-Aph" has 1176. The list of rules in a game, including those pre-defined by Inform, may be found from the Rules Index. 2. A rulebook is a sequence of rules to be followed in order until one of them stops the process by making a decision (as a success or a failure, possibly accompanied by a value of some kind). In theory, there is no reason why we could not put the whole decision-making contents of a given rulebook into a single large rule, but breaking out complex decisions into a number of separate rules makes it easier for later authors to modify parts of the behavior at will. Each rulebook aims to achieve some single, clearly-defined task: sometimes to change matters, sometimes to decide on a particular value, but other times simply to validate something - for instance, that a given command can be applied sensibly to a given noun. A rulebook has to be based on a given kind, or else on "action", which isn't technically a kind but behaves like one for this purpose. The following are equivalent: The visibility rules are a rulebook. The visibility rules are an action based rulebook. Other bases are possible Grading is a number based rulebook. The flotation rules are an object based rulebook. Action based rules refer to the action most recently taken by the player, as in Before attacking something: ... A persuasion rule for asking someone to try jumping: ... 3. Some rules have names, such as Inform's built-in "can't reach inside closed containers rule". Others, like the ones defined by the following, do not: Before attacking the dog: ... When play begins: ... Every turn: ... While these have no names, they do take effect, because the preamble (the text up to the colon) tells Inform which rulebooks to copy them into - "before attacking", "when play begins", "every turn". The preamble can alternatively quote a name but no rulebook: This is the evacuating New York rule: ... creates a named rule ("the evacuating New York rule"), but one that may never happen; it belongs to none of the rulebooks, and will not occur unless we call on it to do so. Finally, the preamble can specify both a name and a rulebook, as in these examples: Before attacking the dog (this is the cruelty to animals rule): ... When play begins (this is the choose a murderer rule): ... Every turn (this is the repeat offender rule): ... When rules (and rulebooks) are intended for others to use, as is the case when we are creating an extension, it is important to be disciplined in creating rulebooks which allow the maximum flexibility. Each distinguishable step in any process should be placed in its own rule, which should be named. (We can be more relaxed with rulebooks intended only for use in a single work.) 4. Two situations are elaborate enough that Inform groups together a whole set of rulebooks to cope with them. One situation is checking the validity of, and then carrying out and describing, an action. Each different action (such as "taking") has its own rulebooks (such as "carry out taking"). Actions are essentially things done by the fictional people in our model world. An activity is something done by the computer as part of the machinery which keeps the model world running smoothly. An activity is nothing more than a set of three rulebooks: one to happen before the activity, one which performs the task in question, and one to happen when it is done. So guiding the behaviour of activities is a matter of adding new rules to existing rulebooks, just as it is with guiding the behaviour of actions. 5. While not everything done by the computer is arranged as an activity - that could become very slow and inefficient - activities do provide very many "hooks" on which we can hang new rules of our own, changing how things are done. The activities built into Inform concentrate on providing facilities which would otherwise be very difficult to arrange, or on providing conveniences for situations where IF authors have historically wanted specialized control. That doesn't mean we can't add our own activities where we like. Sometimes it is simply convenient to handle a complicated decision process (typically one that is full of exceptional cases) by setting it up as an activity, rather than making it a long and messy phrase. (Instances of this can be found in "The Reliques of Tolti-Aph".) Another useful trick is to take an existing single rule and build a whole activity on top of it. For instance, the example "Crusoe" shows how to build an activity around printing the description of an object. 6. As well as regulating what happens and how it happens, rulebooks also help to organise the division of text into paragraphs with skipped lines dividing them. In general, when text is printed by two different rules, this text is automatically put into two different paragraphs, unless instructions are given to run paragraphs on. However, this does not apply with rulebooks belonging to activities. Many activities are used for printing purposes, and it would be mayhem if they were allowed to spawn paragraph breaks all of their own. 7. We rarely need to give explicit instructions to follow a rule. If it has been put into the right rulebook, and the rulebook is one which Inform follows as a matter of routine, then the rule will be followed just when we want it to be. However, we can make Inform follow any rulebook (or even any individual named rule) at any point during play with one of the following phrases: follow the birdsong rules; consider the birdsong rules; abide by the birdsong rules; or, if the rulebook to be consulted is based on some value: follow the birdsong rules for the resplendent trogon; consider the birdsong rules for the resplendent trogon; abide by the birdsong rules for the resplendent trogon; With follow, we check procedural rules (see below) that might affect the birdsong rules, then carry them out. With consider or abide by, procedural rules are not consulted. With abide by, we carry out the birdsong rules, then make the result of those rules the result of the current rule as well. Rules can produce the result "rule succeeds" or "rule fails", or they can return a more complex response ("rule succeeds with result red", "rule fails with result the tiger"). They can also defer making a decision, with "make no decision"; in that case, neither success nor failure is decided on, and Inform can go on to the next rule in the rulebook, if there is one. 8. Whenever we have triggered a rule or rulebook that produces a result, we can check that result immediately afterward by saying if the rule succeeded... if the rule failed... if the result of the rule is a man... For a number of rulebooks built into Inform, more explicit wordings are allowed, simply to make the source text easier to read. For instance: A persuasion rule: persuasion succeeds. (Or persuasion fails.) A rule for reaching inside the magnetic shell: allow access. (Or deny access.) Visibility rule: there is sufficient light. (Or there is not sufficient light). These explicit wordings are named outcomes, and are defined so: Visibility rules have outcomes there is sufficient light (failure) and there is insufficient light (success). Defaults may be added like this: Visibility rules have outcomes there is sufficient light (failure) and there is insufficient light (success - default). After we have triggered a rule or rulebook, we may refer to the outcome as the outcome of the rulebook In the case of the visibility rules just mentioned, the default result of the rule would be "success" and the default outcome "there is sufficient light". 9. In any rulebook, earlier rules have priority over later ones: often, by declaring success or failure, an earlier rule will prevent later ones even being asked. This means that the ordering of rulebooks is very important. Inform automatically sorts the rules in order of their applicability, so that more specific rules come before less specific ones, on the grounds that special cases ought to take priority over general procedures. The laws for rule ordering are described in the previous section for reference. We can also exert a little control over the order of a rulebook by explicitly defining a first or last rule. If we prefer to control the rule ordering explicitly, we may place (or replace) rules with such statements as The collapsing bridge rule is listed first [or last] in the instead rules. The collapsing bridge rule is listed before [or after] the moving doorways rule in the instead rules. My darkness rule is listed instead of the can't act in the dark rule in the visibility rules. The can't act in the dark rule is not listed in the visibility rules. The can't remove from people rule is not listed in any rulebook. These phrases are most often useful for meddling with the contents of the standard rules or of extensions by other authors, since rules we write ourselves are likely already to be in the desired order. If we need more, we must reach for the procedural rules. Chapter 19: Advanced Text 19.1. Ordinary text and indexed text So far, we have dealt with text as something which comes in little packets: we have printed it out, read it in from the keyboard, and compared it with other text. But we have never tried to open the packets and get at the contents, letter by letter, or to make any alterations, or look for certain combinations of letters. These tricks are surprisingly seldom needed - a surprise, that is, given that everything Inform does is textual - but they are in fact open to us. Inform has two kinds of value for text: the one called simply "text", and another not mentioned until now called "indexed text". Indexed text is so called because it can be accessed by index - that is, we can if we wish get at or modify character number 1, character number 2, and so on. (1, 2, ... is the index number: this is not anything to do with a project's Index.) Text and indexed text are stored in fundamentally different ways, but Inform manages the difference automatically, and very often we can forget it. For instance: if character number 2 in WHATEVER is "a", ... clearly needs WHATEVER to be indexed - otherwise there would be no way to get at its second letter. But Inform notices this and automatically converts WHATEVER in order to make the test. So, for instance, faced with if character number 1 in "[score]" is "7", ... Inform notices that "[score]", which is a text, is being used in a situation where indexed text is needed, and ensures that it is converted before use. 19.2. Memory limitations with indexed text Because Inform helps us to pretend that dynamic text is as easy to handle as numbers, we can often forget all about the difference between text and indexed text (until we get to creating variables, properties and table columns, anyway). But it's best to be aware that this really is a pretence. The following warnings are rather like the tiny print about side-effects on medicine bottles: that is, we mostly ignore them, and if the drugs should kill us, well, at least we have the consolation of knowing we were warned. Inform creates "story files" for very small virtual computers (capable of running on phones, for instance) where memory is tight. If we create a number variable and keep on adding 1 to it, the value simply gets bigger. But if we make some text and keep on adding a letter "x" to it, the text takes up more and more space, growing into longer and longer runs of "x"s until there is no more space to hold it. There are basically three limitations on indexed text: (1) An amount of memory has to be set aside for indexed text (and other flexible-sized data), and Inform guesses the amount needed. The amount can be increased with a use option, like so: Use dynamic memory allocation of at least 16384. Inform raises its estimate of the amount needed to ensure that this amount is always at least its own guess, and also at least any amount declared like this. (And then it rounds up to the nearest power of 2, as it happens.) The default value of "dynamic memory allocation" is 8192. Glulx story files have the advantage here that, if they find themselves running on version 3.1.0 or later of the Glulx machine, they can use Glulx's new memory allocation features to grow their own memories as necessary, so that there are no hard limits at all. (2) When text is changed into indexed text, there may a maximum length it cannot exceed. The maximum is normally 1000 characters, which ought to be plenty, but can be raised by sentences such as: Use maximum indexed text length of at least 2000. What happens if this is broken, that is, if we try to use text overrunning this length? The Z-machine may simply crash, so if there is any chance that any single indexed text may grow unpredictably large, Glulx should always be used. On Glulx, overrunning text is truncated safely, except that under Glulx 3.1.0 or better the story file will try to use dynamic memory allocation to expand the limit as needed to avoid truncation. (Testing shows that text is slow to manipulate once it grows beyond about 20,000 characters in length, but this is not really surprising.) (3) Under the Z-machine, indexed text may only contain characters from the so-called "ZSCII" character set - standard numbers, letters, punctuation marks and the commonest West European accented letters. Anything more exotic is likely to be flattened into a question mark "?". Under Glulx, any character can be used. All of this makes the Z-machine sound very inferior, for indexed text purposes. But note that Z can handle all of the examples in this chapter perfectly happily. 19.3. Characters, words, punctuated words, unpunctuated words, lines, paragraphs Suppose we have some text called, once again, WHATEVER. Inform can get at its contents in a variety of ways. The lowest-level is by character - a character is a letter, digit, punctuation symbol, space or other letter-form. (We use the term "character" rather than "letter" because otherwise we would have to call "5" a letter, and so on.) Characters number upwards from 1: character number 1, to repeat that, starts the text. We can get the Nth character with:

character number (number) in (indexed text) ... indexed text
This phrase produces the Nth character from the text, counting from 1. Characters include letters, digits, punctuation symbols, spaces or other letter-forms. Example: character number 8 in "numberless projects of social reform" produces "e". If the index is less than 1 or more than the length of the text, the result is an empty text, "".
The maximum character number varies with the current length of the text, and can be evaluated as:

number of characters in (indexed text) ... number
This phrase produces the number of characters from the text. Characters include letters, digits, punctuation symbols, spaces or other letter-forms. Examples: number of characters in "War and Peace" number of characters in "" produce 13 and 0 respectively.
When an indexed text has 0 characters, it is "empty", just as for ordinary text; and otherwise it is "non-empty". We can also extract the contents by word, again numbered from 1. Thus:

word number (number) in (indexed text) ... indexed text
This phrase produces the Nth word from the text, counting from 1. Words for this purpose are what's left after breaking the text up at punctuation or spacing (spaces, line breaks, paragraph breaks) and then removing that punctuation or spacing. Example: word number 3 in "ice-hot, don't you think?" produces "don't". If the index is less than 1 or more than the number of words in the text, the result is an empty text, "".

number of words in (indexed text) ... number
This phrase produces the number of words from the text. Words for this purpose are what's left after breaking the text up at punctuation or spacing (spaces, line breaks, paragraph breaks) and then removing that punctuation or spacing. Example: number of words in "ice-hot, don't you think?" produces 5.
Note that the contraction apostrophe in "don't" doesn't count as punctuation. Because this is not always quite what we want, Inform offers two variations:

punctuated word number (number) in (indexed text) ... indexed text
This phrase produces the Nth word from the text, counting from 1. Words for this purpose are what's left after breaking the text up at punctuation or spacing (spaces, line breaks, paragraph breaks) and then removing the spacing, but leaving the punctuation as independent words. Example: punctuated word number 2 in "ice-hot, don't you think?" produces "-". The punctuated words here are "ice", "-", "hot", ",", "don't", "you", "think", "?". If two or more punctuation marks are adjacent, they are counted as different words, except for runs of dashes or periods: thus ",," has two punctuated words, but "--" and "..." have only one each. If the index is less than 1 or more than the number of punctuated words in the text, the result is an empty text, "".

number of punctuated words in (indexed text) ... number
This phrase produces the number of words from the text. Words for this purpose are what's left after breaking the text up at punctuation or spacing (spaces, line breaks, paragraph breaks) and then removing the spacing, but leaving the punctuation as independent words. Example: number of punctuated words in "ice-hot, don't you think?" produces 8; see if you can find them all.

unpunctuated word number (number) in (indexed text) ... indexed text
This phrase produces the Nth word from the text, counting from 1. Words for this purpose are what's left after breaking the text up at spacing (spaces, line breaks, paragraph breaks) but including all punctuation as if it were part of the spelling of the words it joins to. Example: unpunctuated word number 1 in "ice-hot, don't you think?" produces "ice-hot,". The unpunctuated words in "ice-hot, don't you think?" are "ice-hot,", "don't", "you", "think?". If the index is less than 1 or more than the number of punctuated words in the text, the result is an empty text, "".

number of unpunctuated words in (indexed text) ... number
This phrase produces the number of words from the text. Words for this purpose are what's left after breaking the text up at spacing (spaces, line breaks, paragraph breaks) but including all punctuation as if it were part of the spelling of the words it joins to. Example: number of unpunctuated words in "ice-hot, don't you think?" produces just 4.
Finally, on the larger scale still, we also have:

line number (number) in (indexed text) ... indexed text
This phrase produces the Nth line from the text, counting from 1. Unless explicit use is made of line-breaking, lines and paragraphs will be the same - it doesn't refer to lines as visible on screen, because we have no way of knowing what size screen the player might have.

number of lines in (indexed text) ... number
This phrase produces the number of lines in the text. Unless explicit use is made of line-breaking, lines and paragraphs will be the same - it doesn't refer to lines as visible on screen, because we have no way of knowing what size screen the player might have. Example: the number of lines in "Sensational news just in![paragraph break]The Martians have invaded Miranda.[line break](One of the moons of Uranus, that is.)" is 3.

paragraph number (number) in (indexed text) ... indexed text
This phrase produces the Nth paragraph from the text, counting from 1.

number of paragraphs in (indexed text) ... number
This phrase produces the number of paragraphs in the text. Example: the number of paragraphs in "Sensational news just in![paragraph break]The Martians have invaded Miranda.[line break](One of the moons of Uranus, that is.)" is 2.
(Attempting to make large enough texts to have a serious paragraph count is slightly risky if there is not much memory to play with, as on the Z-machine. But the facilities do exist.) 19.4. Upper and lower case letters In most European languages the same letters can appear in two forms: as capitals, like "X", mainly used to mark a name or the start of a sentence; or in their ordinary less prominent form, like "x". These forms are called upper and lower case because, historically, typesetters kept lead castings of letters in two wooden cases, one above the other on the workbench. Lower case letters were in the lower box closer to hand, being more often needed. Human languages are complicated. Not every lower case letter has an upper case partner: ordinal markers in Hispanic languages don't, for instance, and the German "ß" is never used in upper case. Sometimes two different lower case letters have the same upper case form: "ς" and "σ", two versions of the Greek sigma, both capitalise to "Σ". Inform follows the international Unicode standard in coping with all this. We can test whether text is in either case like so:

if (indexed text) is in lower case:
This condition is true if every character in the text is a lower case letter. Examples: this is true for "wax", but false for "wax seal" or "eZ mOnEy".

if (indexed text) is in upper case:
This condition is true if every character in the text is in upper case. Examples: this is true for "BEESWAX", but false for "ROOM 101".
We can change the casing of text using:

(indexed text) in lower case ... indexed text
This phrase produces a new version of the given text, but with all upper case letters reduced to lower case. Example: "a ticket to Tromsø via Østfold" becomes "a ticket to tromsø via østfold"

(indexed text) in upper case ... indexed text
This phrase produces a new version of the given text, but with all upper case letters reduced to lower case. Example: "a ticket to Tromsø via Østfold" becomes "A TICKET TO TROMSØ VIA ØSTFOLD"

(indexed text) in title case ... indexed text
This phrase produces a new version of the given text, but with casing of words changed to title casing: this capitalises the first letter of each word, and lowers the rest. Example: "a ticket to Tromsø via Østfold" becomes "A Ticket To Tromsø Via Østfold"

(indexed text) in sentence case ... indexed text
This phrase produces a new version of the given text, but with casing of words changed to sentence casing: this capitalises the first letter of each sentence and reduces the rest to lower case. Example: "a ticket to Tromsø via Østfold" becomes "A ticket to tromsø via østfold"
Accents are preserved in case changes. So (if we are using Glulx and have Unicode available) title case can turn Aristophanes' discomfortingly lower-case lines ἐξ οὗ γὰρ ἡμᾶς προὔδοσαν μιλήσιοι, οὐκ εἶδον οὐδ᾽ ὄλισβον ὀκτωδάκτυλον, ὃς ἦν ἂν ἡμῖν σκυτίνη "πικουρία by raising them proudly up like so: Ἐξ Οὗ Γὰρ Ἡμᾶς Προὔδοσαν Μιλήσιοι, Οὐκ Εἶδον Οὐδ᾽ Ὄλισβον Ὀκτωδάκτυλον, Ὃς Ἦν Ἂν Ἡμῖν Σκυτίνη "Πικουρία. Title and sentence casing can only be approximate if done by computer. Inform looks at the letters, but is blind to the words and sentences they make up. (Note the way sentence casing did not realise "Tromsø" and "Østfold" were proper nouns.) If asked to put the name "MCKAY" into title casing, Inform will opt for "Mckay", not recognising this as the Scottish patronymic surname "McKay". Given "baym dnieper", the title of David Bergelson's great Yiddish novel of 1932, it will opt for "BAYM DNIEPER": but properly speaking Yiddish does not have upper case lettering at all, though nowadays it is sometimes printed as if it did. And conventions are very variable about which words should be capitalised in titles: English publishers mostly agree that connectives, articles and prepositions should be in lower case, but in France almost anything goes, with Académie Française rules giving way to avant-garde book design. In short, we cannot rely on Inform's title casing to produce a result which a human reader will always think perfect. This discussion has all been about how Inform prints, not about how it reads commands from the keyboard, because the latter is done case-insensitively. The virtual machines for which Inform creates programs normally flatten all command input to lower case, and in any case Understand comparison ignores casing. Thus Understand "mckay" as the Highland Piper. means that "examine McKay", "examine MCKAY", "examine mckay", and so forth are all equivalent. The text of the player's command probably doesn't preserve the original casing typed in any event. One more caution, though it will affect hardly anyone. For projects using the Z-machine, only a restricted character set is available in indexed texts: for more, we must use Glulx. A mad anomaly of ZSCII, the Z-machine character set, is that it contains the lower case letter "ÿ" but not its upper case form "Ÿ", so that "ÿ" in upper case produces "Ÿ" in Glulx but "ÿ" in the Z-machine. This will come as a blow to Queensrÿche fans, but in all other respects any result on the Z-machine should agree with its counterpart on Glulx. Example 401 (*): Rocket Man Using case changes on any text produced by a "to say..." phrase. Example 402 (*): Capital City To arrange that the location information normally given on the left-hand side of the status line appears in block capitals. 19.5. Matching and exactly matching Up to now, we have only been able to judge two texts by seeing if they are equal, but we can now ask more subtle questions.

if (indexed text) matches the text (indexed text):
This condition is true if the second text occurs anywhere inside the first. Examples: if "[score]" matches the text "3", ... tests whether the digit 3 occurs anywhere in the score, as printed out; and if the printed name of the location matches the text "the", ... tests to see whether "the" can be found anywhere in the current room's name. Note that the location "Smotheringly Hot Jungle" would pass this test - it's there if you look. On the other hand, "The Orangery" would not, because "The" does not match against "the". We can get around this in a variety of ways, one of which is to tell Inform to be insensitive to the case (upper or lower) of letters: if the printed name of the location matches the text "the", case insensitively: ...

if (indexed text) exactly matches the text (indexed text):
This condition is true if the second text matches the first, starting at the beginning and finishing at the end. This appears to be the same as testing if one is equal to the other, but that's not quite true: for example, if "[score]" exactly matches "[best score]", ... is true if the score and best score currently print out as the same text, which will be true if they are currently equal as numbers; but if "[score]" is "[best score]", ... is never true - these are different texts, even if they sometimes look the same.
In the next section we shall see that "matches" and "exactly matches" can do much more than the simple text matching demonstrated above. We can also see how many times something matches:

number of times (indexed text) matches the text (indexed text) ... number
This produces the number of times the second text occurs within the first. The matches are not allowed to overlap. Example: number of times "pell-mell sally" matches the text "ll" = 3 number of times "xyzzy" matches the text "Z" = 0 number of times "xyzzy" matches the text "Z", case insensitively = 2 number of times "aaaaaaaa" matches the text "aaaa" = 2
There's no "number of times WHATEVER exactly matches the text FIND" phrase since this is by definition going to have to be 0 or 1. 19.6. Regular expression matching When playing around with text, we tend to get into longer and trickier wrangles of matching - we find that we want to look not for simple text like "gold", but for "gold" used only as a separate word, or for a date in YYYY-MM-DD format, or for a seemingly endless range of other possibilities. What we need is not just for Inform to provide a highly flexible matching program, but also a good notation in which to describe what we want. Fortunately, such a notation already exists. This is the "regular expression" notation, named for a 1950s mathematical model by the logician Stephen Kleene, applied to computing in the late 60s by Ken Thompson, borrowed almost at once by the early Unix tools of the 70s, and developed further by Henry Spencer in the 80s and Philip Hazel in the 90s. The glue holding the Internet together - the Apache web-server, the scripting languages Perl and Python, and so forth - makes indispensable use of regular expressions. As might be expected from the previous section, we simply have to describe the FIND text as "regular expression" rather than "text" and then the same facilities are available:

if (indexed text) matches the regular expression (indexed text):
This condition is true if any contiguous part of the text can be matched against the given regular expression. Examples: if "taramasalata" matches the regular expression "a.*l", ... is true, since this looks for a part of "taramasalata" which begins with "a", continues with any number of characters, and finishes with "l"; so it matches "asal". The option "case insensitively" causes lower and upper case letters to be treated as equivalent.

if (indexed text) exactly matches the regular expression (indexed text):
This condition is true if the whole text (starting from the beginning and finishing at the end) can be matched against the given regular expression. The option "case insensitively" causes lower and upper case letters to be treated as equivalent.
And once again:

number of times (indexed text) matches the regular expression (indexed text) ... number
This produces the number of times that contiguous pieces of the text can be matched against the regular expression, without allowing them to overlap.
Since a regular expression can match quite a variety of possibilities (for instance "b\w+t" could match "boast", "boat", "bonnet" and so on), it's sometimes useful to find what the match actually was:

text matching regular expression ... indexed text
This phrase is only meaningful immediately after a successful match of a regular expression against text, and it produces the text which matched. Example: if "taramasalata" matches the regular expression "m.*l": say "[text matching regular expression]."; says "masal."
Perhaps fairly, perhaps not, regular expressions have a reputation for being inscrutable. The basic idea is that although alphanumeric characters (letters, numbers and spaces) mean just what they look like, punctuation characters are commands with sometimes dramatic effects. Thus: if WHATEVER matches the regular expression "fish", ... if WHATEVER matches the regular expression "f.*h", ... behave very differently. The first is just like matching the text "fish", but the second matches on any sequence of characters starting with an "f" and ending with an "h". This is not at all obvious at first sight: reading regular expressions is a skill which must be learned, like reading a musical score. A really complex regular expression can look like a soup of punctuation and even an expert will blink for a few minutes before telling you what it does - but a beginner can pick up the basics very quickly. Newcomers might like to try out and become comfortable with the features a few at a time, reading down the following list. 1. Golden rule. Don't try to remember all the characters with weird effects. Instead, if you actually mean any symbol other than a letter, digit or space to be taken literally, place a backslash "\" in front of it. For instance, matching the regular expression "\*A\* of the Galactic Patrol" is the same as matching the text "*A* of the Galactic Patrol", because the asterisks are robbed of their normal powers. This includes backslash itself: "\\" means a literal backslash. (Don't backslash letters or digits - that turns out to have a meaning all its own, but anyway, there is never any need.) 2. Alternatives. The vertical stroke "|" - not a letter I or L, nor the digit 1 - divides alternatives. Thus "the fish|fowl|crawling thing" is the same as saying match "the fish", or "fowl", or "crawling thing". 3. Dividing with brackets. Round brackets "(" and ")" group parts of the expression together. "the (fish|fowl|crawling thing) in question" is the same as saying match "the fish in question", or "the fowl in question", or "the crawling thing in question". Note that the "|" ranges outwards only as far as the group it is in. 4. Any character. The period "." means any single character. So "a...z" matches on any sequence of five characters so long as the first is "a" and the last is "z". 5. Character alternatives. The angle brackets "<" and ">" are a more concise way of specifying alternatives for a single character. Thus "bb" matches on "bab", "beb", "bib", "bob" or "bub", but not "baob" or "beeb" - any single character within the angle brackets is accepted. Beginning the range with "^" means "any single character so long as it is not one of these": thus "b<^aeiou>b" matches on "blb" but not "bab", "beb", etc., nor on "blob" or "bb". Because long runs like this can be a little tiresome, we are also allowed to use "-" to indicate whole ranges. Thus "bb" matches a "b", then any lower case English letter, then another "b". In traditional regular expression language, square brackets rather than angle brackets are used for character ranges. In fact Inform does understand this notation (it treats square and angle brackets equally for this purpose), but square brackets would be annoying to type, since they already have a meaning in quoted text - for text substitutions. 6. Popular character ranges. The range "", matching any decimal digit, is needed so often that it has an abbreviation: "\d". Thus "\d\d\d\d-\d\d-\d\d" matches, say, "2006-12-03". Similarly, "\s" means "any spacing character" - a space, tab or line break. "\p" is a punctuation character, in the same sense used for word division in the previous section: it actually matches any of . , ! ? - / " : ; ( ) [ ] { } "\w" means "any character appearing in a word", and Inform defines it as anything not matching "\s" or "\p". "\l" and "\u" match lower and upper case letters, respectively. These are much stronger than "" and "", since they use the complete definition in the Unicode 4.0.0 standard, so that letter-forms from all languages are catered for: for example "δ" matches "\l" and "Δ" matches "\u". The reverse of these is achieved by capitalising the letter. So "\D" means "anything not a digit", "\P" means "anything not punctuation", "\W" means "anything not a word character", "\L" means "anything not a lower case letter" and so on. 7. Positional restrictions. The notation "^" does not match anything, as such, but instead requires that we be positioned at the start of the text. Thus "^fish" matches only "fish" at the start of the text, not occurring anywhere later on. Similarly, "$" requires that the position be the end of the text. So "fish$" matches only if the last four characters are "fish". Matching "^fish$" is the same thing as what Inform calls exactly matching "fish". Another useful notation is "\b", which matches a word boundary: that is, it matches no actual text, but requires the position to be a junction between a word character and a non-word character (a "\w" and a "\W") or vice versa. Thus "\bfish\b" matches "fish" in "some fish" and also "some fish, please!", but not in "shellfish". (The regular expression "\w*fish\b" catches all words ending in "fish", as we will see below.) As usual, the capitalised version "\B" negates this, and means "not at a word boundary". 8. Line break and tab. The notations "\n" and "\t" are used for a line break ("n" for "new line") and tab, respectively. Tabs normally do not occur in Inform strings, but can do when reading from files. It makes no sense to reverse these, so "\N" and "\T" produce errors. 9. Repetition. Placing a number in braces "{" and "}" after something says that it should be repeated that many times. Thus "ax{25}" matches only on "axxxxxxxxxxxxxxxxxxxxxxxxx". More usefully, perhaps, we can specify a range of the number of repetitions: "ax{2,6}" matches only on "axx", "axxx", "axxxx", "axxxxx", "axxxxxx". And we can leave the top end open: "ax{2,}" means "a" followed by at least two "x"s. Note that the braces attach only to most recent thing - so "ax{2}" means "a" followed by two of "x" - but, as always, we can use grouping brackets to change that. So "(ax){2,}" matches "axax", "axaxax", "axaxaxax",... (It's probably best not to use Inform to try to match the human genome against "{3000000000}", but one of the most important practical uses of regular expression matching in science is in treating DNA as a string of nucleotides represented by the letters "a", "c", "g", "t", and looking for patterns.) 10. Popular repetitions. Three cases are so often needed that they have standard short forms: "{0,1}", which means 0 or 1 repetition of something - in other words, doesn't so much repeat it as make it optional - is written "?". Thus "ax?y" matches only on "ay" or "axy". "{0,}", which means 0 or more repetitions - in other words, any number at all - is written "*". Thus "ax*y" matches on "ay", "axy", "axxy", "axxxy", ... and the omnivorous ".*" - which means "anything, any number of times" - matches absolutely every text. "{1,}", which means 1 or more repetitions, is written "+". So "\d+" matches any run of digits, for instance. 11. Greedy vs lazy. Once we allow things to repeat an unknown number of times, we run into an ambiguity. Sure, "\d+" matches the text "16339b". But does it look only as far as the "1", then reason that it now has one or more digits in a row, and stop? Or does it run onward devouring digits until it can do so no longer, so matching the "16339" part? These two strategies are called "lazy" and "greedy" respectively. Do we care? Well, the strategy used makes no difference to whether there is a match, but it does affect what part of the text is matched, and the number of matches there are. Unless we mark for it, all repetitions are greedy. Usually this is good, but it means that, for instance, "-.+-" applied to "-alpha- -beta- -gamma-" will match the whole text, because ".+" picks up all of "alpha- -beta- -gamma". To get around this, we can mark any of the repetition operators as lazy by adding a question mark "?". Thus: "-.+?-" applied to "-alpha- -beta- -gamma-" matches three times, producing "-alpha-" then "-beta-" then "-gamma-". A logical but sometimes confusing consequence is that a doubled question mark "??" means "repeat 0 or 1 times, but prefer 0 matches to 1 if both are possibilities": whereas a single question mark "?", being greedy, means "repeat 0 or 1 times, but prefer 1 match to 0 if both are possibilities". 12. Numbered groups. We have already seen that round brackets are useful to clump together parts of the regular expression - to choose within them, or repeat them. In fact, Inform numbers these from 1 upwards as they are used from left to right, and we can subsequently refer back to their contents with the notation "\1", "\2", ... After a successful match, we can find the results of these subexpressions with:

text matching subexpression (number) ... indexed text
This phrase is only meaningful immediately after a successful match of a regular expression against text, and it produces the text which matched. The number must be from 1 to 9, and must correspond to one of the bracketed groups in the expression just matched. Example: after if "taramasalata" matches the regular expression "a(r.*l)a(.)": the "text matching regular expression" is "aramasalat", the "text matching subexpression 1" is "ramasal", and "text matching subexpression 2" is "t".
For instance: "(\w)\w*\1" matches any run of two or more word-characters, subject to the restriction that the last one has to be the same as the first - so it matches "xerox" but not "alphabet". When Inform matches this against "xerox", first it matches the initial "x" against the group "(\w)". It then matches "\w*" ("any number of word-characters") against "ero", so that the "*" runs up to 3 repetitions. It then matches "\1" against the final "x", because "\1" requires it to match against whatever last matched in sub-expression 1 - which was an "x". Numbered groups allow wicked tricks in matching, it's true, but really come into their own when it comes to replacing - as we shall see. 13. Switching case sensitivity on and off. The special notations "(?i)" and "(?-i)" switch sensitivity to upper vs. lower case off and on, mid-expression. Thus "a(?i)bcd(?-i)e" matches "abcde", "aBcDe", etc., but not "Abcde" or "abcdE". 14. Groups with special meanings. This is the last of the special syntaxes: but it's a doozy. A round-bracketed group can be marked to behave in a special way by following the open bracket by a symbol with a special meaning. Groups like this have no number and are not counted as part of \1, \2, and so forth - they are intended not to gather up material but to have some effect of their own. "(# ...)" Is a comment, that is, causes the group to do nothing and match against anything. "(?= ...)" Is a lookahead: it is a form of positional requirement, like "\b" or "^", but one which requires that the text ahead of us matches whatever is in the brackets. (It doesn't consume that text - only checks to see that it's there.) For instance "\w+(?=;)" matches a word followed by a semicolon, but does not match the semicolon itself. "(?! ...)" Is the same but negated: it requires that the text ahead of us does not match the material given. For instance, "a+(?!z)" matches any run of "a"s not followed by a "z". "(?<= ...)" and "(? ...)" Is a possessive, that is, causes the material to be matched and, once matched, never lets go. No matter what subsequently turns out to be convenient, it will never change its match. For instance, "\d+8" matches against "768" because Inform realises that "\d+" cannot be allowed to eat the "8" if there is to be a match, and stops it. But "(>\d+)8" does not match against "768" because now the "\d+", which initially eats "768", is possessive and refuses to give up the "8" once taken. "(?(1)...)" and "(?(1)...|...)" Are conditionals. These require us to match the material given if \1 has successfully matched already; in the second version, the material after the "|" must be matched if \1 has not successfully matched yet. And the same for 2, 3, ..., 9, of course. Finally, conditionals can also use lookaheads or lookbehinds as their conditions. So for instance: "(?(?=\d)\d\d\d\d|AY-\d\d\d\d)" means if you start with a digit, match four digits; otherwise match "AY-" followed by four digits. There are easier ways to do this, of course, but the really juicy uses of conditionals are only borderline legible and make poor examples - perhaps this is telling us something. Example 403 (*): About Inform's regular expression support Some footnotes on Inform's regular expressions, and how they compare to those of other programming languages. Example 404 (*): Alpha Creating a beta-testing command that matches any line starting with punctuation. 19.7. Indexed text in variables, properties and tables So far we have been able to ignore the difference between "text" and "indexed text" because Inform has always been able to convert the former to the latter when needed. But the reverse conversion cannot be made. Ordinary text is stored in a specially compacted, read-only form: it's really part of the program, not part of the data. The upshot of this is that if we need a variable to contain text which can be internally altered during play, then we must declare this. Instead of writing The player's forename is a text that varies. we must write: The player's forename is an indexed text that varies. Similarly for a property: A person has an indexed text called nickname. For a named "let" value, we have a dilemma. These are normally created by writing something like: let the target be 17; and Inform looks at the value - here 17, a number - to deduce that the new value, called "target", must be a number. So if we write: let the target be "excellent"; the result is that "target" is just a text, not an indexed text. We get around this by writing instead: let the target be an indexed text; which creates the value, initially having the empty text as contents, and then let the target be "excellent"; to subsequently set its initial state. The same issue arises for table columns, because we are allowed to simply write out values in table columns, and let Inform work out what kind they are. If there are blank entries, we can always write in the kind of value by hand, but suppose the entries are initially all filled in? The answer is that we can imitate this: Table of Neptune's Moons moon surface (indexed text) "Nereid" "utterly unknown" "Triton" "cryovolcanic ridges" "Proteus" "highly irregular and sooty" Here the two columns are called "moon" and "surface", so we can talk about the "moon entry" and the "surface entry" once a row has been chosen: but the moon entry is text, and the surface entry is indexed text. Lastly, suppose we want to define new phrases which deal with text. Here we have two things to remember. First, we need to say that the value decided is indexed text, not text; secondly, that text converts to indexed text by magic, but not vice versa. So: To decide what indexed text is (T - text) doubled: decide on "[T][T]". works fine so long as we only want to pass text to it, but would not let us double indexed text. This, on the other hand, handles both: To decide what indexed text is (T - indexed text) doubled: decide on "[T][T]". So for instance: say "Neptune" doubled. prints "NeptuneNeptune" because Inform automatically converts "Neptune" to indexed text when "doubled" is used on it. Example 405 (*): Identity Theft Allowing the player to enter a name to be used for the player character during the game. Example 406 (*): Mirror, Mirror The sorcerer's mirror can, when held up high, form an impression of its surroundings which it then preserves. Example 407 (**): The Cow Exonerated Creating a class of matches that burn for a time and then go out, with elegant reporting when several matches go out at once. 19.8. Replacements Suppose V is an indexed text which varies - perhaps a property of something, or a variable defined everywhere, or a temporary "let"-named value. How do we change its contents? The easiest way is simply to assign text to it. Thus: let V be "It is now [the time of the day in words]." And, for instance, let V be "[V]!" adds an exclamation mark at the end of V. Otherwise, it is more useful (also a little faster) to modify V by changing its characters, words and so on. Thus:

replace character number (number) in (indexed text) with (indexed text)
This phrase acts on the named text by placing the given text in place of the Nth character, counting from 1. Example: let V be an indexed text; let V be "mope"; replace character number 3 in V with "lecul"; say V; says "molecule".

replace word number (number) in (indexed text) with (indexed text)
This phrase acts on the named text by placing the given text in place of the Nth word, counting from 1, and dividing words at spacing or punctuation. Example: let V be an indexed text; let V be "Does the well run dry?"; replace word number 3 in V with "jogger"; say V; says "Does the jogger run dry?".

replace punctuated word number (number) in (indexed text) with (indexed text)
This phrase acts on the named text by placing the given text in place of the Nth word, counting from 1, and dividing words at spacing, counting punctuation runs as words in their own right. Example: let V be an indexed text; let V be "Frankly, yes, I agree."; replace punctuated word number 2 in V with ":"; say V; says "Frankly: yes, I agree.".

replace unpunctuated word number (number) in (indexed text) with (indexed text)
This phrase acts on the named text by placing the given text in place of the Nth word, counting from 1, and dividing words at spacing, counting punctuation as part of a word just as if it were lettering. Example: let V be an indexed text; let V be "Frankly, yes, I agree."; replace unpunctuated word number 2 in V with "of course"; say V; says "Frankly, of course I agree.".

replace line number (number) in (indexed text) with (indexed text)
This phrase acts on the named text by placing the given text in place of the Nth line, counting from 1. Lines are divided by paragraph or line breaks.

replace paragraph number (number) in (indexed text) with (indexed text)
This phrase acts on the named text by placing the given text in place of the Nth paragraph, counting from 1.
Last, but not least, we can replace text wherever it occurs:

replace the text (indexed text) in (indexed text) with (indexed text)
This phrase acts on the named text by searching and replacing, as many non-overlapping times as possible. Example: replace the text "a" in V with "z" changes every lower-case "a" to "z": the same thing done with the "case insensitively" option would change each "a" or "A" to "z".
All very well for letters, but it can be unfortunate to try replace the text "Bob" in V with "Robert" if V happens to contain, say "The Olympic Bobsleigh Team": it would become "The Olympic Robertsleigh Team". What we want, of course, is for Bob to become Robert only when it's a whole word. We can get that with:

replace the word (indexed text) in (indexed text) with (indexed text)
This phrase acts on the named text by searching and replacing, as many non-overlapping times as possible, where the search text must occur as a whole word. Example: replace the word "Bob" in V with "Robert" changes "Bob got on the Bobsleigh" to "Robert got on the Bobsleigh".

replace the punctuated word (indexed text) in (indexed text) with (indexed text)
This phrase acts on the named text by searching and replacing, as many non-overlapping times as possible, where the search text must occur as a whole word or run of punctuation.
But these are all just special cases of the grand-daddy of all replacement phrases:

replace the regular expression (indexed text) in (indexed text) with (indexed text)
This phrase acts on the named text by matching the regular expression and replacing anything which fits it, as many non-overlapping times as possible. Example: replace the regular expression "\d+" in V with "..." changes "The Battle of Waterloo, 1815, rivalled Trafalgar, 1805" to "The Battle of Waterloo, ..., rivalled Trafalgar, ...". The "case insensitively" causes lower and upper case letters to be treated as if the same letter. When replacing a regular expression, the replacement text also has a few special meanings (though, thankfully, many fewer than for the expression itself). Once again "\n" and "\t" can be used for line break and tab characters, and "\\" must be used for an actual backslash. But, very usefully, "\1" to "\9" expand as the contents of groups numbered 1 to 9, and "\0" to the exact text matched. So: replace the regular expression "\d+" in V with "roughly \0" adds the word "roughly" in front of any run of digits in V, because \0 becomes in turn whichever run of digits matched. And replace the regular expression "(\w+) (.*)" in V with "\2, \1" performs the transformation "Frank Booth" to "Booth, Frank". Finally, prefixing the number by "l" or "u" forces the text it represents into lower or upper case, respectively. For instance: replace the regular expression "\b(\w)(\w*)" in X with "\u1\l2"; changes the casing of X to "title casing", where each individual word is capitalised. (This is a little slow on large texts, since so many matches and replacements are made: it's more efficient to use the official phrases for changing case.)
Example 408 (*): Fido A dog the player can name and un-name at will. Example 409 (*): Igpay Atinlay A pig Latin filter for the player's commands. Example 410 (*): Blackout Filtering the names of rooms printed while in darkness. Example 411 (**): Mr. Burns' Repast Letting the player guess types for an unidentifiable fish. Example 412 (**): Northstar Making Inform understand ASK JOSH TO TAKE INVENTORY as JOSH, TAKE INVENTORY. This requires us to use a regular expression on the player's command, replacing some of the content. Example 413 (***): Cave-troll Determining that the command the player typed is invalid, editing it, and re-examining it to see whether it now reads correctly. 19.9. Summary of regular expression notation MATCHING Positional restrictions ^ Matches (accepting no text) only at the start of the text $ Matches (accepting no text) only at the end of the text \b Word boundary: matches at either end of text or between a \w and a \W \B Matches anywhere where \b does not match Backslashed character classes \char If char is other than a-z, A-Z, 0-9 or space, matches that literal char \\ For example, this matches literal backslash "\" \n Matches literal line break character \t Matches literal tab character (but use this only with external files) \d Matches any single digit \l Matches any lower case letter (by Unicode 4.0.0 definition) \p Matches any single punctuation mark: . , ! ? - / " : ; ( ) [ ] { } \s Matches any single spacing character (space, line break, tab) \u Matches any upper case letter (by Unicode 4.0.0 definition) \w Matches any single word character (neither \p nor \s) \D Matches any single non-digit \L Matches any non-lower-case-letter \P Matches any single non-punctuation-mark \S Matches any single non-spacing-character \U Matches any non-upper-case-letter \W Matches any single non-word-character (i.e., matches either \p or \s) Other character classes . Matches any single character Character range: matches any single character inside Negated character range: matches any single character not inside Inside a character range e-h Any character in the run "e" to "h" inclusive (and so on for other runs) >... Starting with ">" means that a literal close angle bracket is included \ Backslash has the same meaning as for backslashed character classes: see above Structural | Divides alternatives: "fish|fowl" matches either (?i) Always matches: switches to case-insensitive matching from here on (?-i) Always matches: switches to case-sensitive matching from here on Repetitions ...? Matches "..." either 0 or 1 times, i.e., makes "..." optional ...* Matches "..." 0 or more times: e.g. "\s*" matches an optional run of space ...+ Matches "..." 1 or more times: e.g. "x+" matches any run of "x"s ...{6} Matches "..." exactly 6 times (similarly for other numbers, of course) ...{2,5} Matches "..." between 2 and 5 times ...{3,} Matches "..." 3 or more times ....? "?" after any repetition makes it "lazy", matching as few repeats as it can Numbered subexpressions (...) Groups part of the expression together: matches if the interior matches \1 Matches the contents of the 1st subexpression reading left to right \2 Matches the contents of the 2nd, and so on up to "\9" (but no further) Unnumbered subexpressions (# ...) Comment: always matches, and the contents are ignored (?= ...) Lookahead: matches if the text ahead matches "...", but doesn't consume it (?! ...) Negated lookahead: matches if lookahead fails (?<= ...) Lookbehind: matches if the text behind matches "...", but doesn't consume it (? ...) Possessive: tries to match "..." and if it succeeds, never backtracks on this (?(1)...) Conditional: if \1 has matched by now, require that "..." be matched (?(1)...|...) Conditional: ditto, but if \1 has not matched, require the second part (?(?=...)...|...) Conditional with lookahead as its condition for which to match (?(?<=...)...|...) Conditional with lookbehind as its condition for which to match IN REPLACEMENT TEXT \char If char is other than a-z, A-Z, 0-9 or space, expands to that literal char \\ In particular, "\\" expands to a literal backslash "\" \n Expands to a line break character \t Expands to a tab character (but use this only with external files) \0 Expands to the full text matched \1 Expands to whatever the 1st bracketed subexpression matched \2 Expands to whatever the 2nd matched, and so on up to "\9" (but no further) \l0 Expands to \0 converted to lower case (and so on for "\l1" to "\l9") \u0 Expands to \0 converted to upper case (and so on for "\u1" to "\u9") Chapter 20: Lists 20.1. Lists and entries Many sections in this book begin by introducing a new kind of value. Reading through in order, the possibilities mount up: numbers, times, texts (and indexed texts), and so on. (See the Kinds page of the Index for a convenient list of the options.) This section is a little different: rather than showing a single new kind of value, it shows how to make a new kind out of any existing one. If K is any kind of value, then "list of K" is also a kind of value. For instance, we could write: let L be a list of numbers; and this would create a new "let" variable, called L, whose kind of value is "list of numbers". On the other hand, we are not allowed to write: let L be a list; because "list" by itself is not a kind of value. (Inform always needs to know what kinds the values entered in a list are going to have.) Lists are like flexible-length table columns, but that probably makes them sound more mysterious than they really are. A list is simply a sequence of values, called its "entries", numbered from 1 upwards. The number of entries is called its "length". If we try let L be a list of numbers; say "L has [the number of entries in L] entries."; then we find L has 0 entries. This is because all lists start out empty when created: that is, they initially have 0 entries. Inform has two built-in adjectives "empty" and "non-empty" which can apply to lists, and they mean just what they ought to mean: a list is empty if its length is 0, and otherwise non-empty. We can add entries very easily: add 2 to L; add 3 to L; add 5 to L; We can now, for instance, try saying the list: say "L is now [L]."; with the result L is now 2, 3 and 5. Note that only numbers can be added to L: if we try add "clock" to L; Inform will produce a problem message, because L has kind "list of numbers", whereas "clock" is text. In this way, Inform ensures that a list always contains values of the same kind throughout. So it's not possible to construct a list whose entries are: 2, "fish", 4 and the Entire Game Such a list would be very hazardous to deal with, in any case. If what we need is a combination of different kinds of values, tables are a better option. Finally, note that since "list of numbers" is a kind of value in its own right, so is "list of lists of numbers", and so on - though such lists are trickier to deal with, they are sometimes handy. 20.2. Constant lists It is convenient to have a concise way to write down a constant list. Just as we could write "231", say, or "7:01 AM" to refer to particular number and time constants, so we can write list constants: let L be {1, 2, 3, 4}; Inform recognises that "{1, 2, 3, 4}" is a set because of the braces, and looks at the entries inside, sees that they are numbers, and deduces that it is a constant whose kind of value is "list of numbers". L is then a temporary list variable and we can add to it, remove things, and so on as we please - {1, 2, 3, 4} is merely its initial value. When constructing sets, it is worth noting that Inform requires spaces after commas in lists like this one (which seems a little harsh, but is necessary because otherwise many sensible literal specifications for units would be impossible - anyway, the reason isn't important here). So let L be {1,2,3,4}; would produce problem messages. But Inform does not require spaces round its braces. We call this way of writing a list "brace notation". In mathematics, braces are usually used for sets, and properly speaking these are sequences not sets - so that "{1, 2, 3, 4}" is different from "{4, 3, 2, 1}" - but it is still a familiar notation. Similarly, let L be {"apple", "pear", "loganberry"}; makes L a list of texts; and The marshmallow, the firework and the stink bomb are in the Scout Hut. The list of prohibited items is a list of objects that varies. The list of prohibited items is {the firework, the stink bomb}. makes a global variable ("list of prohibited items") with kind of value "list of objects", and whose initial value is to contain two things: the firework and the stink bomb. More exotically, if we need to make lists of lists: let L be {{1, 2}, {6, 7, 8}}; gives L the kind of value "list of lists of numbers", with (initially) two entries: the list {1, 2} (a list of numbers), then the list {6, 7, 8} (ditto). Constant lists are convenient, too, when a column in a table needs to contain lists: The duck, the orange, the cider, the cinnamon and the orange are in the Kitchen. Table of Requirements recipe ingredients "duck à l'orange" {the duck, the orange} "spiced cider" {the cider, the cinnamon, the orange} A special word about the constant list "{ }". This means the list with no entries - the empty list. If we try to create a new "let" variable M with let M be { }; then Inform will produce a problem message, because it cannot tell what sort of list M will be: a list of numbers, or texts, or times, or...? On the other hand, writing let M be { }; is fine provided that M already exists, and then does the obvious thing - empties M. Similarly, a table column in which every entry is "{ }" produces a problem message unless the heading for that column spells out the kind of value stored within it: for instance, "ingredients (list of texts)". All of this is a notation for constant lists only, not some sort of gluing-things-together operation. So this, for instance: let L be {100, the turn count}; is not allowed, even though "the turn count" is a number: because it is a number that varies, the braces do not contain constants, and therefore this is not a list constant. 20.3. Saying lists of values Any list L can be said: let L1 be {2, 3, 5, 7, 11}; say L1; produces the text "2, 3, 5, 7 and 11" - unless we have "Use serial comma." set, in which case a comma appears after the 7. We also have the option of using the more formal notation:

say "[list of values in brace notation]"
This text substitution produces the list in the form of "{", then a comma-separated list, and then "}", which looks less like an English sentence but more mathematical. Example: "[list of people in brace notation]" might produce "{ yourself, Mr Darcy, Flashman }".
If we say a list of lists, then the individual entry lists are always printed in brace notation: the ordinary sentence way would be incomprehensible. Of course, the values in L1 are written out in number form because L1 is a list of numbers: we could alternatively try let L2 be {the piano, the music stand}; say L2; which produces "piano and music stand". Lists of objects can be said in two additional ways:

say "[list of objects with definite articles]"
This text substitution writes out the list in sentence form, adding the appropriate definite articles. Example: let L be {the piano, the music stand}; say "[L with definite articles]"; says "the piano and the music stand".

say "[list of objects with indefinite articles]"
This text substitution writes out the list in sentence form, adding the appropriate indefinite articles. Example: let L be {the piano, the music stand}; say "[L with definite articles]"; says "a piano and a music stand".
Example 414 (*): Oyster Wide Shut Replacing Inform's default printing of properties such as "(closed)", "(open and providing light)", etc., with our own, more flexible variation. 20.4. Testing and iterating over lists If L is a list, we can interrogate it to see whether it does or does not contain (at least one instance of) any compatible value V:

if (value) is listed in (list of values):
This condition is true if the given value, which must be of a compatible kind, is one of those in the list. For instance, if L is our list of the numbers 2, 3, 5, 7 and 11 then 5 is listed in it but 6 is not.

if (value) is not listed in (list of values):
This condition is true if the given value, which must be of a compatible kind, is not one of those in the list.
We can also repeat running through a list (just as we can with table rows). Thus:

repeat with (a name not so far used) running through (list of values):
This phrase causes the block of phrases following it to be repeated once for each item in the given list, storing that value in the named variable. (The variable exists only temporarily, within the repetition.) Example: let L be {2, 3, 5, 7, 11, 13, 17, 19}; repeat with prime running through L: ... If the list is empty, nothing happens: the "..." phrase(s) are never tried.
In the next sections, we shall see that it is possible to change, reorder and resize lists. But it's important never to change a list that's being repeated through. The following: let L1 be {1, 2, 3, 4}; repeat with n running through L1: remove n from L1; leaves L1 containing {2, 4}, since the removals from the list cause it to shuffle back even while we repeat through it - a bad, bad idea. 20.5. Building lists We have already seen "add... to...". This in fact comes in two forms:

add (value) to (list of values)
This phrase adds the given value to the end of the list. Example: let L be {60, 168}; add 360 to L; results in L being {60, 168, 360}. Note that the value is added even if it already occurs somewhere in L; this can be avoided with "if absent". So: add 168 to L, if absent; would do nothing - it is already there.

add (list of values) to (list of values)
This phrase adds the first list to the end of the second. Example: let L be {2, 3, 5, 7}; add {11, 13, 17, 19} to L; results in L being {2, 3, 5, 7, 11, 13, 17, 19}.
If we don't want to add new entries at the end, we can instead say where they should go:

add (value) at entry (number) in (list of values)
This phrase adds the given value so that it becomes the entry with that index number in the list. Example: let L be {1, 2, 3, 4, 8, 24}; add 12 at entry 6 in L; sets L to {1, 2, 3, 4, 8, 12, 24}. If there are N entries in L, then we can add at any of entries 1 up to N+1: adding at entry N+1 means adding at the end. The phrase option "if absent" makes the phrase do nothing if the value already exists anywhere in L.

add (list of values) at entry (number) in (list of values)
This phrase adds the first list to the second so that it begins at the given position. Example: let L be {1, 2, 3, 4}; add {4, 8, 12} at entry 3 in L; results in L being {1, 2, 4, 8, 12, 3, 4}.
A list is allowed to contain duplicates, and the order matters. For instance: let L be {2, 2, 3}; makes L into "2, 2 and 3". This is a different list to the one made by: let M be {2, 3, 2}; even though L and M have the same values, repeated the same number of times - for two lists to be equal, they must have the same kind of entry, the same number of entries, and the same entries in each position. We can also strike out values:

remove (value) from (list of values)
This phrase removes every instance of the given value from the list. Example: let L be {3, 1, 4, 1, 5, 9, 2, 6, 5, 3}; remove 1 from L; results in L being {3, 4, 5, 9, 2, 6, 5, 3}. Ordinarily "remove 7 from L" would produce a run-time problem, since L does not contain the value 7, but using the "if present" option lets us off this: the phrase then does nothing if L does not contain the value to be removed.

remove (list of values) from (list of values)
This phrase removes every instance of any value in the first list from the second. Example: let L be {3, 1, 4, 1, 5, 9, 2, 6, 5, 3}; remove {0, 2, 4, 6, 8} from L; results in L being {3, 1, 5, 9, 5, 3}. If both lists are large, this can be a slow process, and we might do better by sorting them and trying a more sophisticated method. But this is convenient for anything reasonable-sized.
Again, we can also remove from specific positions:

remove entry (number) from (list of values)
This phrase removes the entry at the given position, counting from 1 as the first entry. (Once it is removed, the other entries shuffle down.) Example: let L be {3, 1, 4, 1, 5, 9, 2, 6, 5, 3}; remove entry 3 from L; results in L being {3, 1, 1, 5, 9, 2, 6, 5, 3}.

remove entries (number) to (number) from (list of values)
This phrase removes the entries at the given range of positions, counting from 1 as the first entry. (Once they are removed, the other entries shuffle down.) Example: let L be {3, 1, 4, 1, 5, 9, 2, 6, 5, 3}; remove entries 3 to 6 from L; results in L being {3, 1, 2, 6, 5, 3}.
Example 415 (*): Robo 1 A robot which watches and records the player's actions, then tries to repeat them back in the same order when he is switched into play-back mode. 20.6. Lists of objects Lists can be made of values of any kind (including other lists), but lists of objects are especially useful. We could always make these "by hand": let L be {the pot plant, the foxglove}; But it is usually easier and clearer to use descriptions.

list of (description of values) ... value
This phrase produces the list of all values matching the given description. Inform will issue a problem message if the result would be an infinite list, or one which is impractical to test: for instance "list of even numbers" is not feasible.
While that works nicely for many kinds of value ("list of recurring scenes", say), it's particularly useful for objects: let L be the list of open containers; add the list of open doors to L; means that L now contains the open containers (if any) followed by the open doors (if any). Or, for example: let L be the list of things; remove the list of backdrops from L; makes a list of all non-backdrops. As mentioned above, lists of objects can be said in two additional ways: "[L with definite articles]" "[L with indefinite articles]" And as mentioned below, they can be sorted in property value order: sort L in P order; sort L in reverse P order; where P is any value property. In all other respects, lists of objects are no different to other lists. One special list of objects inside the command parser is worth mentioning. This is the "multiple object list", and is used in commands like this: >GET ALL foxglove: Taken. snake's head fritillary: Taken. After the command parser has decided what constitutes "ALL" (a process which can be influenced using the "deciding whether all includes" activity), it forms up a list and then runs through it, starting an action for each in turn. Here the list has two entries and Inform generates the actions "taking the foxglove" and then "taking the snake's head fritillary". For two technical reasons this isn't stored as a "list of objects that varies" - first because it needs to exist even in low-memory situations where we can't afford full list-processing, and second because there are times when changing it might be hazardous. Instead, two phrases are provided to read the list and to write it back:

multiple object list ... list of objects
This phrase produces the current multiple object list as a value. The list will be the collection of objects found to match a plural noun like ALL in the most recent command typed by the player. If there is no multiple object, say if the command was TAKE PEAR, the list will be empty: it won't be a list of size 1.

alter the multiple object list to (list of objects)
This phrase sets the multiple object list to the given value. The list is ordinarily the collection of objects found to match a plural noun like ALL in the most recent command typed by the player, but using this phrase at the right moment (before the "generate action rule" in the turn sequence rules takes effect).
Example 416 (*): What Makes You Tick Building a fishing pole from several component parts that the player might put together in any order. Example 417 (**): Formicidae Manipulating the order in which items are handled after TAKE ALL. 20.7. Lists of values matching a description The useful "list of ..." syntax can also be used to produce lists of the values matching a description, too. Thus: let L be the list of non-recurring scenes; let C be the list of colours; There is little to say here except for the usual warning that some kinds of value have a range which is too large to make this possible. For instance, Inform could not sensibly represent: let N be the list of even numbers; It would just be too large to hold. In general, if we can repeat through, or find the number of, values matching a description, then we can also use "list of" to bring them all together. See the chart of kinds of value in the Kinds index for a project for which kinds of value allow this. 20.8. Sorting, reversing and rotating lists Any list L can be reversed:

reverse (list of values)
This phrase puts the list in reverse order. The old entry 1 becomes the new last entry, and so on: reversing an empty list or a list containing only one entry leaves it unchanged. Example: let L be {11, 12, 14, 15, 16, 17}; reverse L; results in L being {17, 16, 15, 14, 12, 11}.
And any list can similarly be sorted:

sort (list of values)
This phrase puts the list into ascending order. Example: let L be {6 PM, 11:13 AM, 4:21 PM, 9:01 AM}; sort L; results in L being {9:01 AM, 11:13 AM, 4:21 PM, 6 PM}.

sort (list of values) in reverse order
This phrase puts the list into descending order. Example: let L be {6 PM, 11:13 AM, 4:21 PM, 9:01 AM}; sort L in reverse order; results in L being {6 PM, 4:21 PM, 11:13 AM, 9:01 AM}.

sort (list of values) in random order
This phrase puts the list into a uniformly random order, shuffling it as if it were a pack of cards. Example: let L be {1, 2, 3, 4, 5, 6}; sort L in random order; might result in L being {3, 1, 5, 6, 4, 2}. Or any of 719 other arrangements, including being left as it was.
Lists of objects can also be sorted in property value order. For instance,

sort (list of objects) in (property) order
This phrase puts the list into ascending order of the values of the given property for the items in the list; this is only allowed if all of those values do have the property in question. Example: let L be the list of people; sort L in carrying capacity order; would arrange people with weaklings first, titans last.

sort (list of objects) in reverse (property) order
This phrase puts the list into descending order of the values of the given property for the items in the list; this is only allowed if all of those values do have the property in question. Example: let L be the list of people; sort L in reverse carrying capacity order; would arrange people with titans first, weaklings last.
Rotating a list means moving all of its entries along by one place, and then moving the one on the end back to the start. For instance, if L is {1, 2, 3, 4}, then

rotate (list of values)
This phrase shuffles the entries of the list forwards (to the right) by one place, so that the 1st becomes 2nd, the 2nd becomes 3rd, and so on until the last, which becomes the new first entry. Example: let L be { "cow", "heifer", "bullock" }; rotate L; results in L being { "bullock", "cow", "heifer" }.

rotate (list of values) backwards
This phrase shuffles the entries of the list backwards (to the left) by one place, so that the 3rd becomes 2nd, the 2nd becomes 1st, and so on; the previous 1st entry becomes the new last entry. Example: let L be { "cow", "heifer", "bullock" }; rotate L backwards; results in L being { "heifer", "bullock", "cow"}. (This achieves the same effect as "reverse L; rotate L; reverse L;" but is a little faster, and a lot less effort to read.)
20.9. Accessing entries in a list The length of a list can change as values are added or removed, and can in principle be any number from 0 upwards. A list with 0 entries is empty. We can find the length with:

number of entries in/of (list of values) ... number
This phrase produces the number of positions in the list. Example: the number of entries in {1, 1, 1, 3, 1} is 5, even though there are only two genuinely different items in the list.
If the length is N then the entries are numbered from 1 (the front) to N (the back). These entries can be accessed directly by their numbers. For instance, entry 2 of L refers to the second entry of L: it can be used as a value, or changed, just as if it were a named variable. For instance, we could write: now entry 7 of L is "Spain"; say "The rain in [entry 7 of L] stays mainly in the plain."; which would (untruthfully) print "The rain in Spain stays mainly in the plain", but only if L had an entry 7 to make use of: if L were a list of 5 entries, say, then a run-time problem results. (And if L cannot hold text, a problem message means that we never get as far as run-time.) Because entries number from 1, this is always incorrect: entry 0 of L and if L is currently empty, then there is no entry which can be accessed, so that any use of "entry ... of L" would produce a run-time problem. There are programming languages in the world where accessing entry 100 in a 7-entry list automatically extends it to be 100 entries long: Inform is not one of them. But see the next section for how to change list lengths explicitly. Example 418 (***): Robo 2 A robot which watches and records the player's actions, then tries to repeat them back in the same order when he is switched into play-back mode. 20.10. Lengthening or shortening a list We can explicitly change the length of a list like so:

change (list of values) to have (number) entries/entry
This phrase alters the given list so that it now has exactly the number of entries given. Example: change L to have 21 entries; If L previously had more than 21 entries, they are thrown away (and lost forever); if L previously had fewer, then new entries are created, using the default value for whatever kind of value L holds. So extending a list of numbers will pad it out with 0s, but extending a list of texts will pad it out with the empty text "", and so on.
We can also write the slightly different phrases:

truncate (list of values) to (number) entries/entry
This phrase alters the given list so that it now has no more than the number of entries given. Example: truncate L to 8 entries; shortens L to length 8 if it is currently longer than that, trimming entries from the end, but would (for instance) leave a list of length 3 unchanged. Note that truncate L to 0 entries; empties it to { }, the list with nothing in.

truncate (list of values) to the first (number) entries/entry
This phrase alters the given list so that it now consists only of the initial part of the list with the given length. Example: truncate L to the first 4 entries; turns {1, 3, 5, 7, 9, 11} to {1, 3, 5, 7}.

truncate (list of values) to the last (number) entries/entry
This phrase alters the given list so that it now consists only of the final part of the list with the given length. Example: truncate L to the last 4 entries; turns {1, 3, 5, 7, 9, 11} to {5, 7, 9, 11}.
But we don't have to truncate: we can also -

extend (list of values) to (number) entries/entry
This phrase pads out the list with default values as needed so that it now has at least the given length. (If the list is already at least that length, nothing is done.) Example: extend L to 80 entries; lengthens L to length 80 if it is currently shorter than that.
For example, To check sorting (N - a number): let L be a list of numbers; extend L to N entries; repeat with X running from 1 to N: now entry X of L is X; say "L unrandomised is [L]."; sort L in random order; say "L randomised is [L]."; sort L; say "L in ascending order is [L]." builds a list of N numbers (initially all 0), fills it with the numbers 1, 2, 3, ..., N, then randomly reorders them, then sorts them back again, recovering the original order. The text produced by "check sorting 10" depends partly on chance but might for instance be: L unrandomised is 1, 2, 3, 4, 5, 6, 7, 8, 9 and 10. L randomised is 6, 2, 9, 3, 10, 1, 7, 4, 8 and 5. L in ascending order is 1, 2, 3, 4, 5, 6, 7, 8, 9 and 10. As with indexed text in the previous chapter, a project which needs really long lists should use the Glulx virtual machine - "check sorting 10000", for instance, would break the default memory environment on the Z-machine, which is very tight, but works fine (if not very rapidly) on Glulx. Example 419 (*): Leopard-skin A maze that the player can escape if he performs an exact sequence of actions. Example 420 (**): The Facts Were These Creating a variant GIVE action that lets the player give multiple objects simultaneously with commands like GIVE ALL TO ATTENDANT or GIVE THREE DOLLARS TO ATTENDANT or GIVE PIE AND HAT TO ATTENDANT. The attendant accepts the gifts only if their total combined value matches some minimum amount. 20.11. Variations: arrays, logs, queues, stacks, sets, sieves and rings Lists are highly adaptable, and many other collection-like constructions can be made using them. This section introduces no new material, but simply suggests some of the variations which are possible. 1. The traditional computing term array means a list of values accessed by their entry numbers, often used in mathematical computations. The difference between an array and a list is mostly one of attitude, but usually arrays are fixed in length whereas lists can expand or contract. 2. A log is a list which records the most recently arrived values, but does not allow itself to grow indefinitely. In the following, which remembers the seven most recently taken items, new values arrive at the end while old ones eventually disappear from the front: The most-recently-taken list is a list of objects that varies. Carry out taking something (called the item): truncate the most-recently-taken list to the last 6 entries; add the item to the most-recently-taken list. After taking: say "Taken. (So, your recent acquisitions: [most-recently-taken list].)" Note that the most-recently-taken list begins play as the empty list, grows as the first few items are taken, but then stabilises at length 7 thereafter. If we need to remember recent history, but only recent history, then a log is better than a list which can grow indefinitely, because there is no risk of speed reduction or memory exhaustion in a very long game. 3. A queue is a list of values which are waiting for attention. New values join at the back, while those being dealt with are removed from the front (whereupon the whole queue moves up one). An empty queue means that nobody is waiting for attention: but there is, in principle, no upper limit to the size of a queue, as anyone who has tried to make a couchette reservation at Roma Termini will know. Queues typically form when two independent processes are at work, but going at different or variable speeds. An empty queue looks just like any other list: The queue is a list of objects that varies. (Invariably people, in fact, but lists can only be of kinds of value: so, "list of objects".) Once we identify a "new customer", we can join him to the queue thus: add the new customer to the queue; The process of serving the customers needs to make sure there is actually somebody waiting in the queue before it does anything: Every turn when the number of entries in the queue is not 0: let the next customer be entry 1 of the queue; say "[The next customer] is served and leaves."; remove entry 1 from the queue. Of course queues can also be constructed which empty from other positions, rather than the front: or we could make what computer scientists sometimes call a deque, a "double-ended queue" where new values arrive at both ends. 4. A stack is like a queue except that values arrive at, and are removed from, the same end. Stacks are slightly faster if the active end is the back rather than the front, though this will only be noticeable if they grow quite large. To put a value V onto a stack S (which is known as "pushing") is simple: add V to S; And to remove a value from the top of the stack (which is known as "pulling"): let N be the number of entries in S; let V be entry N of S; remove entry N of S; Note that the middle line, accessing entry N, will fail if N = 0, that is, if the stack is empty: Inform's list routines will produce a run-time problem message. Stacks are useful if some long-term process is constantly being interrupted by newer and more urgent demands, but they can also be used in planning. If a character has a long-term goal, which needs various short-term goals to be achieved along the way, then a stack can represent the goals currently being pursued. The top of the stack represents what the character is trying to achieve now. If the character realises that it needs to achieve something else first, we put that new goal onto the top of the stack, and it becomes the new current goal. When the character completes a task, it can be removed, and we can go back to trying to finish whatever is now on top. When the stack is empty, the character has achieved the original goal. 5. Notoriously, set has 464 distinct meanings in the Oxford English Dictionary, making it the single most ambiguous word in the language. Here we mean not the home of a badger or the Egyptian god of the desert, but the mathematical sense: a collection of values (sometimes called "elements") without duplicates, and which is normally written in brace notation and in some natural order for the reader's convenience. The trick here is to maintain the principle that, at all times, our list is sorted in order and contains no duplicates. To provide an example, we start with two sets of numbers: let S be {2, 4, 8, 16, 32, 64}; let T be {2, 4, 6, 10}; Here we add an element to T: add 8 to T, if absent; sort T; The "if absent" clause ensures that no duplicate can occur, and by sorting T afterwards, we maintain the principle that a set must remain in order - so T is now {2, 4, 6, 8, 10}, not {2, 4, 6, 10, 8}. (Inform's sorting algorithm is fast on nearly-sorted lists, so frequent sorting is not as inefficient as it might look.) We next take the union of T and S, that is, the set containing everything which is in either or both: let U be S; add T to U, if absent; sort U; This makes U = {2, 4, 6, 8, 10, 16, 32, 64}, and once again no duplicates occur and we preserve the sorting. The intersection of T and S, the set of elements in both of them, is a little trickier: let I be T; repeat with the element running through T: if the element is not listed in S, remove the element from I. (Faster methods could be devised which exploit the sortedness of T and S, but are not worth it for shortish lists.) This produces I = {2, 4, 8}. Lastly, we can form the set difference, consisting of those elements which are in S but not in T: let D be S; remove T from D, if present; Here, as with intersection, since all we do is to strike out unwanted elements, the surviving ones remain in order and there is no need to sort when we are finished. This produces D = {16, 32, 64}. 6. A sieve is used to make a complicated choice where there are many constraints, by ruling out impossible cases to see what is left. The term derives from the kitchen utensil (for sieving fine grains of flour), but via the name of the "sieve of Eratosthenes", an ancient Greek method for determining the prime numbers. Using a sieve is much like using a set, and the difference is mainly one of outlook - we are interested in what does not belong, rather than what does. 7. A ring is not so much a row of values, more a circle, with the last and first entries thought of as adjacent. One position is usually thought of as special, and is the place where new items are added: this may as well be entry 1. For instance, to add "new item" to the ring: add the item at entry 1 in the ring; To set "item" to the frontmost value and extract it from the ring: let the item be entry 1 of the ring; remove entry 1 from the ring; And we can rotate the ring in either direction, making a different entry the new entry 1 and therefore the new frontmost value: rotate the ring; rotate the ring backwards; Example 421 (*): Eyes, Fingers, Toes A safe with a multi-number combination, meant to be dialed over multiple turns, is implemented using a log of the last three numbers dialed. The log can then be compared to the safe's correct combination. Example 422 (*): The Fibonacci Sequence The modest Leonardo Fibonacci of Pisa will be only too happy to construct his sequence on request, using an array. Example 423 (*): I Didn't Come All The Way From Great Portland Street In this fiendishly difficult puzzle, which may perhaps owe some inspiration to a certain BBC Radio panel game (1967-), a list is used as a set of actions to help enforce the rule that the player must keep going for ten turns without hesitation, repetition, or deviating from the subject on the card. Example 424 (*): Lugubrious Pete's Delicatessen In this evocation of supermarket deli counter life, a list is used as a queue to keep track of who is waiting to be served. Example 425 (*): Sieve of Eratosthenes The haughty Eratosthenes of Cyrene will nevertheless consent to sieve prime numbers on request. Example 426 (*): Your Mother Doesn't Work Here Your hard-working mother uses a list as a stack: urgent tasks are added to the end of the list, interrupting longer-term plans. Example 427 (*): Circle of Misery Retrieving items from an airport luggage carousel is such fun, how can we resist simulating it, using a list as a ring buffer? Chapter 21: Advanced Phrases 21.1. A review of kinds Most, if not quite all, Inform constructions are values - sometimes openly so, sometimes not. In this book, we haven't gone out of our way to make that point, because there was no real need to do so. It's possible to make heavy use of rulebooks and write large-scale Inform projects without ever needing to use a rulebook's name as a value in its own right, for example. But if we want to create sophisticated extensions to Inform, or to use modern techniques such as functional and generic programming, we need to be fluent in the language of kinds. Inform's language of kinds has four ingredients: base kinds, constructions, kind variables and kinds of kinds. 1. Base kinds. Inform provides the following base kinds for values: object, number, time, truth state, text, indexed text, snippet, Unicode character, stored action, scene, table name, equation name, use option, action name, figure name, sound name, external file And Inform allows us to create new base kinds either by making more specialised kinds of object: A geographical layout is a kind of object. A marmoset is a kind of animal. Or by making new enumerations or arithmetical kinds: Distance is a kind of value. 10km specifies a distance. Colour is a kind of value. Red, green and blue are colours. 2. Constructions. These are ways to make new kinds from existing ones. The construction most often used is "list of...". For any kind K, there is a kind called list of K. So the range of possible kinds in Inform is actually infinite, because: number list of numbers list of lists of numbers list of lists of lists of numbers ... are all different from each other. Inform currently has nine constructions, and does not (yet) provide a way for us to create new ones. Here they are: list of K description of K relation of K to L K based rule producing L K based rulebook producing L activity on K phrase K -> L K valued property K valued table column Some of these have appeared in previous chapters, but in abbreviated form. For example, "rulebook" abbreviates "action based rulebook producing nothing", and "either/or property" is a synonym for "truth state valued property". The kinds of descriptions and phrases haven't been covered yet, but are coming up in the sections following. These constructions can of course be combined: phrase (relation of numbers to colours, number) -> list of colours Brackets can be used to clarify matters: phrase (phrase number -> (phrase number -> number)) -> nothing Nothing will make that a simple idea, but it's unambiguous and can be puzzled out with practice. 3. Variables. In a way, that's everything: there are just base kinds and constructions on them, and those construct every possible kind in Inform. But the language we use to describe kinds is larger than that, because it allows us to describe many kinds at once, in the same way that Inform reads the word "something" as applying to many objects at once, not as a single object. Kind variables will be covered later in the chapter, but the idea is that: To hunt for (needle - value of kind K) in (haystack - list of Ks): ... allows us to describe the kinds acceptable in a phrase so that a wide range of possibilities are allowed. The above matches both: hunt for 4 in { 2, 3, 4, 5 }; hunt for "fish" in { "lemon sauce", "fish", "garden peas" }; The letter K in the definition stood for any kind; in the first use of "hunt" here, K turned out to be "number", and in the second it was "text". On the other hand Inform would reject: hunt for 4 in { containment relation, support relation }; because there is no kind K which can make this match the definition. There are potentially 26 kind variables, A to Z, though it's customary to use them in the order K, L, M, ..., and it's very rare to need more than two at a time. 4. Kinds of kind. Inform understands several names which look as if they are kinds, but actually aren't: value, arithmetic value, enumerated value, sayable value (Again, these are built in to Inform.) They are not kinds because they're just too loose and vague. Instead, they can be used in phrase definitions to match against multiple possibilities: To announce (X - sayable value): say "I declare that [X] has arrived." This makes "announce X" work for any value X which can be said. All the same, "sayable value" is not a kind. It could never be safe for this to be the kind of a variable, because Inform would never know what could be done with the contents (except that it could be printed out). 5. Secret inner workings. There isn't a fifth ingredient, but if there were, it would be a handful of names used in matching some of the core built-in phrases of Inform which have so-called inline I6 definitions. These are not intended for anyone else to use, and are just an internal convenience; they aren't publically documented and might change without notice. They don't describe kinds at all, because they tell the matcher to look for something else instead. For instance, there's one called "condition", which means "match a condition rather than a value". They appear in red ink in the Phrasebook index. 21.2. Descriptions as values In the chapter on Descriptions, we saw that a description can be any source text which describes one or more objects: it might be as simple as "the Corn Market", or as complicated as "open containers which are in dark rooms". More or less the only restriction is that it must be unambiguous as to what counts and what does not: "three containers" is ambiguous as a description because it does not say which three. We've now seen several interesting tricks with descriptions. In fact, if D is a description, then say "You gaze mournfully at [the list of D]."; let the tally be the number of D; let the surprise prize be a random D; repeat with item running through D: ... are all standard things to do. These examples make it look as if it must be possible to define phrases which act on descriptions, and in fact it is, because a description can be a value in itself. For example, even numbers open containers which are in dark rooms are values of kind "description of numbers" and "description of objects" respectively. In general, if K is any kind then "description of K" is also a kind. Here is how we might make use of that: To enumerate (collection - a description of objects): repeat with the item running through the collection: say "-- [The item]." This makes "enumerate lighted rooms" run off a list of lighted rooms in a textual format different from the standard one produced by "say the list of lighted rooms". Inside the definition, "collection" can be used wherever a description might be used: here, for instance, we use it as the range for the repeat loop. (That's only possible because the range is limited in size: Inform wouldn't have allowed us to range through, say, all texts.) Purely as a convenience, we can also write "member of" or "members of" in this context. For instance, in the enumerate definition, it would have been just as good to write "...running through the members of the collection..." in the repeat. (Similarly, we could write "number of members of the collection" or "a random member of the collection", which looks grammatically tidier than writing "number of the collection" or "random of the collection" - though in fact both of these do work.) Finally, it's sometimes useful in an abstract situation to test

if (value) matches (description of values):
This condition is true if the value matches the description; the kinds must be compatible, or Inform will issue a problem message. There is no point using this for cases where the description is given explicitly: if 4 matches even numbers, ... because it is easier to write just: if 4 is an even number, ... So this condition is only useful when the description is stored in some variable, and its identity is not known.
Example 428 (*): Curare A phrase that chooses and names the least-recently selected item from the collection given, allowing the text to cycle semi-randomly through a group of objects. 21.3. Phrases as values Given any two kinds K and L, the kind "phrase K -> L" is now a kind. (This is meant to look like a mathematical function arrow.) For example, the phrase defined by To decide which number is the square of (N - a number): ... has the kind "phrase number -> number". Brackets and commas are used if the phrase combines several values, so To decide which indexed text is (T - text) repeated (N - a number) times: ... has the kind "phrase (text, number) -> indexed text". The word "nothing" is used if there are no values in, or no value out - thus To decide which number is the magic target: ... has kind "phrase nothing -> number", and To dig (eastward - length) by (northward - length): ... has the kind "phrase (length, length) -> nothing". But how are we to get at these values? The answer is that we need to give a phrase a name in order to do so. For example: To decide what number is double (N - a number) (this is doubling): decide on N plus N. This is the same syntax used to name rules, and the idea is the same. If we try "showme doubling", the result is phrase number -> number: doubling The main thing we want to do with a phrase is to apply it. So: showme doubling applied to 2; produces "doubling applied to 2" = number: 4 There are versions of "applied to" for phrases applied to 0 to 3 values:

(phrase nothing -> value) applied ... value
This phrase produces the result of applying the given phrase, which must be one which takes no values itself.

(phrase value -> value) applied to (value) ... value
This phrase produces the result of applying the given phrase, which must be one which takes one value itself.

(phrase (value, value) -> value) applied to (value) and (value) ... value
This phrase produces the result of applying the given phrase, which must be one which takes two values itself.

(phrase (value, value, value) -> value) applied to (value) and (value) and (value) ... value
This phrase produces the result of applying the given phrase, which must be one which takes three values itself.
So for example: F applied F applied to V F applied to V and W F applied to V and W and X For phrases which do not produce a value, we use "apply":

apply (phrase nothing -> nothing)
This phrase causes the given phrase to be applied. It must be one which takes no values itself.

apply (phrase value -> nothing) to (value)
This phrase causes the given phrase to be applied. It must be one which takes one value itself.

apply (phrase (value, value) -> nothing) to (value) and (value)
This phrase causes the given phrase to be applied. It must be one which takes two values itself.

apply (phrase (value, value, value) -> nothing) to (value) and (value) and (value)
This phrase causes the given phrase to be applied. It must be one which takes three values itself.
Thus: apply F; apply F to V; apply F to V and W; apply F to V and W and X; 21.4. Default values for phrase kinds The default value for "phrase K -> nothing" is a phrase which does nothing. For example, if we write: let S be a phrase numbers -> nothing; then S is created holding the default phrase numbers -> nothing, and if we then try it out with: apply S to 17; we will indeed find that nothing happens. The default value for "phrase K -> L" is a phrase which, no matter what value of K it applies to, always produces the default value of L. (It's a sort of equivalent of the zero function in mathematics - indeed that's exactly what it is, if L is "number".) So: let Q be a phrase numbers -> times; showme Q; showme Q applied to 4; showme Q applied to -7; produces: "q" = phrase number -> time: default value of phrase number -> time "q applied to 4" = time: 9:00 am "q applied to -7" = time: 9:00 am Here Q is set to the default phrase because we didn't give it any other value; it has the name we might expect ("default value of phrase number -> time") and it works as advertised, producing 9:00 am no matter what number is fed in. More ambitiously, and supposing that we have a kind called "colour" whose first possible value is "red": let R be a phrase numbers -> (phrase numbers -> colours); showme R; showme R applied to 3; showme (R applied to 3) applied to 2; produces: "r" = phrase number -> (phrase number -> colour): default value of phrase number -> (phrase number -> colour) "r applied to 3" = phrase number -> colour: default value of phrase number -> colour "( r applied to 3 ) applied to 2" = colour: red 21.5. Map, filter and reduce When a mass of computations has to be done, the traditional approach is to work through them in a "repeat" loop. One modern alternative, growing in popularity, is to form a list of inputs; then apply the same computation to each input in turn to form a list of results (this is called "mapping"); throw out any bad or unwanted results ("filtering"); and then combine the surviving results into a single composite answer ("reducing", though some programming languages call this "folding" or "accumulation"; it's a much-reinvented idea). Inform provides all three of these fundamental list-processing operations. There is no special term for a "map", because Inform treats it as another case of "applied to".

(phrase value -> value) applied to (list of values) ... value
This phrase takes the list, applies the phrase to each entry in the list, and forms a new list of the result. Example: To decide what number is double (N - a number) (this is doubling): decide on N plus N. Then "doubling applied to 2" produces 4, by the simpler definition of "applied to", but also: doubling applied to {2, 3, 4} produces the list {4, 6, 8}.
More divertingly, suppose we define: To decide what indexed text is the longhand form of (N - a number) (this is spelling out): decide on "[N in words]". To decide what indexed text is the consonant form of (T - indexed text) (this is txtng): replace the regular expression "" in T with ""; decide on T. Then we can write a chain of three maps in succession: txtng applied to spelling out applied to doubling applied to {3, 8, 4, 19, 7} to produce the value {"sx", "sxtn", "ght", "thrty-ght", "frtn"}. Next, filtering. Here we make use of descriptions, in order to say what values will be allowed through the filter. So:

filter to (description of values) of (list of values) ... value
This phrase produces a new list which is a thinner version of the one given, so that it contains only those values which match the description given. Example: filter to even numbers of {3, 8, 4, 19, 7} produces {8, 4}, with the values 3, 19, and 7 failing to make it through. A sufficiently fine filter may well thin out a list to a single entry, or even no entries at all, but the result is always a list.
To get the full effect of filtering, we probably need to define an adjective or two. For example: Definition: an indexed text (called T) is lengthy if the number of characters in it is greater than 6. We can then write: filter to lengthy indexed texts of spelling out applied to {15, 2, 20, 29, -4} which produces {"fifteen", "twenty-nine", "minus four"}. Lastly, reduction. In order to combine a whole list of values, we need a phrase to combine any two. Here are some samples: To decide what number is the larger of (N - number) and (M - number) (this is maximizing): if N > M, decide on N; decide on M. To decide what indexed text is the concatenation of (X - indexed text) and (Y - indexed text) (this is concatenation): decide on "[X][Y]". And here are some sample reductions: let X be the maximization reduction of {3, 8, 4, 19, 7}; let Y be the concatenation reduction of txtng applied to spelling out applied to doubling applied to {3, 8, 4, 19, 7}; sets X to 19, the highest of the values, and Z to the indexed text "sxsxtnghtthrty-ghtfrtn". In each case a list has been reduced to a single value which somehow combines the contents.

(phrase (value, value) -> value) reduction of (list of values) ... value
This phrase works through the list and accumulates the values in it, using the phrase supplied. Example: if we have To decide what number is the sum of (N - number) and (M - number) (this is summing): decide on N + M. then the summing reduction of {3, 8, 4, 19, 7} is the number 41, obtained by (((3 + 8) + 4) + 19) + 7 so that the summing phrase has been used four times.
Is map/filter/reduce always a good idea? Devotees point out that almost any computation can be thought of in this way, and in systems where the work has to be distributed around multiple processors it can be a very powerful tool. (There are programming languages without loops where it's essentially the only tool.) At its best, it reads very elegantly: one assembles all of the tools needed - definitions of doubling, lengthy, spelling out, concatenation and so on - and then each actual task is expressed in a single line at the end. On the other hand, there are also times when this is a needlessly complicated disguise for what could more easily be done with a "repeat" loop, and also more efficiently since assembling and dismantling lists in memory does take some overhead time. So these list operations are not a panacea, but it's good to have them available. 21.6. Generic phrases The following looks quite innocent: To say (V - value) twice: say "[V]. [V], I say!" It's clear at a glance what this is intended to do, but at a second glance things aren't so straightforward. "Value" is not itself a kind - it's too big and unspecific. For instance, if we were to allow a variable to be just "a value", we could freely set it to 12 one minute and to "dahlias" the next, and such a variable would be dangerous since we would never know what could safely be done with its contents. A phrase like this one is called "generic", because it's not so much a single, actual phrase as a recipe to make phrases. (Inform automatically works out which kinds we need the phrase for, and creates a version of the phrase for those kinds.) So "value" is not a kind, but a kind of kind. Inform has several of these: value, arithmetic value, enumerated value, sayable value These act as ways to say "a value of any kind matching this can go here". For example, "value" is a way to say "any kind at all"; "arithmetic value" is any kind which arithmetic can be performed on (any kind with the little calculator icon in the Kinds index); and so on. If we write: To double (V - arithmetic value): say "[V times 2]." the restriction to "arithmetic value" means that although "double 3", "double 6 kg", etc., would be matched, "double the Entire Game" would not - you can't perform arithmetic on scenes. Similarly, it would have been tidier to write: To say (V - sayable value) twice: say "[V]. [V], I say!" because then Inform will make it clearer why "say X twice" won't work if X is one of those rare values which it can't say (an activity, for instance). The Kinds index shows which kinds match against which of these "kinds of kind". For instance, it shows that "time" Matches: value, arithmetic value, sayable value which means that time is something we can do arithmetic on, and can say. 21.7. Kind variables The examples of generic phrases in the previous section were really only toy examples. Suppose we want a phrase which will take any arithmetic value and triple it. We could do something like this: To triple (V - arithmetic value): say "[V times 3]." But this only prints the answer. Suppose we want to be given the value back, instead: how can we write the phrase? The trouble is that, not knowing the kind of V, we can't say what kind will be produced. We need a way of saying "the same kind comes out as went in". Inform expresses that using kind variables: To decide which K is triple (original - arithmetic value of kind K): decide on 3 times the original. Here, K stands for any kind which matches "arithmetic value". Inform supports exactly 26 of these symbols, which are written A to Z, but it's customary to use K and L. (They can be written in the plural if we like: e.g., "list of Ks". But they must always use a capital letter: "list of k" is not allowed.) Each symbol we use has to be declared in exactly one of the bracketed ingredients for the phrase - here, the declaration is "arithmetic value of kind K". That creates K and says that it has to be arithmetic; if we'd just said "value of kind K", it could have been anything. (Alternatively, we could use any of the kinds of kind in the previous section.) For a more ambitious example, here is one way to define the mapping operation described earlier in the chapter: To decide what list of L is (function - phrase K -> value of kind L) applied to (original list - list of values of kind K): let the result be a list of Ls; repeat with item running through the original list: let the mapped item be the function applied to the item; add the mapped item to the result; decide on the result. Here we need two symbols to explain the complicated way that the values going in and out have to match up to each other. Note also the way that the temporary variable "result" is created: let the result be a list of Ls; Ordinarily, of course, "L" is not a kind. But within the body of a phrase definition, it means whatever kind L matched against. When a symbol occurs several times in the same definition, subtle differences can arise according to which appearance is the declaration. These are not quite the same: To hunt for (V - value of kind K) in (L - list of Ks): ... To hunt for (V - K) in (L - list of values of kind K): ... Consider: let T be "[location]" in title case; hunt for T in {"Greater London", "Greater Basildon"}; Here T is an indexed text, but the list is of texts; and a text can be used in place of an indexed text, but not vice versa. This will match the first definition, because K is set to "indexed text", but it won't match the second, where K is set to "text". 21.8. Matching the names of kinds Sometimes a phrase needs to know what kind it's to work on, but isn't going to be given any particular value of it. For example: To assay (name of kind of value K): repeat with item running through Ks: say "There's [item]."; say "But the default is [default value of K]."; Note that there's no hyphen, and no name for the bracketed token - it only sets K. We can then have, say: assay colours; assay vehicles; But "assay texts" would throw a problem message, because we can't repeat through all possible texts. For a different reason, assay open doors; would not be allowed - "open doors" is a description which applies to some doors and not others; it isn't a kind. It would make no sense to talk about "default value of open door", for example. 21.9. In what order? Recall the definition: To slam shut (box - an open container): say "With great panache, you slam shut [the box].". Suppose we then try to "slam shut the wall safe" at a time during play when the wall safe is already closed. An error message will then be printed during play, since there must be a mistake in the design. The combination of checking both when Inform builds the story file and then continuously when the story file is played guarantees that, in all cases, a varying item such as "box" in the definition of "To slam shut (box - open container)" always satisfies the condition laid down. Instead suppose we also have the following definition: To slam shut (box - a container): say "You are unable to slam shut [the box], which is already closed.". We now have two definitions of "slam shut". Sometimes the box it's applied to will be closed, in which case only the second definition fits, and will be the one used. But if the box is open, both definitions fit. Which will happen? The rule is: 1. A narrower condition takes precedence over a broader one; 2. If neither condition is narrower than the other, then whichever phrase was defined later in the source code is the one taking precedence; 3. Except that if the phrase is being used in the definition of phrase P, then P is always last in precedence order, so that recursion is always the very last possibility considered. This allows more specific or later definitions to make use of less specific or earlier ones in a natural way. Rule 1 ensures that a definition involving "open container" takes priority over one which merely involves "container", for instance. And therefore when the box is open, it's the more specific phrase to do with open containers which is invoked: so, with great panache, the box is slammed shut. On the other hand, neither of these patterns is narrower than the other: To describe (something - transparent): ... To describe (something - container): ... Some containers are transparent, some not; some transparent things are containers, some not. Rule 1 therefore does not apply, so it is the later of the two phrases which takes effect. 21.10. Ambiguities Another possible ambiguity occurs when a phrase might match two lexically different possibilities using the same words. say the dishcloth; could be construed as a usage of either of these cases: say the (something - a thing) say (something - a thing) These of course have different effects - one produces the name with a definite article, the other just the name, so the difference is important. The rule here is that whichever possibility contains the most words, in this case "say the (...)", takes precedence, because it's assumed to be a more specific form of the less wordy version. Chapter 22: Figures, Sounds and Files 22.1. Beyond text In this chapter, we explore a number of ways to go beyond the traditional text-only, one-story-file-only model for IF. These relatively exotic features are more demanding of the interpreter which a player uses than a plain text story file would be. They can only be used if the project is being compiled to the Glulx story file format (see the Settings panel for the project), and even then, the player will need to have a good Glulx interpreter - one which is reasonably up to date and well-written, that is - to be sure of everything working as intended. 22.2. How IF views pictures Looking around a bookshop, perhaps half of all the books published have illustrations. The proportion may be lower for novels, but if we count maps or other occasional diagrams, even the fiction section turns out to be surprisingly pictorial. Illustrations do not suit every book, but they are an option we would like to have available. In the cultural history of IF, graphics in text adventures have sometimes been looked at with suspicion. Mostly this is because attempts in the 1980s were not very successful, because computer graphics were so poor then (by modern standards). It may be that some people also felt that the takeover of computer games by graphical interfaces was the death knell of IF. But pictures are now rendered in superb quality by computers, and the death of IF turned out to be an exaggeration, so it is time to move on. Whether to have illustrations ought to be an artistic choice, like whether to include a romantic sub-plot or how much of the back story is revealed. But there are practical considerations too. The most successful illustrated books are those whose pictures are well-chosen, have a sense of design to them, and above all are consistent. Consider how much worse off Winnie the Pooh would have been if a selection of random teddy-bear drawings had been used, instead of E. H. Shepherd's beautifully conceived world; or a cookery book in which the recipes are all photographed at different distances and light levels. IF writers may want to look for collaborators with a visual eye, just as most novelists do not draw their own illustrations. Another consideration is that displaying images is more complicated for computers than displaying text. Not all devices can show pictures (consider handheld gadgets) and if they do, they may use different colour ranges or resolutions. So IF with pictures is always just a bit less portable than IF without, and because of that we must next look again at IF story file formats. 22.3. Virtual machines and story file formats Back in Chapter 2, we saw that the Settings panel allows any given Inform project to be produced in one of four possible story file formats. Recall that story files are the released IF works: what the player sees. The source text, the Skein, and so on are not part of this. Although those four possible formats were introduced in Chapter 2, they have not been mentioned since, because almost everything in Inform will work fine on any of the possibilities. However, once we go beyond text and into images, they begin to behave differently. A story file is not like a word-processed document, or a photograph. There are many rival formats for these - for instance, an image on a web page might be in JPEG or PNG format, among many others - but basically they are simple things for the reader to look at, and see everything in one go. An IF story file is more complicated, because the "reader" reacts to it, types in to it, is surprised by it, never quite knows what might happen next. A story file is in fact a computer program in its own right, but not a program like iTunes or Firefox which runs on a typical home or business computer. Instead it is a program for an imaginary computer, called a "virtual machine" or "VM". This has a design ideally suited to IF, and it would be the perfect IF player's computer if only it actually existed. Because it doesn't, the player instead runs an "interpreter" program like Windows Glulxe or Zoom or Spatterlight - and this one is a program like iTunes or Firefox - and the interpreter acts as a middle-man. It creates a software version of the virtual machine, and then runs the IF story file on that VM. This sounds slow and impractical, but in fact it works well, and is also much safer since programs on the VM are not allowed to touch the real computer - so they cannot at all easily contain viruses or other malware. (In theory a malicious story file might try to exploit a bug in one of the various VM implementations in use, just as malicious image files have been used to attack bugs in web browsers, but this has never in practice happened. Nothing can be absolutely safe, but a story file belongs in the "mostly harmless" category of files - like images - rather than the "how far do you trust this person?" category - like programs.) The different formats of story file are programs for different virtual machines. Just as Windows and Mac OS X offer basically similar services to the user but are very different in appearance and their workings, so the different VMs are quite different. Some can display pictures, others not. 22.4. Gathering the figures Inform provides basic support for displaying pictures and leaves more exotic effects for Extensions to provide. But either way, for reasons explained in the previous section, we can only have pictures if the Settings for the project are set to the Glulx story file format. Inform calls these pictures "figures", following the usual Inform analogy with books. We will think of our work of IF as being like a mostly textual book which in broken up with illustrations here and there - Figure 1, Figure 2, and so on. These might be used to mark each new chapter of the plot, or each new location: whatever the author would like. So the first thing we need to do is decide when pictures should appear. The second thing to do is to get hold of the pictures we want to use. These might be photographs, or artwork, or diagrams: anything, really, but we will need them to be in either JPEG or PNG format. Inform does not itself try to be an image editor, or an artwork program - there are many such programs already which do these things much better than Inform could. The pictures then need to be put in a special place where Inform can reach them. Suppose the Inform project is called Example.inform. Then we need to create a folder alongside it called "Example Materials", and create a further folder inside that called "Figures". The actual images go inside "Figures". So we might then have files like so: Example.inform Example Materials Figures Woodlands.png Blackberry.jpg Red Admiral Butterfly.png The Materials folder for an Inform work will turn out to have many other uses in the chapter on Publishing, and will be explained further there. 22.5. Declaring and previewing the figures Inside Inform, the source text for a project always tries to avoid talking about filenames - we need a better way to refer to the individual figures. We do this by declaring each figure with a sentence like the following examples: Figure of Woodlands is the file "Woodlands.png". Figure 2 is the file "Red Admiral Butterfly.png". Figure names can consist of any text provided that text starts with the word "Figure". So "Figure 3 - Woodlands", for instance, or even "Figure W" would have been just as good as "Figure of Woodlands". Books tend to number figures, but then, in a book the order in which they appear is known in advance - which might not be true in IF. The file names must be exactly those used in the Figures folder. We need not declare every image kept there, but those we don't declare - remember Blackberry.jpg? - cannot be displayed. We can preview the stock of figures by going to the table of figures in the Contents index for a project (once the project has been built, that is, so that its index is up to date). This preview shows thumbnail forms of the pictures, the names, the formats and the image sizes in pixels. A warning triangle is shown for any images in the wrong format, or which are missing from the Figures folder. 22.6. Displaying the figures Inform's basic picture support simply allows figures to be shown at particular times. Once seen, they scroll away, just as text does once it has been printed. These pictures are really part of the stream of narrative. (If we would like icons or other images to be permanently present on screen, and divide the screen up in pictorial ways to achieve interesting layouts, we need to use special extensions to access Glulx's more exotic features.) Displaying a picture is therefore like printing some text. Rather than say "The woodlands stretch from here to the horizon."; we would use:

display (figure name)
This phrase causes the figure to be displayed in the centre of the screen visible to the player. If the option "one time only" is used, it will have no effect if the figure has been displayed before. Example: display the Figure of Woodlands;
Once again, note that the "display" phrase does nothing unless the Settings for the project are set to the Glulx story file format. When a Glulx work is released as a blorb (the default setting for the way releases occur: see the chapter on Publishing), all the images used are automatically included. 22.7. Recorded sounds Inform also supports the playing back of recorded sounds, which might be anything from a three-second sound effect for a creaking door to an epic orchestral symphony. Sound support is very newly added to the system and work is still in progress. In particular, sounds are not played by Inform for OS X (although it does produce valid blorbed Glulx story files), though they should be audible from within the Inform application for Windows. Once again, only Glulx-based works can incorporate sound effects, and we must be prepared for the fact that not all interpreters will be able to play them back. We must also bear in mind that a sound recording is a large pile of bits, and that adding any kind of sounds will greatly increase the size of the Blorb file for the released Glulx story file. The sound files provided must have one of two formats: AIFF or Ogg Vorbis. AIFF is a traditional format in the recording industry, though it is more familiar to Mac OS X users than Windows users. It is uncompressed, giving what can be excellent audio quality, but at the cost of sometimes enormous file sizes - perhaps as much as 10 MB per minute, though this can be greatly reduced by lowering the sampling frequency, and halved again by dropping from stereo to mono. Except for very short sound effects, we recommend using Ogg Vorbis instead. This is a compressed format whose file sizes will typically be more like 1 MB per minute. Inform uses Ogg Vorbis as the only format safe from licencing and patent disputes. (We would very much have liked to provide MP3 support, but this is no longer legally possible for free software.) Support for Ogg Vorbis is not built in to either Windows or Mac OS X, and any sound recording you make will probably have to be made first to another format (perhaps AIFF or WAV), and then converted. See www.vorbis.com for encoding software which can convert from other sound formats to Vorbis. Lastly, it must be remembered that recording industry bodies are very hostile to established copyright law covering fair use, parody, quotation of insubstantial passages, etc., when it comes to mixing or using commercially released music. They are well-resourced and highly litigious. If you use sound effects not originated by yourself, you do so at your own risk, even if what you do is perfectly legal on any reading of the statutes. 22.8. Declaring and playing back sounds Sound effects are accommodated on the same basis as illustrations. The relevant media files need to be placed in a subfolder of the project's Materials folder, but this time called Sounds rather than Figures, so for instance: Example.inform Example Materials Figures Woodlands.png Blackberry.jpg Red Admiral Butterfly.png Sounds Rustling leaves.ogg Again, these must be declared in the source text: Sound of rustling leaves is the file "Rustling leaves.ogg". And they can be played using a special phrase:

play (sound name)
This phrase causes the sound effect to be played. If the option "one time only" is used, it will have no effect if the sound effect has been played before. Example: play the sound of rustling leaves;
22.9. Some technicalities about figures and sounds (i) Names for figures, such as "Figure of Woodlands", are values for a special kind of value called "figure name". This can in turn be used to define variables, properties and phrases: The turn card image is a figure name that varies. An Old Master is a kind of thing. An Old Master has a figure name called appearance. Figure 1 is the file "Giaconda.jpg". The Mona Lisa is an Old Master. The appearance of the Mona Lisa is Figure 1. To place (F - a figure name) in the gallery: ... (ii) Similarly, names for sound effects, such as "Sound of rustling leaves", are values for the kind of value "sound name". (iii) In the released, blorbed-up Glulx file, figures and sound effects are internally given resource ID numbers which count upwards from 2 in order of their declaration. (Figure and sound numbers can thus be intermingled, if their declarations are.) Resource ID number 1 is reserved for the image of the cover art, if there is any. (See the chapter on Publishing.) To obtain these numbers, if we need them, we can use:

Glulx resource ID of (figure name) ... number
This phrase produces the ID number used in the eventual Glulx file for the given figure.

Glulx resource ID of (sound name) ... number
This phrase produces the ID number used in the eventual Glulx file for the given sound effect.
(iv) Glulx hackers may also like to know that whenever Inform 7 builds a project for Glulx, the Inform 6 code it generates always contains a full copy of John Cater's definitive header file "infglk.h". 22.10. Files Once an Inform project is released, it is playable as a "story file", which is in effect a computer program for a specially IF-adapted design of computer. Story files run in what in computing is sometimes called a "sandbox", a kind of safe play area where it can be guaranteed that they cannot do any harm. This is good, because it means a story file can't be infected with viruses or other malware. If the project's Settings panel has the story file format set to a version of the Z-machine, the story file is so thoroughly boxed in that it cannot even see the bigger computer beyond: it lives in a world of its own. But the Glulx format opens the door a crack, allowing the story file to read and write a small number of data files, which live in a single folder on the bigger computer's hard drive. Why might we want this? Among the reasons are - - to remember what has happened in previous attempts by the player; - to store the player's preferences; - in a two-part story, where each part is an independently released story file, to allow Part I to save some information about its ending which Part II could then pick up and make use of; - to communicate with some external program, such as an Internet service. 22.11. Declaring files Like figures and sounds, files must be declared before they can be used. For instance: The File of Glaciers is called "ice". This creates a new named constant "File of Glaciers" to refer to the file, throughout the source text. We use this name for it whether or not the actual disc file exists yet: it might be one that will only be created if something unusual happens in play, for instance. Quoted filenames should contain only letters and digits, should be 23 characters or fewer, and should begin with a letter. (In particular they can contain no slashes or dots - no subfolders or extensions can be indicated.) The actual filename this translates to will vary from platform to platform, but "ice.glkdata" is typical, stored in some sensible folder. Every file has an owner - not a person, but the project which normally writes to it. Inform assumes that the current project will be owning any file which it declares - the File of Glaciers, for instance. But we can optionally specify that it is owned by somebody else: The file of Boundaries (owned by another project) is called "milnor". The file of Spectral Sequences (owned by project "4122DDA8-A153-46BC-8F57-42220F9D8795") is called "adams". Inform uses ownership to make sure that we do not accidentally read in a file which has nothing to do with us, but merely happens to use the same name. Thus it is an error to read a file whose ownership does not agree with our declaration. Saying that a file is owned by "another project" allows us to read it whatever the owner is (so this can be used for files shared between multiple projects); specifying exactly where it needs to come from allows us to pass information from one project to another. Note that we identify projects using the IFID number - this can be found in the Contents index for a project, or by typing VERSION during play; see the chapter on Publishing for more about IFIDs. Files are indexed in the Contents index, alongside figures and sound effects. Two technicalities. First, constants such as "File of Glaciers" are of a kind of value called "external file" (compare "figure name" and "sound name"). Second, Inform's file-handling is provided for the Glulx machine, which in turn uses the Glk interface. This allows for either text or binary files. Inform's higher-level phrases to do with files, described in this chapter, all use text files, and all declared files are text files by default. But we can optionally add the keyword "binary" to declare a binary file, if needed: The binary File of Glaciation Data is called "icedata". 22.12. Writing and reading tables to external files The main use for files is to store and retrieve data, and the most flexible form of data used by Inform is the Table, so facilities are provided which make it as easy as possible to write and read the contents of a table to files. To save the contents of a table to a file, we use the phrase:

write (external file) from (table name)
This phrase causes the entire contents of the given table to be written out to the given file. Note that files must have been declared, and must be referred to by their Inform names, not by textual filenames. Example: write File of Glaciation Data from the Table of Antarctic Reserves Any blank rows in the table are automatically moved to the bottom, and only the non-blank rows are written.
To load a file back into a table,

read (external file) into (table name)
This phrase causes the entire contents of the given table to be read in from the given file. Note that files must have been declared, and must be referred to by their Inform names, not by textual filenames. Example: read File of Glaciation Data into the Table of Antarctic Reserves Any rows left spare at the foot of the table are automatically blanked. On the other hand if the file is too large to fit into the table - with too many columns or too many rows - a run-time problem is produced.
We can check if a file already exists using:

if (external file) exists:
This condition is true if the file-system used by the player appears to contain a file with the right name. For example, if we declared: The binary File of Glaciation Data is called "icedata". and then tested if the File of Glaciation Data exists, ... then Inform would search for a file called "icedata". (The arrangements for where this might be stored, and its filename extension, vary from platform to platform.)
One unfortunate restriction must be kept in mind. Some of what is stored in tables is solid information whose meaning never changes: the number 342, for instance, means the same to everyone. But other information depends entirely on the current location of certain structures in memory - for instance, a rule is internally referred to by its memory location. This potentially changes each time Go or Replay is clicked, and so it is not safe to pass it from one copy to another, or from one project to another. The only tables which Inform allows us to write into files are those containing "safe" data: numbers, units, times of day and kinds of value with named alternatives. Scenes, rules or rulebooks, in particular, are not allowed. And nor is text - but we can easily get around that, because indexed text (see the previous chapter) is. For instance, the following table can legally be written out to a file, whereas it would have thrown up a run-time problem if we tried it with the surface column defined simply as text: Table of Neptune's Moons moon surface (indexed text) 1 "utterly unknown" 2 "cryovolcanic ridges" 3 "highly irregular and sooty" Example 429 (*): Alien Invasion Part 23 Keeping a preference file that could be loaded by any game in a series. Example 430 (**): Labyrinth of Ghosts Remembering the fates of all previous explorers of the labyrinth. Example 431 (***): Rubies A scoreboard that keeps track of the ten highest-scoring players from one playthrough to the next, adding the player's name if he has done well enough. 22.13. Writing, reading and appending text to files Text can also be saved to a file, and again all file-handling is automatic:

write (text) to (external file)
This phrase makes the given text become the entire contents of the named file. Note that files must have been declared, and must be referred to by their Inform names, not by textual filenames. Example: write "Jackdaws love my big sphinx of quartz." to the file of Abecedary Wisdom;

append (text) to (external file)
This phrase adds the given text to the end of the current contents of the named file (creating it if it does not exist on disc). Note that files must have been declared, and must be referred to by their Inform names, not by textual filenames. Example: append "Jinxed wizards pluck ivy from the big quilt." to the file of Abecedary Wisdom;
The quoted text can, of course, contain substitutions, so can be long and complex if need be. Text from a file is printed back with the text substitution:

say "[text of external file]"
This text expands to the contents of the named file. Note that files must have been declared, and must be referred to by their Inform names, not by textual filenames. Example: "[text of the File of Abecedary Wisdom]"
To copy one file to another, for instance, write "[text of the file of Abecedary Wisdom]" to the file of Secondary Wisdom; Example 432 (*): The Fourth Body Notebooks in which the player can record assorted notes throughout play. Example 433 (**): The Fifth Body An expansion on the notebook, allowing the player somewhat more room in which to type his recorded remark. 22.14. Exchanging files with other programs Provided we declare the files in the right way, it is easy for one project to read a file created by another project. But if we want more rapid communication, between two projects which are each playing at the same time, we need to be more careful. What if project A tries to read the file at the same moment that project B is writing it? To avoid this, we have a concept of files being "ready". A file is ready if it exists, and is completely written, and not in use elsewhere. We have already seen: if the file of Invariants exists... But now we want a stronger condition:

if ready to read (external file):
This condition is true if the file exists and is marked as being ready to read; that is, it is not in a state where another program is currently writing it. Example: if ready to read the file of Invariants, ...
A file cannot be ready to read if it does not exist, so this is a stronger condition. If A and B are attempting communication in real time, both running at once, then Project A should check that an external file owned by B is ready before it tries to read it. Files can also be marked as ready or not ready, in effect claiming them, thus:

mark (external file) as ready to read
This phrase marks that we have finished writing to the given file, so that any external program is welcome to read it now. Example: mark the file of Invariants as ready to read;

mark (external file) as not ready to read
This phrase marks that we are about to start writing to the given file, so that any external program should wait until we're finished if it wants to read the file. Example: mark the file of Invariants as not ready to read;
Possibilities really begin to open up when project A is our story file, but B is not another story file at all: it is some external program such as a Web service, say. (Of course this is harder to set up, since the player needs to have both A and B running at the same time, but for games running on an Internet server this can all be made seamless.) When Inform begins writing a table, or text, to a file, it initially marks the file as not ready: only when the table or text is completely written and the file about to close is the file marked as ready. In order to write non-story-file programs as B, communicating with story files as A, we need to know the file format used by Inform. An Inform file is currently a Unix text file (with 10 as the line division character), encoded as ASCII Latin-1. (We would like to use Unicode at some point in the future, but the Glk and Glulx layers are still not fully converted to Unicode.) It opens with a single header line in the form: * //IFID// leafname The opening character is an asterisk if the file is currently ready, a hyphen if the file is currently not ready. The IFID between the slashes is the IFID number of the project which last wrote to the file. (Marking "ready" or "not ready" does not count as a write for this purpose.) If an external program wrote the file, it should call itself something which will not clash with any story file's IFID. The leafname is the filename text used inside the story file where the file was declared. For instance: * //4122DDA8-A153-46BC-8F57-42220F9D8795// ice Example 434 (***): Flathead News Network Using external files, together with a simple Unix script running in the background, to provide live news headlines inside a story file. Chapter 23: Releasing 23.1. The finished product This chapter and the next are about what to do when we have a complete, finished work on our hands. For almost all of the time when a new work of IF is being written, it lives inside the familiar two-panel spread of the Inform user interface. But that isn't how eventual players will experience it. They will want to play a "story file" in a standard format, and they will do so with a wide range of different interpreters on many different computers or websites, including some -- like mobile phones -- on which Inform itself will not run. So how does a new work of IF reach players? The simple answer, covered in this chapter, is that clicking the Release button instead of Go causes Inform to output a stand-alone story file. But as we will see, Release can do much more than that: it can attach covers, include bibliographic data, make websites and much more. Releasing is the process of making all of the material we want to deliver to our eventual players. But that is only the first step. What do we do with the material when we have it? Printing out a manuscript of a novel is not the same as publishing it. So the next chapter, on Publishing, completes the story. 23.2. Bibliographic data Almost all printed books have a title page and a so-called "imprint" page, often its verso, which make up a description of the contents. The title page gives the name of the book and of the author, while an imprint page contains a variety of details about the edition, the printing, and so on. An ISBN number is allocated so that, from the number alone, any book seller or cataloguer can identify exactly this work. Sometimes other cataloguing information is added, such as the Library of Congress classification. This set of information is called "bibliographic data", and without it libraries and booksellers would be at a total loss. IF has bibliographic data, too. Inform has a number of special named values to hold this - who wrote the work being created, what it is called, what headline it has, what genre it has and what its release number is, and so on. These can be set as follows: The story title is "Mansfield Perk". The story author is "Janet Austen". The story headline is "An Interactive Romance". The story genre is "Romance". The release number is 7. The story description is "In Miss Austen's new interactive novella, Miss Henrietta Pollifax is adopted by the tempestuous landowner Sir Tankerley Mordant, and must make a new life for herself on the rugged moors." The story creation year is 2005. Most of these are self-explanatory. The "story creation year" is provided so that if we need to revise the work to fix some bugs a year later - by no means an uncommon occurrence - then we can make sure it is correctly identified as still being basically a 2005 work. (Just as a book which has had innumerable revised printings may say "First published 1988" on its imprint page.) The "story description" is a piece of text, analogous to the back cover blurb on a book: it might be two or three paragraphs long, so the example above is rather minimal, but it should not be epic in length. As we have already seen, a convenient abbreviation provides that if the first sentence of the source text consists solely of text in quotation marks, then that is considered the title. Thus if the source begins: "Mansfield Perk" then that will be the "story title". Further, we can write "Mansfield Perk" by Janet Austen with the obvious effect: quotation marks around the author's name are optional here, for convenience, but note that we'd better have them in cases like: "Three Men in a Boat" by "Jerome K. Jerome" as otherwise the full stop after the K will end the sentence prematurely. The text of these bibliographic descriptions cannot normally include text substitutions, since they are written into external descriptions of the story file as part of its "binding". One exception is allowed, though: "[']" makes a literal apostrophe, and can be used if we need to override Inform's normal conventions to do with converting apostrophes at the ends of words to double-quotes. For instance: "Summer of [']69" by Buzz Aldrin If the bibliographic named values are not set by the source text, Inform will still need to say something. Unset text and number variables evaluate to "" and 0 respectively, but this would make for a very unhelpful record. So Inform uses the following table instead of any value which is unset: Story title: Untitled Story author: Anonymous Story headline: An Interactive Fiction Story genre: Fiction Release number: 1 23.3. Genres The "story genre" is not used in the banner at all, and exists purely to help librarians. If it is at all possible to do so, authors are asked to use one of the following standard categories: Comedy, Erotica, Fairy Tale, Fantasy, Fiction, Historical, Horror, Mystery, Non-Fiction, Other, Romance, Science Fiction, Surreal These categories are based on those currently used by bookshops, but a few notes may be helpful. "Fiction" is intended for works whose essential purpose is literary, in a way which trumps any subject they happen to have: if Julian Barnes writes a mystery, for instance, a bookshop will shelve it with modern novels rather than in the detective stories section, whereas P. D. James's Adam Dalgliesh mysteries will end up filed with detective fiction even though she has appreciable claims to be an important novelist. "Comedy" is used rather than "humour" to avoid the clash of spellings with "humor". This genre includes parodies. "Non-Fiction" would be used for a work of IF which is essentially a presentation, perhaps in a novel interactive format, of true information. A meticulous simulation of the Great Exhibition of 1851, for instance, might qualify. The distinction between "Surreal" and "Other" is that "Surreal" works contain at least some semblance of narrative, whereas "Other" is intended for works which "abuse" the format to present some entirely different sort of game - Tetris, say, or Minesweeper. 23.4. The Library Card Bibliographic data is useful for two reasons. Firstly, it enables the equivalent of a title page to be printed - traditionally called the "banner" - at the start of play; secondly, Inform uses it to generate the equivalent of a library card for the work, which can be used by other programs to help organise, sort and classify interactive fiction. If the card is given to any other program on any other machine (or an Internet-based archive) then, in principle, that system can know about our work of fiction without a human librarian having to get hold of a copy, play it and laboriously copy out the details. The "library card" is not of course a physical card, but a small "metadata" file which could potentially be transmitted quickly across the Internet. It contains no personal data other than what you choose to put on it, using the sentences documented in this chapter: it does not, for instance, identify your computer or IP address. In any case Inform does not send it anywhere, but merely keeps an up-to-date copy within the project, and includes it when making a release copy of the work. You can always see (a representation of) the current library card for a project at the foot of the Contents index. Authors are asked to play fair, in return, by writing sensible and useful bibliographic information for any work which is likely to circulate to other people; by being honest (writing under a pseudonym is fine, but not impersonating other people); and by conforming to standard practice. The Settings panel of each project contains a tick-box called "Create a Blorb archive for release", and by default this is ticked. "Blorb" is a nonsense word from a popular early 1980s work of IF called "Enchanter", where it was the name of a magic spell whose purpose was to "safely protect a small object as though in a strong box". In the late 1990s, the name was borrowed for a standard format for what might be called the wrapping and packaging of IF. A typical Blorb archive produced by Inform contains the "story file" - the actual program for the game - together with its library card and cover art. Modern IF interpreters such as Zoom for Mac OS X and Unix, and Windows Frotz, can play blorb archives directly, and the authors of Inform hope to make this the normal practice in future. Still, some interpreters cannot read blorbs directly and have to be given the actual story file: so by unchecking the above tick-box, we can insist that Inform creates only that. The disadvantage with this, of course, is that the library card (with all its bibliographic data) and any cover art is lost in the process. 23.5. The Treaty of Babel and the IFID During March and April 2006, an agreement was reached between the IF archive and most of the different systems for creating IF - of which Inform is only one - called the Treaty of Babel. While these different systems create computer programs which are quite different internally, the Treaty provides for works of IF to come with bibliographic data which identifies them in a standard way. Inform is fully compliant with the Treaty. In particular, each new project created by Inform is allocated a unique identification number called its IFID. The IFID is the equivalent for IF of the ISBN of a printed book. Inform copies it onto the "library card" for the benefit of Internet-based libraries which may eventually accession the work. Of course many projects start but never see the light of day, so many possible IFIDs are "wasted": but that hardly matters, as there are plenty more numbers in the world. The important thing is that The IFID number must be unique to this one work out of all the IF ever created Inform will make sure this is true, unless we do something to break this ourselves. For instance, if we take an existing project, copy it as a file, then work divergently on the original and on the copy so that they become two radically different works, they will still each have the same ID. This is a bad thing: if we want to duplicate a project but then turn it into something new, the best way to do that is to create a new project, and to copy and paste the source from the old to the new. 23.6. The Release button and the Materials folder Inform's Release button does two things: it makes a stand-alone, public version of the current project - a "story file" - and it gathers up, or creates, whatever material we want to go with it. The release version of the project can be played by anyone with an "interpreter" - they do not need the Inform application installed on their computers, and they will not be able to see the source text. Released versions differ slightly from the versions playable in the Game panel of Inform, because debugging commands such as ACTIONS are not included with them. (As we've seen, also excluded is any material in the source text under a heading including the words "not for release".) In some cases, if we release along with an interpreter, we can even make the project playable from a web browser, so that the player doesn't need to install any software at all, not even a browser plugin. The Release button also creates a Materials folder for the project, if one doesn't exist already. Inform adopts the following convention: The files associated with the project Whatever.inform should all be kept in a subfolder called "Whatever Materials" in the same folder that contains the project. For example, if we have a project filenamed Magician.inform which lives in a folder called "Works in Progress", then files might be arranged like so: Works in Progress Magician Materials Collegio.pdf Mating Wyverns.mp3 Magician.inform Of course "Magician" might not actually be the title of the project - it might be an abbreviation, or a working title. The name of the Materials folder has to match the name of the .inform file, not the title. Several advanced features of Inform make use of the Materials folder, and the "Release" button is one of them. It creates a further subfolder called "Release" within the Materials folder. This is where it will always place the story file it creates, together with anything released "along with" the story - Inform will not need to put up a dialogue box asking us where to save the story file, because there is already a natural place. For instance, after a successful click on Release, we might then see: Works in Progress Magician Materials Collegio.pdf Mating Wyverns.mp3 Release Collegio.pdf Magician.zblorb Mating Wyverns.mp3 Magician.inform where "Magician.zblorb" is the actual story file produced by Inform. Note that Inform has made copies of the files to be released with it - the idea is that the Release subfolder contains only what Inform makes, and everything in the Release subfolder can be thrown away at any time. This is especially useful if we're releasing along with a website (see below), as then the Release subfolder will be exactly what needs to be uploaded to a server to be shown to the world. Equally, the Release subfolder is what can be zipped up and uploaded to archives or (if small enough) emailed out. 23.7. The Joy of Feelies "Feelie" is a slang word, again going back to the early days of IF, for something tactile included with commercially sold copies of IF games. For instance, Infocom's "Wishbringer" was not just a diskette in a pretty box: the box also contained a map, a letter, an envelope, a magic stone (well, a stone) and a booklet. Most of this was purely for fun, and to flesh out background to the game, but there would usually be clues sneaked into the text or artwork as well. Today's IF is usually not supplied in physical packaging, and not accompanied by physical objects. But authors do sometimes want to include extraneous matter, whether it's a simple read-me file of instructions or a multimedia extravaganza. Inform does not provide facilities to make artwork, movies, soundscapes, booklets, etc.: there are plenty of programs out there to do all of that already. But Inform does help with the collation and packaging-together. For instance, by placing the following sentence in the source text: Release along with a file of "Collegio magazine" called "Collegio.pdf" and a file of "The mating call of the green wyvern" called "Mating Wyverns.mp3". ...we tell Inform that we will also be providing two additional files. Note that in each case we supply a brief description and a filename. The filename should always have a standard file extension for a well-known and thoroughly standardised file format - ".pdf" and ".mp3" are pretty safe: so for instance are ".txt", ".png", ".jpg", ".html". The filename should not include punctuation marks other than the full stop dividing name from extension, and should not exceed 30 characters in length. It is also possible to supply a feelie which is not a single file, but is a mini-website: that is, a collection of interlinked HTML (and perhaps other) files. The convention here would be: Release along with a file of "Baltrazar's Guide to Magic" called "Guide". The absence of a file extension on the filename "Guide" tells Inform that the feelie in question is a mini-website: it is expected to sit inside a folder called "Guide", with its home page being "Guide/index.html". We have seen that Inform takes the story file, which is analogous to the pages of a book, and places it into a Blorb archive, analogous to the binding. These new additional files are not placed in the Blorb, because that would make the Blorb archive rather large (and would hide them from the player, which defeats the purpose). But references to them do appear in the Blorb, so that any interpreter playing the Blorb would be able to tell that there are supposed to be additional files available. Similarly, references are entered onto the library card. 23.8. Cover art Accompanying files are not the only things which can be included in a "release along with" sentence: for instance, we could Release along with cover art, a file of "Collegio magazine" called "Collegio.pdf" and a file of "The mating call of the green wyvern" called "Mating Wyverns.mp3". Cover art can not only be used to advertise a work of IF, it is also displayed to players by certain interpreters, such as Zoom or Spatterlight for OS X, or Windows Frotz for Windows. It is also used on the IFDB (ifdb.tads.org), and by browsing applications. If Zoom is installed, then on Mac OS X Leopard, the Finder shows cover art directly: (Image coverflow.png here) Cover art for a work should be prepared in either JPEG (".jpg") or PNG (".png") format, and we recommend that it should be square, like a music album cover. Programs which notice the cover art for a work of IF are likely to scale this up or down as convenient for their own display purposes, but it would be helpful to provide the original art at 960 by 960 resolution. (Remember, it is intended for use on screen, so providing art at magazine full-page print quality will add nothing and will only make the resulting release an annoyingly large download: even as it is, 960x960 will print out as a pretty respectable CD insert sleeve.) The cover art must not be smaller than 120 pixels in either dimension. To provide cover art, we should create two files: Cover.jpg (or .png), and a reduction of the image to a smaller "thumbnail" version called Small Cover.jpg (or .png). These should be placed in the project's Materials folder. For instance, we might have: Works in Progress Magician Materials Collegio.pdf Cover.jpg Mating Wyverns.mp3 Small Cover.jpg Magician.inform (supposing that, as in the previous examples, "Collegio.pdf" and "Mating Wyverns.mp3" are the filenames of two feelies that accompany the release). "Small Cover.jpg" should be a reduction of the main cover art image "Cover.jpg" to exactly 120 by 120 pixels. 23.9. An introductory booklet When IF is aimed particularly at people who have never played IF before, there are certain conventions which it's a good idea to explain, or players will simply not know what to do. It can become a chore writing a clear set of instructions, and then there is the further nuisance of explaining about the need for an interpreter program to play the IF story file. To alleviate this, Inform can "Release along with an introductory booklet", as for instance in this example: Release along with cover art, the introductory booklet, a file of "Collegio magazine" called "Collegio.pdf" and a file of "The mating call of the green wyvern" called "Mating Wyverns.mp3". The introductory booklet is a standard 8-page PDF file, written and designed by Emily Short, which contains all the basic information needed for a player to get started. It has been written to be as general-purpose as possible, in the hope of being useful for a range of widely different works of IF. There will certainly be works to which it would not be an appropriate supplement, and some authors will certainly prefer to write their own notes for players, but of course it is not compulsory. By making it available as a convenience, the authors of Inform do not intend to say that these are the "official" instructions or that others are not. It is simply intended as a time-saver. 23.10. A website Much of the published IF of the last twenty years came with a brief text file describing what it was - a release note. Today it makes more sense to write this as a small web page, which can either be placed online, or simply distributed as part of the release. Inform is able to manufacture such a website automatically. We request this by writing, for instance, Release along with cover art, a website, a file of "Collegio magazine" called "Collegio.pdf" and a file of "The mating call of the green wyvern" called "Mating Wyverns.mp3". where the list of ingredients now includes "a website". In fact, Inform makes only a single web page, called "index.html", which it places in the materials folder (as set up in the previous section): this then contains suitable links to all the other material, such as the cover art images, if they are also provided. For instance: (Image sampleweb.jpg here) After a successful release now, then, we should see: Works in Progress Magician Materials Collegio.pdf Cover.jpg Mating Wyverns.mp3 Release Collegio.pdf Cover.jpg index.html Magician.zblorb Mating Wyverns.mp3 Small Cover.jpg Small Cover.jpg Magician.inform 23.11. A playable web page Modern web browsers are now so powerful as computing environments that they almost amount to general-purpose computers in their own right. The websites made in the previous section were passive, and simply displayed information about a story file. But it's also possible to make a more active page - one which can play the story file, right inside the browser, for anybody who visits. To make such a page, we must: Release along with an interpreter. This automatically releases along with a website as well, since we need the website in order to house the new page, which will be called "play.html". This page will be bundled up with a customised copy of a story file interpreter coded in Javascript - in effect, a program for a web browser to follow - and a suitably encoded version of the story file. The practical effect should be that anyone visiting the page with any modern browser can just play. Inform ships with the "Parchment" and "Quixe" interpreters built in, one intended for each of the story file formats it can output - so by default Inform uses Parchment if the format (on the project's Settings panel) is set to Z-code, and Quixe if the format is Glulx. But Inform also supports the use of any other interpreter the author wants to try (including, for instance, later versions of Parchment or Quixe than the built-in ones). If we have access to an exotic Javascript-based interpreter called, let's say, "Urbzig", then we can install it by putting it into the "Templates" subfolder of the "Materials" folder for the project, and then ask for it to be used instead of "Parchment" like so: Release along with the "Urbzig" interpreter. 23.12. Website templates Web pages are very idiosyncratic things and Inform will almost certainly not produce exactly what we want. What it actually does is to take an existing "template" web page, and paste in the relevant information to make the final product. So by starting with a different template, we can end up with an entirely different-looking web page: like this one, for instance - (Image sampleweb2.jpg here) The template ordinarily used by Inform is called "Standard" and comes built in. (A second built-in template, "Classic", imitates the look used in 2005-08. The word "classic" here is to be understood in the sense of Classic Mac OS, the classic Doctor Who adventure "Time and the Rani", classic Mayan civilisation, and so forth - really pretty awful.) Any other templates we must make ourselves, giving each one a different name, by convention a single word. In this section, we'll make a new one called "Platinum". Suppose we write: Release along with cover art, a "Platinum" website, a file of "Collegio magazine" called "Collegio.pdf" and a file of "The mating call of the green wyvern" called "Mating Wyverns.mp3". This is identical to the previous version except for the "Platinum": note the quotation marks. When it needs to find a template, Inform searches the following places in sequence: (a) the "Templates" subfolder of the project's own Materials folder, if this subfolder should exist; (b) the "Templates" folder in the user's own library - on Mac OS X, this is: ~/Library/Inform/Templates and on Windows: My Documents\Inform\Templates (c) the built-in stock of templates, currently only "Standard" and "Classic". What Inform looks for is a folder name matching that of the template - so in our case we need to provide a folder called "Platinum", and put it in either location (a) or (b). The template folder is expected to contain some combination of the following files: Platinum index.html source.html style.css (extras).txt If any of these is missing, Inform uses the one in "Standard" instead. In practice, this means the easiest way to create a new template is to supply just a new CSS file, which can change the colour, font, type size, and position of more or less everything in the site. There are two HTML pages here, one for the main front page, the other for pages of displayed source text (if we release along with the source text - see later in the chapter). The CSS file defines styles of text - sizes, fonts, colours, and so on - and positions material on the page. The "(extras).txt" - which is optional, of course - allows additional HTML pages, images, movies and so on to be added. If any of the four files is not supplied, the "Standard" version will be used instead. The "Standard" HTML files have been put together so that almost anything needed can be achieved with a CSS file alone - so in practice, the easiest thing is to supply just: Platinum style.css We probably want to start from the "Standard" version of "style.css" and edit in a few changes; the easiest way to get a clean copy of "Standard"'s CSS file to work on is to release the project with a "Standard" template, which causes this default "style.css" to appear in the "Release" subfolder of the project's Materials folder. (But it's wise to move the file out of "Release" before starting to edit it - files in "Release" are overwritten by Inform whenever a release is made.) This is not the place to describe how CSS works. CSS is a more or less universal format today for describing how web pages should look - their style rather than their content. A dazzling variety of possibilities can be seen at the excellent: www.csszengarden.com but of course there are many, many other textbooks and websites which describe CSS. 23.13. Advanced website templates The following describes how Inform uses the extras file and the two HTML pages in a template, and will only be needed if a new template has to make changes so radical that altering the CSS alone won't be enough. The optional "(extras).txt" file - note brackets - is a text file which contains a list of named extras to throw in. For instance: easter.html egg.png These named files need to be present in the template folder. Files with the extension ".html" go through the placeholder expansion process just like the index and source pages; all other files are copied verbatim. HTML templates like "index.html" and "source.html" are fully valid HTML pages in their own right, though they have placeholder text where Inform will substitute the project's bibliographic data (see below). The "" element should include a reference to "style.css", which of course will mean the CSS file given in the template (or the one from "Standard" if no CSS file is given) - for instance, When it turns the template into the final web page, what Inform does is to replace certain capitalised words in square brackets with the appropriate text: [TITLE] becomes the story title [AUTHOR] becomes the author's name [YEAR] becomes the story creation year [BLURB] becomes the story description [RELEASE] becomes the release number [COVER] becomes an image of the cover art (the small 120x120 cover image) [DOWNLOAD] becomes the download link [AUXILIARY] becomes the list of feelie-like files, if any [IFID] becomes the IFID [STORYFILE] becomes the "leafname" of the story file, e.g., "Bronze.gblorb" [TEMPLATE] becomes the name of the template used to make the page [SMALLCOVER] becomes the filename of the small cover image [BIGCOVER] becomes the filename of the large cover image [TIMESTAMP] and [DATESTAMP] become the time and date of releasing Everything else is left alone. In source pages, five further placeholders are available: [SOURCE] becomes the portion of the source text on this page [SOURCELINKS] becomes the navigational links [SOURCENOTES] becomes the footnote matter at the bottom of the source [PAGENUMBER] and [PAGEEXTENT] are such that the text "page [PAGENUMBER] of [PAGEEXTENT]" produces, e.g., "page 2 of 7" Both [SOURCE] and [SOURCENOTES] must exist on the page, and [SOURCENOTES] must appear after [SOURCE] does in the file. (Of course the CSS in "style.css" might move the copy around on screen, but that's another matter.) 23.14. Republishing existing works of IF Some long-time users of Inform will have projects which were originally made using the very different Inform 6 language. Story files produced with Inform 6 do not have any of the extra touches in this chapter: in particular, they have no cover art and no bibliographic data, which makes them rather plain and anonymous to newer Treaty of Babel-equipped programs like Zoom, Spatterlight or Windows Frotz. To help with this, today's Inform can republish an Inform 6 project by combining an Inform 7 source text which contains only release instructions and bibliographic data with an already-compiled Inform 6 story file. We do this by writing a short source text which contains: Release along with an existing story file. We then place the story file in the Materials folder, with the filename "Story.z5" or "Story.z8" - depending on whether the story file is a version 5 or version 8 Z-machine story file (at present, version 6 story files are not supported, but there are very few of these). This must also match the corresponding choice of format in the Settings panel. And we can now use the Release button to obtain the goods. An existing story file can take advantage of all of the extra features - cover art, titling, website, feelies and so forth - earlier in this chapter, but not those - walkthrough, source text, map - which are still to come. The following is a typical example of a source text used solely to bind up an old Inform 6-compiled story file: "Curses" by Graham Nelson The story genre is "Fantasy". The story headline is "An Interactive Diversion". The story creation year is 1993. The release number is 16. The story description is "It's become a matter of pride now not to give up. That tourist map of Paris must be up here somewhere in all this clutter, even if it has been five years since your last trip. And it's your own fault. It looks as if your great-grandfather was the last person to tidy up these lofts..." Release along with cover art and an existing story file. 23.15. Walkthrough solutions Since the earliest days of IF, players have distributed solutions to well-known games, to help out other players at their wits' ends. The commonest format for these is a list of commands to type, sometimes with notes in the margin, and such a solution is called a "walkthrough", since it walks a player through the game. Few authors publish solutions of their own works, but many supply their testers with solutions, especially towards the end of testing, or submit a solution as part of a competition entry. To help with this, Inform can generate such a walkthrough solution automatically: Release along with a solution. Inform will then place a file called "solution.txt" inside the "Release" folder. The solution might look like so (although probably much longer): Solution to "Memoirs of India" by Graham Nelson Choice: INVENTORY -> go to branch (1) EAST -> go to branch (2) Branch (1) DROP MANUSCRIPT SOUTH Branch (2) INVENTORY ... Always a good idea GIVE MANUSCRIPT TO THOMAS Inform does not, of course, know how to solve IF all by itself, but derives the solution from the project's Skein. Since the Skein will have been used in testing the game, it will very likely contain a perfect solution - or several different ones, taking the game to a variety of possible endings. In the example above, there are two possible winning lines, which diverge right from the first move. (There can be further divergences: for instance, if branch (2) splits, it will split into branches called (2.1), (2.2), (2.3) and so on.) But the Skein will also contain plenty of unwanted diversions, so Inform does not rewrite the entire Skein as a solution. Instead, it looks for knots in the Skein which have been annotated. Any knot whose annotation begins "***" (three asterisks) is considered to be a final, winning move. (It is probably a good idea to lock such a knot once it has been annotated thus, too.) We can mark any number of knots "***" since, after all, we can declare any number of lines of play as possible solutions. Inform then constructs the solution out of all lines of play in the Skein which lead to "***" endings, and ignores other threads. (Image annots.png here) Annotations other than "***" in the Skein are turned automatically into comments in the solution text. For instance, the knot for the INVENTORY command in the second branch above was annotated "Always a good idea", and this was transcribed into the solution. (If an ending knot is annotated with, say, "*** Happy ending!" then the "***" marks it as an ending, and "Happy ending!" is added as an annotation to that ending.) By default, the solution text is not linked from our webpage, on the assumption that we may want to generate a walkthrough but not immediately advertise it to players. If we wish to change this, we may write instead Release along with a public solution. The terms public and private may also be applied to other elements we are having Inform generate to include on our webpage: see also the notes on private source text, below. 23.16. Releasing the source text Most authors will not want to publish the source text alongside the work itself, because this gives away all of its secrets. Inform provides the option mainly for the sake of the examples published on its own website, where making the source available is the whole point. But anyone is welcome to use the option, of course: Release along with the source text. If Inform is not also generating a website, this produces a plain text file called "source.txt" in the "Release" folder, and there is nothing more to be said. However, if a website is also being released, the source is also converted to a suite of web pages which are linked to and from the home page. (Each heading with substantive content is placed on its own web page, with the opening page containing a contents list.) Comments in the source are rendered in grey. As a special feature, any comment which begins with an asterisk is considered a footnote and is printed below the source text, with a link. Thus comments thus: Hercules is a demigod.[* We're using Greek spellings so he ought to be Heracles, but players are so much more familiar with Hercules.] will be printed more like so: Hercules is a demigod.[1] ... Note [1]. We're using Greek spellings so he ought to be Heracles, but players are so much more familiar with Hercules. Footnotes are automatically numbered from 1 on each source page. By default, the source text is linked from our generated webpage, if we are releasing with a webpage. If we wish to change this, we may write instead Release along with the private source text. This will create a text file containing the source for our story, and place this file in our release folder, but not create a link so that the player can find it. Finally, we can: Release along with the library card. which releases a stand-alone XML file in 'iFiction' format for the bibliographic data on the story file; this is the same data embedded in the blorb file itself, but having an external copy makes it easier to see what Inform has done, and some external programs can read iFiction data like this. 23.17. Improving the index map As we have seen, "Release along with..." allows us to package up a work of IF with all manner of extra materials. But what are these to be? One popular option is to produce a map - sometimes partial, sometimes obfuscated - and supply that with the game: besides, there are some IF competitions where the rules require that the referee is supplied with a map even if the players are not, and failing that, it is sometimes nice to be able to print out a map of a work in progress. The World map in the Index tab is heavily stylised and cartoonish, intended to be clicked on or moused over, and viewed in a browser: although it is, in fact, possible to print it, the results are not very good. Fortunately, the same underlying map mechanism can be used to output something more useful and very much more customisable, as we shall see. The map-maker is one of the most complex parts of Inform, even though it actually contributes nothing to the final story file: the problem of how to draw up a "correct" map from the source text is by no means easy to solve. Inform tries, but it often gets things wrong. Its general practice is to place rooms on a square grid (actually a cubic lattice, as it works in three dimensions), but not all conceptual maps fit well onto this, and Inform often annoyingly puts a particular room in the "wrong" place. For instance, suppose Inform puts "Didcot" east of "Abingdon" and this makes the geometry look different to what we had in mind. We can correct with: Index map with Didcot mapped southeast of Abingdon. Note that this says nothing about exits from any room to any other room, and changes the final work of IF not at all: it simply helps Inform to draw the map index. (Instructions like this one are treated as being almost certainly true, but Inform does not quite always obey: it will never allow two rooms to be superimposed at the same grid position, no matter what we have asked in "Index map with..." instructions.) The same trick is useful if we have a situation like so: Inside of Sweeping Sands is Beach Hut Interior. "Beach Hut Interior" is a single room which does not connect to the rest of the map by any of the ten spatial directions, so Inform does not place it on the main map but instead moves it off out of the way in a map of its own. Given that it's just a single room, however, we might prefer to put into a convenient otherwise empty grid position like so: Index map with Beach Hut Interior mapped west of Sweeping Sands. Finally, note that this trick also ensures that the two locations are mapped on the same level vertically, and can be useful in cases where room A is both north of and above room B: Inform will want A to be higher up than B, but we can insist otherwise. 23.18. Producing an EPS format map The "Index map with..." instruction is a much more varied thing than hinted at in the previous section, and its general form is Index map with [instruction] and [instruction] and ... and [instruction]. where the instructions can be of four different forms, as follows: [room A] mapped [direction] of [room B] EPS file rubric [text] ... and some optional details ... [setting] of [whatever] set to [value] We have already seen the first of these instructions. The second is short and has a fixed wording: EPS file so can be invoked by typing "Index map with EPS file.", for instance. EPS stands for Encapsulated PostScript, which is a standard file format for line art. EPS files can be edited with sophisticated graphics programs such as Adobe Illustrator, and can be used as illustrations in many word-processors and page layout programs. They can also be converted to PDF by Mac OS X Preview, or used in Linux or Windows with the open-source Evince viewer. We need a line-art format because the map produced will never be exactly what we want: we are probably going to end up hacking it to change the fonts, add some drawings, tidy up the spacing and so on. A really large map will end up using quite a large "canvas", in EPS terms; it may be necessary to shrink it down in order to get it onto an A4 page, or to adjust whatever editing software is used to "custom paper size". When the map-maker has been given the "EPS file" instruction, it writes an attempt to draw the current project's map in EPS format as a file onto the desktop, with the filename "Inform Map.eps". Note that Inform will over-write any existing file of this name: but that is intentional, because one usually ends up tweaking and rebuilding the project over and over to get the map just so, and it would be tiresome for Inform to produce endless copies "Inform Map 19.eps", etc. (The reason the EPS file is not placed in a project's Materials folder is that it is not going to releasable to the public as it stands: for one thing it will be too raw, and for another, EPS is not a format everyone can read. It is provided as raw materials.) 23.19. Settings in the map-maker The map-maker has altogether 35 named settings, and tweaking these can affect the result in ways which vary from the subtle to the grotesque. An important point is that the map-maker deals separately with the three levels in its working: the big picture of the whole map; each of the vertical slices which contain sub-maps; and finally all of the individual rooms. For instance, we might have 67 rooms, arranged on 3 vertical levels, all shown on one big map: Inform will try to show these stacked above each other, with the highest level at the top of the map, then the middle level, then the bottom level. Moreover, not only does the whole map have its 35 settings, but each level has its own independent collection of those 35 settings, and so does each individual room. So the actual number of variables in our example is 1+3+67 = 71 times 35, which is a lot. The convention is that setting the value of S (some setting, let's say) for something affects not only that thing, but also everything inside it, unless they have their own individual settings for S. For example: one of the settings is called "room-size", and is the size of the little square boxes representing a room, measured in points. (One point is 1/72 of an inch, so 72 points equals 1 inch: it's a traditional printer's measure.) Suppose we write: Index map with room-size set to 36 and room-size of level 2 set to 28 and room-size of the Hall of Kings set to 52. The first instruction sets the value of "room-size" for the whole map (note the lack of an "of..."); the second for level 2 of the map, and the last for a single room only. The result is that the Hall of Kings is drawn as 52x52 point box, all rooms on level 2 are 28x28 (except the Hall of Kings, if it's on level 2), and all others are 36x36, half an inch square. The setting instruction also allows three other useful forms. A setting "of the first room" applies to the room in which the game begins: we might for instance write Index map with room-outline-thickness of the first room set to 2. which gives this special room a bolder edge to it, since the default value is 1. We can also apply settings not just to single rooms but to all rooms of a given kind: A rivery room is a kind of room. Index map with room-colour of rivery rooms set to "Navy" and room-name-colour of rivery rooms set to "White". Lastly, we can apply settings to all rooms in a given region: Northern Oxfordshire is a region. Hampton Poyle and Steeple Barton are in Northern Oxfordshire. Index map with room-name-font of Northern Oxfordshire set to "Helvetica-Oblique". (Note that rooms and regions don't have their own individual sets of the 35 settings: what happens is just that instructions like the last one change more than one room at once.) 23.20. Table of map-maker settings Note that all map-maker settings have single word names, though many are hyphenated, and that "colour" is always given the English and Canadian spelling, not the American form "color". font font (named in double-quotes) minimum-map-width integer (measured in points: 72 = 1 inch) title text (in double-quotes) title-size integer (measured in points) title-font font (named in double-quotes) title-colour colour (named in double-quotes) map-outline on/off border-size integer (measured in points) vertical-spacing integer (measured in points) monochrome on/off annotation-size integer (measured in points) annotation-length integer (length to abbreviate down to) annotation-font font (named in double-quotes) subtitle text (in double-quotes) subtitle-size integer (measured in points) subtitle-font font (named in double-quotes) subtitle-colour colour (named in double-quotes) grid-size integer (measured in points) route-stiffness integer (Bezier spline curve scale factor) route-thickness integer (measured in points) route-colour colour (named in double-quotes) room-offset offset (in percentages of grid-size) room-size integer (measured in points) room-colour colour (named in double-quotes) room-name text (in double-quotes) room-name-size integer (measured in points) room-name-font font (named in double-quotes) room-name-colour colour (named in double-quotes) room-name-length integer (length to abbreviate down to) room-name-offset offset (in percentages of grid-size) room-outline on/off room-outline-colour colour (named in double-quotes) room-outline-thickness integer (measured in points) room-shape shape (named in double-quotes) 23.21. Kinds of value accepted by the map-maker Integer values are typed in the usual way: 3, -72, etc. Text is in double-quotes: "Map of Lower Delta", etc. Font names are in double-quotes: "Helvetica", etc. Note that Inform makes no effort to look for such fonts: if we give the name of a font we haven't got, the result will probably be that the map's EPS file will be displayed in various applications with Courier (which looks like bad typewriting) substituted. All fonts are by default equal to the global "font" setting (by default equal to "Helvetica"), so changing "font" for the whole map affects everything not explicitly specified as having a different font. Shape names are in double-quotes with lower case. At present, the only legal shapes are "circle", "square" and "rectangle". On/off values are written just thus: on, off. No quotation marks. Offset values are actually pairs, and are written as two numbers (possibly negative numbers) joined by an ampersand, as in the example: "Index map with room-offset of Botley set to 10&-30." Note lack of spaces around the ampersand. This means that Botley's room is displaced from its correct grid position on the EPS map by 10% of the grid size eastwards, and 30% southwards. (The grid size is the distance between one grid position and the next: displacing Botley by -200&0 would move it two whole grid positions westwards.) The route-stiffness setting is used when drawing routes between two rooms. These are drawn as Bezier curves, a standard way to make a smooth curve not only travel from A to B but also from pointing in a given direction at A to ending up pointing in a given direction at B. Thus a Bezier curve may turn a route round so that it leaves A pointing west, but curves around to enter B from the south. (Most routes involve leaving in one direction and arriving in the opposite direction, of course, and in those cases a Bezier curve is just a straight line.) The stiffness factor for a given room measures how much the curves are allowed to warp around in order to force them to arrive at that room from exactly the right compass bearing. The default is 100. Raising to, say, 250 can force curved paths into freakish zig-zags: whereas lowering to 1, the minimum, may make the route arrive at completely the wrong bearing. (Formally speaking: at each end of the route, a "control point" for the Bezier curve is made by taking the centre point of the room, then adding the relevant compass bearing's vector, scaled up by the route-stiffness as a percentage of the grid size.) Colour values are named and in double-quotes. These names are the same as those for the traditional set of web-page-safe colour chips, as follows: "Alice Blue" "Antique White" "Aqua" "Aquamarine" "Azure" "Beige" "Bisque" "Black" "Blanched Almond" "Blue" "Blue Violet" "Brown" "Burly Wood" "Cadet Blue" "Chartreuse" "Chocolate" "Coral" "Cornflower Blue" "Cornsilk" "Crimson" "Cyan" "Dark Blue" "Dark Cyan" "Dark Golden Rod" "Dark Gray" "Dark Green" "Dark Khaki" "Dark Magenta" "Dark Olive Green" "Dark Orange" "Dark Orchid" "Dark Red" "Dark Salmon" "Dark Sea Green" "Dark Slate Blue" "Dark Slate Gray" "Dark Turquoise" "Dark Violet" "Deep Pink" "Deep Sky Blue" "Dim Gray" "Dodger Blue" "Feldspar" "Fire Brick" "Floral White" "Forest Green" "Fuchsia" "Gainsboro" "Ghost White" "Gold" "Golden Rod" "Gray" "Green" "Green Yellow" "Honey Dew" "Hot Pink" "Indian Red" "Indigo" "Ivory" "Khaki" "Lavender" "Lavender Blush" "Lawn Green" "Lemon Chiffon" "Light Blue" "Light Coral" "Light Cyan" "Light Golden Rod Yellow" "Light Grey" "Light Green" "Light Pink" "Light Salmon" "Light Sea Green" "Light Sky Blue" "Light Slate Blue" "Light Slate Gray" "Light Steel Blue" "Light Yellow" "Lime" "Lime Green" "Linen" "Magenta" "Maroon" "Medium Aquamarine" "Medium Blue" "Medium Orchid" "Medium Purple" "Medium Sea Green" "Medium Slate Blue" "Medium Spring Green" "Medium Turquoise" "Medium Violet Red" "Midnight Blue" "Mint Cream" "Misty Rose" "Moccasin" "Navajo White" "Navy" "Old Lace" "Olive" "Olive Drab" "Orange" "Orange Red" "Orchid" "Pale Golden Rod" "Pale Green" "Pale Turquoise" "Pale Violet Red" "Papaya Whip" "Peach Puff" "Peru" "Pink" "Plum" "Powder Blue" "Purple" "Red" "Rosy Brown" "Royal Blue" "Saddle Brown" "Salmon" "Sandy Brown" "Sea Green" "Sea Shell" "Sienna" "Silver" "Sky Blue" "Slate Blue" "Slate Gray" "Snow" "Spring Green" "Steel Blue" "Tan" "Teal" "Thistle" "Tomato" "Turquoise" "Violet" "Violet Red" "Wheat" "White" "White Smoke" "Yellow" "Yellow Green" 23.22. Titling and abbreviation The main title of the map is the value of "title" for the whole map, so for instance we might write: Index map with title set to "Oxford and its Environs". The subtitle settings apply to the subtitles used for each of the levels, so for instance Index map with subtitle of level -1 set to "Tunnels and Sewers". Names of individual rooms can be controlled with: Index map with name of Radcliffe Camera set to "Library". (By default, the name of a room is its name in the main IF project, of course.) The smallest writing on the map is normally that used to label unorthodox or unclear exits (in particular, those going from one layer to another): this is what the "annotation" size, font and colour are used for. For most ways to set up the map, it's a practical necessity to abbreviate names of rooms, or they will spill out all over each other. Inform does this using the "room-name-length" setting. (The "annotation-name-length" is analogous.) For instance, if this setting is 5, then Inform will reduce the text of a name to at most 5 characters. It does this by successively throwing out spaces, lower case vowels, then other lower case letters, punctuation marks and finally upper case letters, always starting at the back of the name and working inwards: the process stops as soon as the name is short enough. For instance, "Reading" is abbreviated to "Redng", "Shangri-La" to "Shn-La" and "Cloud-Cuckoo-Land" to "C-C-L". The result can be a little comical, but is surprisingly unambiguous in practice. Abbreviation can effectively be abolished by raising the "room-name-length" to 128 (the highest permitted level), and note that the setting can be changed for individual rooms, so it is possible to have some room names abbreviated and others not, or in different degrees. Example 435 (*): Baedeker Creating a floorplan of the cathedral using the locations from previous examples. Example 436 (*): Port Royal 5 Port Royal scenario given instructions for an EPS map. Example 437 (*): Bay Leaves and Honey Wine Creating a map of Greece using the locations from previous examples. 23.23. Rubrics Lastly, we can add our own arbitrary text to the map: perhaps to annotate points, perhaps just to add more heading matter (such as the author's name, or the date). Each individual line added - and only single lines can be added, not typeset paragraphs - is called a "rubric". (There can be up to 100 of these.) We can create a rubric like so: Index map with rubric "Here Be Wyverns" size 16 font "Helvetica-Oblique" colour "Thistle" at 150&0 from Cloud-Cuckoo-Land. This gives rather more detailed information than is needed: "size 16" could have been omitted, giving us 12-point type by default, and similarly there is no need to specify a font unless it differs from the main "font" setting for the whole map; and the colour will be black if unspecified. The "at" position does need to be given, though. Note that it is relative to a given room on the map, and that the position specified is that of the centre-point of the text. (If we had written just "at 100&100", say, that would specify a position relative to the bottom left hand corner of the map.) So, for instance: Index map with rubric "trapped door" size 8 at -60&-60 from Longwall. would add a little 8-point-type safety tip for naive map-followers. Inevitably, the settings in the map-maker will fail to get exactly the effect desired (though they will offer an excellent opportunity to waste entire days). But that is the whole point of producing output in EPS format: Inform aims not to produce final print-ready professional art, but to produce the raw material for making that final work of art. And if all that's required is a sketch-map, then Inform's output should be good enough quickly and without too much fuss. Chapter 24: Publishing 24.1. Finding a readership So the new work of IF is written, and tested, and has all its bibliographic data and a fancy cover illustration lined up. What next? There is a thriving community of readers and writers of interactive fiction, and it is sometimes supported by grants from arts foundations and other cultural bodies: there's increasing attention from the academic world, and a general consensus has gradually grown that interactive fiction is a "valid" artistic medium for expression. Like poetry, it is something that a few people like a lot, and which most people can see the point of, even if they don't read it themselves. Over the last thirty years, a few authors have established durable reputations: they give occasional newspaper interviews, and have a very low-key kind of fame. There are competitions, and annual awards ceremonies. Newcomers are always welcome. (Image quilt.jpg here) With some important exceptions, most works of interactive fiction have never been "published" in the sense of being issued for sale by a for-profit company. For the most part, IF has not been commercially valuable since about 1987. Successful authors of IF generally take the view that while they could, perhaps, make a very modest amount of money from sales, it would be a nuisance to collect and make no meaningful difference to their incomes; it would cut the number of readers, whereas one wants the satisfaction of being read; and besides, the whole culture of IF has always been characterised by giving and sharing. (Inform itself is free.) Inform has nevertheless been used to produce commercial works (generally add-ons or bonuses to other games), and users are very welcome to sell works created by Inform with no royalty or requirement for rights clearance. It's also widely used in education, and as a prototyping tool for other kinds of game. 24.2. How a novel is published Suppose that a (traditional) novel has been delivered to a publisher: the author has handed it over as a pile of twenty chapters of prose, and feels that it is finished. In fact there is much still to do: (a) Editing. An editor works through the book, looking for problems in the plot, uneven passages, difficulties of tone and a hundred other nuanced points. The author generally then revises the book and submits again. (b) Copy-editing. A copy-editor fixes punctuation errors, awkwardly worded sentences and other low-level problems. (c) Bibliographic data is added. (d) Printing. The text is given a clean, readable rendition, and no longer looks like a home-made typescript. (e) Cover art is added. Even unillustrated novels have pictorial covers, and these images are often used to set the tone for the book - they set the reader's frame of mind, so something more is happening than mere marketing. (f) A back cover blurb is added. This will also find its way into catalogues, onto book trade databases, appear on Amazon.com and so forth. Both a description and a lure, it gives a flavour of the work without actually being any part of it. (g) Binding. Not only are the inside pages printed, but maps, plates of illustrations, free CDs, fold-out charts, etc., may be tipped in to the binding. (h) Legal deposit. Copies are lodged with libraries of record, such as the British Library or the Library of Congress, to ensure that the work cannot be lost from cultural history. (In most countries, this is a legal obligation for publishers.) (i) Shipping. Copies are sent out to bookshops. (j) Publicity. The author and publisher combine to put out the word, circulate leaflets, put up posters and so forth. (k) Reviews and awards. Reviews are published, usually stirring up interest in the book. These having been stellar, a few months later the author bashfully accepts a Pulitzer Prize, the Booker or some similar token of cultural esteem. 24.3. How interactive fiction is published If we take the eleven novel-publishing stages of the previous section in order, we find that pretty well the same business goes on for works of IF. (a) Editing. Working with a small number of trusted play-testers, and taking their responses seriously even when inconvenient, will almost always produce an immeasurably better work: not just better functionally, but better artistically, and more enjoyable. Play-testers can usually be recruited by placing an ad on www.intfiction.org/forum. (b) Copy-editing. Play-testers will also pick up small stuff - spelling mistakes, and punctuation errors - but note that Inform for OS X will spell-check our source text on request. (c) Bibliographic data is added. (d) Printing. Clicking Inform's Release button is the equivalent the-die-is-cast moment. (e) Cover art is added. As we saw in the previous chapter, Inform can add a cover image as part of the Release process, though it will not itself draw and design that image - like a printer, it expects to be supplied with the original. (f) A back cover blurb is added. Inform does indeed allow us to compose such a piece of text and include it with the work's bibliographic data. (g) Binding. The story file, which is akin to the inside pages of a book, is combined with its cover art, bibliographic data, and also with other non-textual materials provided by the author (booklets, sound samples, images, etc.). Inform does much of this automatically, producing a composite object called a "blorb". (h) Legal deposit. The work is uploaded to the IF Archive (www.if-archive.org), whose librarians shelve it in the appropriate section. More on this later. (i) Shipping. A work of IF is electronic rather than physical, so nothing is actually moved, but many authors like to put their works on their own websites as well as placing them in the Archive. (j) Publicity. Authors often announce a new work on IFDB (ifdb.tads.org). Authors often also set up a personal web page about the work. Inform can generate such a web page automatically, as we saw in the chapter about releasing new works. (k) Reviews and awards. The IF community has competitions and awards in abundance, and several websites gather reviews. It is usually safe to say that a well-written work will not go unnoticed if it is sensibly publicised. 24.4. The IF Archive Publishing an IF game consists of two steps. One is the technical task of making the game available to players - unless the plan is simply to email it to close friends, that means hosting it somewhere on the Internet. The second is the promotional task of letting people know the work exists, and where to find it. It is a community tradition that all serious work is uploaded to the IF Archive, which is IF's answer to a national library. This is a mirrored, stable collection of thousands of interactive fiction games and programming languages, manuals, fanzines, maps, walkthroughs, and other materials. As such, it's likely to stay around even if a personal website goes off-line; it's also the primary resource for people doing scholarship on interactive fiction (and there are a growing number of these). The Archive is very much a library, for long-term archiving, rather than a book-store. The catalogue is sober and textual, and there are no visual shop-windows, or posters advertising new titles hot off the press. Newcomers sometimes need practice finding their way around. And the Archive hosts story files (and associated manuals, as appropriate) but not advertising for them - it does not provide web-hosting for authors to set up mini-sites. Uploading a work to the IF Archive is not too difficult, and can be done in two ways. One way is to use the archive's web form at: http://www.ifarchive.org/cgi-bin/upload.py The other is to create a new page at the Interactive Fiction Database, at: http://ifdb.tads.org/ It's then possible to upload the story file to the IF Archive from IFDB. This is easiest all round, since it allows both IFDB and IF Archive to be updated at once. In either approach, an author chooses and uploads a file, and accompanies it with a name and email address (so that the archive maintainers can verify the legitimacy of the work). The "About this file" field is for a line or two explaining what the game is -- its full title and any critical information -- and is used in generating the archive index. This is normally much shorter than the "blurb" described earlier. There's also a field to suggest where in the archive the game should be stored, but this is optional and intended chiefly for people expert in how the archive is filed. The archive maintainers will file a new story file in the obvious directory for its format. For Inform works, that means other Z-Machine - "z-code" - or Glulx story files. The maintainers sometimes place the same story file in multiple places in the Archive, using links. As with all large libraries, it takes the Archive a little while for new acquisitions to be processed. When this happens, one of the volunteer maintainers will email with the official URL from which anyone can now download the story file. Committing a game to the Archive is meant to be permanent. While the maintainers will happily replace older versions of games with new improved releases, they are less eager to remove games entirely. If that doesn't seem appealing, or if we do not want our game to be treated as freeware with essentially unlimited distribution, the Archive may not be a good choice. But it is deeply valued by the IF community, and has saved many works which could otherwise easily have been lost forever. Many contributions important in the history of IF were made by people who are now not easy to trace, and whose websites are long gone. But their work lives on. 24.5. A Website of Its Own While any good story file ought to go into the IF Archive, it's probably wise also to provide an easier-to-use home for the work, by putting up a web page and a copy of the story file on a private web host. That host should ideally be as stable as possible, so that the URL is likely to remain fixed for what might be a long period. Freeware games have a long period of viability relative to commercial games, which means that players may still be hearing about and checking out a game years after its initial release. A stable address helps everyone with links, and makes it easier for Google to direct people. Of course creating a web page involves a little design work, but tools are widely available which make this quite easy nowadays. And as we've seen, Inform can automatically generate web pages and even small mini-sites to put all the information about a story file into a tidy format. More ambitious web pages might even offer the game in a form which people can play directly through a browser. This is especially important for works meant for players who are not part of the hard-core IF community (and who therefore might be confused by a two-step interpreter-and-game-download process). There are several browser-based interpreters available, both in Java and in Flash; the state of the art changes rapidly. A good place to look for information on the latest interpreters is the ifwiki: http://ifwiki.org/index.php/Category:Interpreter 24.6. IFDB: The Interactive Fiction Database Once the story file has a home online, and a URL (that is, a web address) at which it can be found, it needs to be registered with IFDB: http://ifdb.tads.org/ the Interactive Fiction Database. Just as the IF Archive is a repository for games themselves, IFDB is a database containing information about them - titles, authors, locations, solutions, reviews, recommendation lists and more. The name IFDB echoes the Internet Movie Database (IMDB), but in some ways it is also like the iTunes Music Store. For one thing, it's a shop-window for what's new, with cover art to catch the eye. For another, some interpreters allow players to browse IFDB directly and launch new games in a single click. This kind of integration is only likely to increase, so story files unregistered on IFDB are likely to be much less visible to players of the future. Promoting IF is all about pulling in impulse players -- people who are passingly interested, but might not try the game if there is any significant work involved is setting it up. This is what IFDB is all about. IFDB is community-editable, like Wikipedia, though editors are required to create an account and log in first -- this is free, of course. A standard form is provided for creating a new record (accessible by selecting the option to add a game listing). More or less the same information that appears on Inform's library card in the Contents index needs to be copied over: there's space for the author name, game title, genre, and so on. IFDB will also ask for an IFID, a code identifying the game uniquely. Inform generates one of these automatically for each project, and it, too, is on the Library Card. It can always be found by typing VERSION into the compiled game and looking at the line that says Identification number: //[some letters and numbers]// The part between the // marks is the IFID. If there's cover art, that can also be uploaded, and good cover art makes a big difference to shop-window-appeal. The download link should give the most stable URL available. If you have not yet uploaded your game to the IF Archive, you may do so by selecting the "Upload it to the IF Archive" link instead of pressing the "Add a Link" button. The benefits of submitting your game to the IF Archive in this manner are two-fold. One, IFDB will fill in much of the information required by the IF Archive for you. Two, the link to your game will not appear until the IF Archive maintainers move it to its permanent home in the archive, at which point the download link will be automatically updated and presented on the game page. If you choose to upload your story file to the IF Archive independent of IFDB, then once the story file is safely up at its permanent home on the IF Archive, that is an ideal address to quote here. Otherwise, the URL of the work's own website is best. (Note that the IFDB entry can always be edited later, if the URL moves.) Commercial works which aren't available as free downloads can be registered on IFDB just the same, and this is almost certainly a good idea. 24.7. Competitions One very common way to get players for IF is to enter the game into an IF competition. The annual IF Competition is the most prestigious and has the widest field, but the Spring Thing, the One Room Game Competition and other events also catch people's attention. Entering a competition is a path of least effort for authors promoting their new work, because the competition organizer usually takes care of hosting and archiving submitted games, promoting the competition as a whole, collecting votes, and encouraging players to post reviews. Different contests have different arrangements. The ifwiki usually posts a list of current and upcoming competitions, as well as lists of results for those recently past, on the front page: http://www.ifwiki.org Some competitions also have their own websites, at least at the relevant times of year. All the same, there are many IF works that aren't cut out for competition release. Competitions tend to be best for short or medium-short works, because judges don't necessarily have time to play a lot of long games at once, and sometimes this is a condition of entry. It's also good for publicity to win one of the annual XYZZY Awards. All interactive fiction games released in a given year are eligible, and authors do not need to do anything to enter. As with the Oscars, though, you can't plan to win: it happens or it doesn't. 24.8. SPAG Just as major movies and books are launched along with a publicity campaign which involves getting the press interested, so it can be with IF, on a more modest scale. Probably the best option here is to try to interest the editors of the long-standing webzine SPAG, which appears quarterly and is now well past its 50th issue: http://www.sparkynet.com/spag/ If the editors bite, they may want to arrange for the new IF to be announced along with a review and write-up. This requires a little extra patience -- the release has to be timed to coincide with SPAG's publication date -- but that extra wait and effort can result in greater attention for the work. This is especially worthwhile for a major piece, one that's too large for competition entry and which has more to interest players than might first meet the eye. There are also lively webzines for the community of IF in languages other than English: for example, the excellent SPAC, which serves Spanish IF - http://spac.caad.es/ 24.9. The Gaming Avant-Garde The IF community is not the only potential audience for a work of interactive fiction. Some authors have successfully written and pitched IF to other groups -- audiences interested in a particular historical period, role-playing game universe, or web comic, for instance -- and those groups have to be reached through their own community forums and meeting places. Even if we do write material mostly meant for the existing IF community, that doesn't mean the audience has to stop there. There are a number of independent gaming websites and weblogs that feature IF reviews occasionally or regularly. These things change quickly, but at the time of writing, IF is featured with some regularity on: PlayThisThing (www.playthisthing.com): a blog devoted to critiques of independent games, which primarily focuses on works the reviewers think *are* worth playing; there are few negative reviews. There is a suggestions page for submitting review requests, and it is allowable for an author to recommend that his own game be reviewed. Not all suggestions are accepted, but many are. JayIsGames (www.jayisgames.com): a popular blog devoted to casual games, which occasionally profiles IF. JIG has also developed its own Flash interpreter for z-code games to allow the blog to host interactive fiction without requiring the casual audience to do any downloading. Experience suggests that JIG players are most interested in short IF -- serious or lighthearted, but humor goes over especially well -- and that they prefer very rigorously implemented work where a wide variety of player actions get customized replies. Small, polished gems do well here. JIG accepts game suggestions as well. The Independent Gaming Source (www.tigsource.com): occasionally publishes reviews or shorter announcements, and has even hosted an IF-writing competition. It may be worth drawing something to their attention. This is hardly a complete list of gaming blogs with an interest in interactive fiction, just a collection of the most accessible ones, so it's worth doing a little research. One way is to pick a handful of works that you think come closest to our own game in design and style, and search for reviews of those works. Where were they reviewed, and where were they well-received? Those venues might be good targets for our own production. Finally, there is a constant round of competitions for independent games in general. Unlike IF community competitions, larger indie game comps usually don't require that a game be previously unreleased, only that it have no commercial funding. Some of these competitions offer substantial prizes in cash or computing equipment; some explicitly seek text-based games. Placing as a finalist in such a competition can mean having work displayed at a gaming expo or hosted on a special wesbsite, and this will garner substantial outside press. The field of competitors will be large and serious, but that doesn't mean it's not worth giving it a try. This may all be a bit overwhelming. All the publicity options can seem like more work than we want to handle while simultaneously finishing a substantial opus. In fact, we don't have to do it all at once. One sensible approach is to release to the IF community first, and then approach the external websites later with a second or third release that puts a final polish on the game in response to player feedback. That process is even more important for indie gaming competitions. Having a release that's been polished, together with an attractive website, cover art, and maybe even some quotes from IF reviewers, can make a game look much more like a legitimate contender among semi-pro works. 24.10. The Digital Literature Community If our work is more a work of digital literature than a game, different venues are appropriate. PlayThisThing may still be interested; JayIsGames probably will not be. Instead, we might want to look at GrandTextAuto (www.grandtextauto.com): a group blog about new media and interactive story-telling, which sometimes posts announcements of interactive fiction, especially of the more literary kind. The Electronic Literature Organization (http://eliterature.org/): an organization dedicated to preserving all kinds of new media literature. They list a number of events (such as readings open to the public, new media gallery exhibits, etc.) that an IF author could participate in, and they also have a directory of electronic literature, to which we can add our own works. Digital Humanities Quarterly (http://www.noraproject.org/dhq/index.shtml): A scholarly publication, but one that looks at all aspects of digital literature, new media tie-ins for scholarship, etc. DHQ has run several articles about interactive fiction in the past, including Dennis Jerz's ground-breaking research on the writing of the first text adventure, Colossal Cave. DHQ might be open either to hosting a work or to publishing an article about it. That still leaves out a category of IF -- namely, work written for a popular reading audience, work that isn't trying to be literary but also isn't primarily game-like. There are, at the moment, no ideal venues for promoting such work (that we're aware of), but it's certainly worth pursuing. 24.11. A short concluding homily It's natural to want to make a huge splash with a game, but in the IF community, instant widespread adulation for any work is pretty uncommon. For one thing, players tend to play when they get around to it... which may be weeks, months, or even years after the initial release. Reviews trickle rather than flooding in. Appreciation builds slowly. And sometimes works that placed unspectacularly in a competition, or seemed to be overlooked in the annual XYZZY Awards, gradually come to be regarded as classics because of some pioneering technique. So it's wise (if difficult) not to judge a game's success entirely by its immediate feedback. Even after its debut, a game can often use a little care and attention if it's to reach all its potential fans -- whether that means building further releases, posting hint files or walkthroughs, developing new websites, or approaching outside reviewers. Chapter 25: Extensions 25.1. The status of extensions The range of simulation offered by Inform's model world is intentionally limited to a core of basic essentials. We could argue at the margins, and the choice of what's in and what's out is partly traditional, but most people find the model reasonable as far as it goes. Between 1993 and 2006, quite a range of "library extensions" for Inform 6 was written. Most of these extensions aimed to fill out the model by simulating other aspects of life, too: money, clothing, pourable liquids. None of these extensions was official and all of them were: it was a free-for-all, and in several cases different authors wrote rival extensions to model the same basic ideas. The development of Inform 7 was strongly influenced by this history and by the recognition that the base of rules and grammar inside a typical modern game are seldom written by a single author. They combine the standard Inform material with extensions by several third parties, together with anything specific to the game in question. Inform 7 has a more organised idea of extensions, as we shall see. But anyone is free to write an extension on any terms or for any reason. Writers may wish to use the techniques in this chapter to develop private extensions of their own, used in several projects, or to share them with associates but not more widely. But most writers of extensions do so to contribute to the Inform community, and for the satisfaction of solving a problem. Inform does not recognise anyone's approach to a particular need as "the official solution" - for instance, although the standard Inform distribution includes a copy of Locksmith by Emily Short, that is not the "official" way to make automatically unlocking doors, and anyone is welcome to try a better one. However, the Inform project does recognise some extensions as "public". Public extensions are the ones archived on the Inform website for the free use of all Inform writers. Those who wish to contribute an extension as a public one are obliged to follow a number of guidelines, which are mostly stylistic points intended to make the range of extensions easier to work with. Extension writers are asked to join in the spirit of these rules and help make the whole cooperative enterprise work harmoniously. Writers who wish to make their extensions public on the Inform website should also be clear that by doing so, they are donating their work to the community on the basis of the broadest form of Creative Commons license: that is, they retain copyright and the right to be identified as the author (and as we shall see they are automatically credited in any work of IF which uses their extension), but are giving unlimited permission to use, circulate and republish their extensions in any form, even as part of commercial works (should that arise). To publish a public extension is a public-spirited act, done for only the reward of a modest acknowledgement. If the author of an extension has not made it public, or indicated in some other way that it is free to be used without the need for permission, then it would be both polite and prudent to check with the author before publishing something which incorporates his work. 25.2. The Standard Rules When any source text is run through Inform, a secret first line is inserted, which reads: Include the Standard Rules by Graham Nelson. The "Standard Rules" file contains the definitions of the basic kinds, phrases, actions and grammar described in this documentation: for instance, it includes lines like A container is a kind of thing. ...without which Inform would be lost. Although including the Standard Rules is compulsory, it is treated internally as if it were any other "extension". What happens when an "Include" sentence is reached is that the sentence is replaced with the whole text of the file in question, often many paragraphs long. If the file has already been included, then the sentence is simply ignored. This is so that we can have two extensions, each of which needs the other: if A says to include B, and B says to include A, the result is that including one automatically includes the other, so we always get both which ever we ask for - not that there is a hideous infinite regress. 25.3. Authorship Extensions are identified by author and by name, so that a given author can produce his or her own range of extensions, and need only ensure that these are named differently from each other. If John Smith and Mary Brown each want to write an extension called "Following People", there is no conflict. The name of an extension, and of an author, should be written in Sentence Capitalisation: that is, upper case for the first letter in each word. (Inform uses this to minimise problems on machines where filenames are read with case sensitivity.) It is permitted for author names to include upper-case letters within words, as with the "G" in "Jesse McGrew". In general it is best to avoid accented or unusual letters in titles and author names, but the standard ISO Latin-1 characters should be allowed - for instance, Étude Pour La Fênetre by Françoise Gauß begins here. The author name must not start with "The", nor contain the words "by", "and" or "version", or contain punctuation, as in "John X. Doe"; the title similarly, except that "and" is permitted. Name and author's name must each be no more than 50 characters long, including any spaces between words. Authors are asked to use real names rather than cryptic handles like "ifguy", and to use genteel, plausible pseudonyms like "Emily Short" rather than, say, "Drooling Zombie" or "Team Inform". Authors are also asked to use the same author's name for all their own extensions, and (it should go without saying) not to masquerade as anybody else. Sometimes authorship is complicated. What if Mary Brown finds some Inform 6 code written by John Smith in the mid-90s, and puts an I7 gloss on it to make an I7 extension, but then Pierre Dupont translates it into French: who's the author of the result? The rule is that the person making the current, latest version is the author listed in the titling line, so we end up with ... by Pierre Dupont begins here. But Mary and John deserve their credits too: see the next section for how to give them. 25.4. A simple example extension Extensions are plain text files, and can be created with any text editor. (It is sometimes said that "there is no such thing as plain text", there being so many ways to represent exotic characters: so to be precise, an extension is a text file with the Unicode UTF-8 encoding, either with or without a BOM marker, using any of the possible forms of line-ending (Unix, Windows, Macintosh, or Unicode line divider). This is a detail which will only matter if the extension contains accented letters or other exotica.) To become available to Inform, an extension must be installed in the user's extensions folder: see Chapter 2. Extensions look very much like passages of Inform source, because except for a special introductory and concluding sentence, and one convention, that is all they are: The Ducking Action by Graham Nelson begins here. "An action for ducking one's head." Ducking is an action applying to nothing. Report ducking: say "You duck!" Understand "duck" as ducking. The Ducking Action ends here. Not a useful or interesting extension, but those few words add a whole new action and everything needed to make it work. It is Inform's ability to mix up rooms, things, kinds, grammar, phrases and rules, in more or less any order, which makes it possible for extensions to work. The introductory sentence must be placed as the only content of line 1 of the file, which must not contain comments, and has to be written in exactly the correct form. Inform checks this very carefully when performing its census of installed extensions, on each translation of the text. (In case the extension's title is a plural, we are allowed to write "begin" and "end" instead of "begins" and "ends". For instance, the last line of the standard rules is "The Standard Rules end here.") The "one convention" mentioned above is that if a double-quoted text is placed immediately after the beginning sentence (and with no intervening comments), then it is taken to be a short description of the extension's content called the "rubric". Hence the line: "An action for ducking one's head." Providing a rubric is helpful, because it enables Inform to give a meaningful listing even for an as-yet unused and unindexed extension, and because it helps the Inform website to produce better directories. Note the word "short": such text is likely to be truncated if it exceeds 500 characters. A second double-quoted text can also, optionally, be added in yet a third special starting paragraph. This is to provide additional credits to people who have contributed to this or earlier versions. For instance: The Ducking Action by Graham Nelson begins here. "An action for ducking one's head." "based on original Inform 6 code by Marc Canard" Note the typical style here: it's a phrase rather than a sentence, and neither starts with an upper-case letter nor ends with a full stop. (The additional credit is then used in documentation and also in the VERSION text of any Inform story file using the extension.) Example 438 (**): Modern Conveniences Exemplifying the kind of source we might use in writing extensions for kitchen and bathroom appliances. 25.5. Version numbering As we have seen, extensions are referred to by name and author, but they can also (optionally) be referred to by version. For instance: Include version 2 of the Ducking Action by Graham Nelson. Version 1/040426 of the Ducking Action by Graham Nelson begins here. A version number must be a whole number 1, 2, ..., 999 (version 0 is not allowed, and nor are decimal points), optionally followed by a slash '/' and then a six-figure date, in the form YYMMDD: so 040426 means 26 April 2004. A request to include version 2 of something implicitly means "version 2 or later", and similarly "version 2/040426" means version 2 with a date of 26 April 2004 or later, or else any version higher than 2. If Inform loads the extension but finds that its version is not good enough, an error is issued. Where no version number is quoted, the rule is that an unspecified version predates any numbered version. This means that the line Include the Ducking Action by Graham Nelson. will be happy with any version of the extension at all, whether numbered or not; but Include version 2 of the Ducking Action by Graham Nelson. will only accept the extension if it has a version number attached (and with that number being 2 or higher). During play of any game compiled by Inform 7, typing VERSION lists various serial numbers of the pieces of software used to make it. The list concludes with names, authors and version numbers of any extensions used. So every author whose work contributes to a game automatically gets a modest credit within it. The same list can be printed, at the discretion of the designer, using the textual substitution:

say "[the/-- list of extension credits]"
This text substitution expands to one or more lines of text crediting each of the extensions used by the current source text, along with their version numbers and authors. Extensions whose authors have chosen the "use authorial modesty" option are missed out. Example: Standard Rules version 2/090402 by Graham Nelson
If we want our extension to go uncredited - perhaps if it is a low-level enabling sort of thing, for instance - we can place the following sentence inside the definition of the extension: Use authorial modesty. The same sentence placed in the body of a source text causes all extensions by the same author as the main source text to go uncredited. In other words, if Isaac Miggins writes a source text and includes, say, Unlikely Events by Isaac Miggins, then this extension will go uncredited in the VERSION command. A complete list, undiluted by modesty, can always be obtained using:

say "[the/-- complete list of extension credits]"
This text substitution expands to one or more lines of text crediting each of the extensions used by the current source text, along with their version numbers and authors. Every extension is included, even those whose authors have opted for "use authorial modesty". Example: Standard Rules version 2/090402 by Graham Nelson Locksmith version 9 by Emily Short
25.6. Extensions and story file formats Inform compiles to several different story file formats, and in each case uses only a small part of their abilities - especially when it comes to fancy tricks with the keyboard or screen. So people may well want to write extensions which provide access to some of these tricks (like "Basic Screen Effects", included in the standard Inform distribution, but more so). Unfortunately, these tricks are very likely to fail to compile - or fail to work - on some of the possible story file formats, so the resulting extension would probably go wrong (and mysteriously wrong) for users who have chosen a different format. Inform therefore provides a way for extensions to declare the formats they are compatible with. All that is required is to add a proviso in brackets after the title is declared: Version 2 of Basic Screen Effects (for Z-Machine version 5 or 8 only) by Emily Short begins here. Other examples might be "(for Glulx only)", or "(for Z-machine only)" - which means any version of the Z-machine, even version 6. If no such proviso is given, the extension is assumed to be compatible with every story file format. Extensions are also able to include material which is only used on some story file formats and not others - in principle, this might allow the same facilities to be provided to the author whatever story file format is used, but to achieve these effects differently depending on the current Settings. The convention here is exactly like "not for release": if a heading or subheading in the source text contains a bracketed proviso, then the material under that heading (and under its dependent subheadings) will be ignored if the current story file format does not match. For example: Section 2.3G (for Glulx only) To reveal the explosion: [...the Glulx way...] Section 2.3Z (for Z-machine only) To reveal the explosion: [...the Z-machine way...] would ensure that "reveal the explosion" works nicely whichever story file format is used. Example 439 (**): Tilt 3 Displaying the card suits from our deck of cards with red and black colored unicode symbols. 25.7. Extensions can include other extensions As was mentioned earlier, the same extension is sometimes requested several times. For instance, suppose the main source text asks to include version 2 of extension X, and also to include extension Y. Suppose further that Y contains a request to include version 4 of X. We now have two different requests for X. Inform works out the minimum version number needed to satisfy these requests (in this case 4) and gives an error if the extension it actually loads turns out to be earlier. This is true even of the Standard Rules. Suppose that the Standard Rules had recently been republished in version 37, making the previously existing version 36 out of date, and that an extension is written which capitalizes on a new feature in v37. It will therefore not work if people try to use it with v36. All the extension needs to do is to say: Include version 37 of the Standard Rules by Graham Nelson. to guarantee that v37 or later will be used. If an extension does include other extensions, it should do so in a paragraph immediately following the introductory sentence, so that anyone looking at the file can see these mutual dependencies at a glance. 25.8. Extensions can interact with other extensions When one extension is being used, it's probably only one among several. A really general-purpose extension might want to behave differently depending on which other extensions are also present. This can be achieved using headings which are "for use with" (or "without") other extensions. For instance: Chapter 2a (for use with Locksmith by Emily Short) specifies that everything under this heading (and its subheadings, if any) will be ignored unless the extension Locksmith by Emily Short is included. Conversely, Chapter 2b (for use without Locksmith by Emily Short) will be ignored unless it isn't included. This allows an extension to give two variations on the same material - one if Locksmith is present, the other if not. Headings can also replace portions of extensions which have been included. For instance: Section 6 - Hacked locking (in place of Section 1 - Regular locking in Locksmith by Emily Short) places the source text under the new heading in the place of the old (which is thrown away). If there should be two or more headings of the same name in the given extension, the first is the one replaced; if two or more headings attempt to replace the same heading in the given extension, the final attempt in source text order is the one which succeeds; and finally, heading dependencies like the above are scanned in a top-down way. Thus, if we have: Chapter 2a (for use with Locksmith by Emily Short) ... Section 1 - Hacked marbles (in place of Section 4 in Marbles by Peter Wong) ... and we don't include Locksmith, then the replacement of Section 4 of Marbles is not made, because Section 1 - Hacked marbles is subordinate to the Chapter 2a heading which we've told Inform to ignore. 25.9. Extensions in the Index As soon as a project has successfully been translated, its Index is brought up to date: pages of the index record all the kinds and what they are for, all the phrases which can be used, and so on. Any kind or phrase created in an extension is automatically included. The extension's presence in the project is itself recorded - the Contents index for any project contains a brief list of all extensions used in that project, along with their authors and version numbers. For instance: Standard Rules version 1/040731 Locksmith by Emily Short Tupperware by Emily Short The Kinds index aims to give the reader a brief note of what each kind is intended for. We can provide for this by writing a sentence like so: The specification of player's holdall is "Represents a container which the player can carry around as a sort of rucksack, into which spare items are automatically stowed away." There is no need to specify the properties which apply: that is all done automatically. "Specification" is a sort of pseudo-property used just for this: we can also give specifications to kinds of value and to actions, and these are similarly used in the Index pages. Every extension has the right to its own set of headings and subheadings, independently of those used by the main source for the work or by any other extension which may be included. (So if the extension is divided into four sections and finishes on Section D, say, that doesn't mean that Section D will continue outside the extension as the main source of the game runs on.) Extensions should, of course, be written so that they never produce Problem messages, so at first sight it appears that these headings will never be outwardly visible. In fact, though, Problems do occasionally turn up in extensions, usually when the user has made a mistake, or when two inconsistent extensions are used in the same project. But more importantly, the headings in an extension are used when indexing phrases (and also actions) to group similar phrases together. For instance, the Standard Rules contain the heading: Section SR4/7 - Searching and sorting tables The half-dozen phrases defined in this section of the Standard Rules are then indexed under the subheading "Searching and sorting tables": Inform looks for a hyphen in the heading and then uses any text which follows the hyphen. (If there is no hyphen, the entire heading text is used.) If an extension contains no headings, its phrases (or actions) are indexed simply as "Miscellaneous". Finally, any phrase or variable defined immediately under a heading whose name ends in the word "unindexed" will be omitted from the Phrasebook or Contents index respectively. (That won't apply to definitions under subheadings of the heading.) This is intended so that technical apparatus used only inside the extensions can be concealed from the outside user's immediate view. Inform as it is presently constituted does not allow extensions to make fully private definitions, but this feature at least allows them to make unadvertised ones. 25.10. Extension documentation A basic mechanism for documenting extensions is built into Inform. For many extensions, this will probably do instead of a manual; for more complex ones, it should still prove a useful supplement to one. As described in Chapter 2 above, whenever an extension is used, whatever documentation it provides is also added to the main Inform documentation. Such text should be written concisely, while giving examples wherever appropriate. Stylistically, it should ideally follow the model of the main Inform documentation: just as an extension expands the standard rules, so its documentation expands this manual. "We need..." is preferred to "You need...", and so on: we're all in this together. In order to be recognised as documentation, this text should appear at the foot of the extension file, after the compulsory end sentence. The first paragraph must have exactly the following form, with a skipped line before and after: ---- DOCUMENTATION ---- For instance, the "Ducking Action" example might end: ... The Ducking Action ends here. ---- DOCUMENTATION ---- This is a modest extension, with much to be modest about. It allows us to use a new action for ducking, as in ducking the player's head (not as in ducking a witch). Ducking will do nothing unless rules are added: Instead of ducking in the Shooting Gallery, say "Too late!" ... We obtain indented code examples by beginning a line with a tab. A double indentation can be got with two tabs in a row, and so forth. (Beware: some text editors, or emailers, flatten tabs into a row of four or perhaps eight spaces each. Inform will not recognise such a line of spaces as a tab.) Note that text in square brackets should be avoided in the documentation, because that's taken as being comment matter on the extension, and omitted. Tables should be similarly indented, and should begin with the word "Table ...": the top line is taken to be the name of the table, and subsequent lines are tab-divided columns. Inform will automatically group this into a table, like so: Table of Exemplariness stellar object example galaxy "Andromeda Galaxy M31" star "Sirius" planet "Neptune" moon "Enceladus" dwarf planet "Ceres" plutino "38083 Rhadamanthus" cubewano "Easterbunny" 25.11. Examples and headings in extension documentation Extensions with very large amounts of documentation can, if the author chooses, divide the material up using headings and/or subheadings. These must be written as paragraphs exactly like so: Chapter: Avoiding Events Section: Ducking examinations and tests Inform will then typeset them to stand out, will number them automatically, and will add a table of contents at the top of the page. (For most extensions, the documentation will be short and sweet, and this would just be clutter: headings and subheadings are best used only where the text would otherwise be difficult to read.) Any extension's documentation can contain Examples, just as the main Inform documentation does: these are automatically labelled A, B, C, ... rather than given numbers, to ensure that they do not clash with the numbering used in the built-in chapters. (The labels may be helpful in writing an extension's documentation: we can write, for instance, a note such as "see Example C below".) Examples must be given last in the documentation, and there can be up to 26 of them, though most extensions will need one example at the most, and some will have none at all. Each example must begin with a paragraph exactly like so: Example: ** We Must Perform a Quirkafleeg - Ducking to avoid arrows as one proceeds east across battlements. Again, there must be a skipped line before and after. The row of asterisks must be *, **, *** or ****, just as in the main documentation, which we should follow on all points of style. The rest of the line contains the title, a hyphen, and then the description. The title should be given with Each Word except Prepositions and Similar Things Capitalized, while the description should look like a sentence, and end with a full stop. The text of the example follows, of course, and continues until the end of the file, or the next "Example:" line, whichever comes first. Each example should (normally) contain one single, complete, game, long enough to demonstrate the use of the extension and to have a little flavour to it, but not so long that the reader gets lost. It should have a title, which should match the name of the example (in the case above, "We Must Perform a Quirkafleeg"). It should conclude with a paragraph defining a test: Test me with "east / duck / east / jump / east / duck / east / rescue esmerelda". The idea is that typing one single command, TEST ME, into the resulting game should show off what the extension does. When an extension contains more than one example, they should be given in order of asterisk rating, that is, starting with the * examples, then the ** examples, and so on up. 25.12. Implications Extensions often need to define new kinds or properties, which we want to make as helpful as possible for the user. In particular, we want them not to require additional work for the author just to obtain the effect which seems only natural. For example, consider Inform's built-in "locked" property. If a door is locked, then it cannot be opened, which seems fair enough. But if the player tries to unlock the door, he might then find the following response: That doesn't seem to be something you can unlock. Which does not seem right. In real life, almost all locked items have outwardly exposed locks which it is perfectly sensible to try to unlock, given a key. The problem is that our door has the "locked" property, but not the "lockable" one. The Standard Rules solve this problem by including the following line: Something locked is usually lockable. This ensures that any door said by the author only to be "locked" will be "lockable" as well, and adds a small but worthwhile touch of realism. Such a sentence is called an "implication", as it is in the form "Condition A implies Condition B". Note that the two conditions must consist of either/or properties with or without kinds attached. Thus: A room in the Open Desert is usually lighted. will not work because "a room in the Open Desert" is a more complicated grammatical construction than, say, "lighted" or "a lighted room": it contains a relative clause. Inform can only deal with simple implications. Inform never overrides certainties with mere implications, and is cautious about allowing them to build overly long chains of argument. This is to prevent the following kind of difficulty: An open door is usually closed. A closed door is usually open. Implications work just the same for values which aren't objects, so: Colour is a kind of value. The colours are red, green and blue. A colour can be zesty or flat. A colour can be bright or dull. Red and blue are bright. Blue is flat. A bright colour is usually zesty. results in red being zesty, but blue and green being flat; blue because the source text explicitly says so (which trumps the "usually"), and green because this isn't a bright colour, so the implication doesn't arise. Implications have not been mentioned up to now since they are only really needed by extensions, but also because they can be tricky, with unforeseen consequences. We should handle them with care. 25.13. Using Inform 6 within Inform 7 To return to what was said on the first page of this documentation: Inform 7 (or I7), the current version, is not at all like Inform 6 (or I6). Internally, however, I7 works by translating the source text into an I6 program, so that in a practical sense the current version of Inform actually contains its predecessor. The final sections of this chapter show how I6 code can be mixed directly in with I7. The remaining pages will therefore make little or no sense to those who do not already use I6. But for those who do know I6 already, it would be all too easy to write highly hybridised code, constantly mixing I6 and I7. The authors of Inform hope that this will not happen: for almost all purposes, I7 is much more powerful than I6, and fails - when it has to fail - in a way more helpful to the user. Ideally, all I6 content would be confined to extensions (and this may be mandated in future releases of Inform), and even writers of extensions are asked to pare down their usage of I6 to the minimum necessary. The methods for incorporating I6 code into I7 have been designed with this in mind, that is, to encourage people to use I6 in as self-contained a way as possible: in particular to isolate the relatively few functions which need to be written in I6, and to give them natural language expression. Finally, anyone hacking with I7 for a while is likely to become curious about the Standard Rules file, and to look at the text on which the Inform world model is founded. The file is, of course, no secret, but it can be misleading. For one thing, it appears to have great freedom to set up the world model as it pleases, but in fact the I7 compiler may well crash unless certain things are done just so in the Standard Rules: they depend on each other. Moreover, the Standard Rules use a number of syntaxes which are not documented in this chapter: these are constantly being altered, and it would not be safe to imitate them. Any I6-related syntax which is not documented in this chapter may be removed or changed in effect at any time without warning, for instance in an update of Inform to fix bugs. 25.14. Defining phrases in Inform 6 The phrases described in this documentation, such as "end the story", are all defined in the Standard Rules, and are for the most part defined not in terms of other I7 phrases but instead reduced to equivalents in I6. For instance: To end the game in death: (- deadflag=3; story_complete=false; -). The notation "(-" and "-)" indicates that what comes in between is I6 code. The minus sign is supposed to be a mnemonic for the decrease from 7 to 6: later we shall use "(+" and "+)" to go back up the other way, from 6 to 7. When a phrase is defined as containing only a single command, and that command is defined using I6 - as here - it is compiled in-line. This means that the phrase "end the game in death" will always be translated as "deadflag=1;", rather than being translated into a call to a suitable function whose only statement is "deadflag=1;". This is an easy case since the wording never varies. More typical examples would be: To say (something - number): (- print {something}; -). To sort (T - table name) in (TC - table column) order: (- TableSort({T}, {TC}, 1); -). When the braced name of one of the variables in the phrase preamble appears, this is compiled to the corresponding I6 expression at the relevant position in the I6 code. So, for instance, say the capacity of the basket might be compiled to print O17_basket.capacity; because "{something}" is expanded to "capacity of the basket" (I7 code) and then translated to "O17_basket.capacity" (I6 code), which is then spliced into the original I6 definition "print {something};". Braces "{" are of course significant in I6. A real brace can be obtained by making the character following it a space, and then I7 will not attempt to read it as a request for substitution. Finally, note that while a normal I7 phrase definition can give a kind as what must be matched, e.g., To release wild tigers into (arena - a room): ... it is in general a bad idea, and will result in inefficient code, for an phrase defined using I6 to do this. Instead, if possible, match against "object", where any room, region, thing or direction will be a valid match: To release wild tigers into (arena - an object): ... Example 440 (*): Odins Making [is-are] and [it-they] say tokens that will choose appropriately based on the last object mentioned. Example 441 (***): Pink or Blue Asking the player to select a gender to begin play. 25.15. Phrases to decide in Inform 6 There are basically three forms of phrase in I7: phrases which do something, but produce no value or opinion as a result; phrases to decide whether or not something is true; and phrases to decide on a value. We have already seen examples of writing the first form in I6: To say (something - number): (- print {something}; -). Here the I6 form is required to be I6 routine code in void context, that is, it will normally be one or more statements each of which ends in a semicolon (unless there are braced code blocks present). In this case, we have just one I6 statement, ending in a semicolon. An example of a phrase to decide whether something is true would be: To decide whether in darkness: (- (location==thedark) -). Here the I6 code providing the definition must be a valid I6 condition, and be in round brackets, but there is no semicolon. Lastly, an example of a phrase to decide on a value: To decide which number is the hours part of (t - time): (- ({t}/60) -). Again, this is a value in I6 as well: no semicolon. It is probably safest to place the value in round brackets. 25.16. Handling phrase options The Standard Rules use the Inform list-writer with the following definition, which shows how a much more complicated I6 routine can be given a natural-language expression. To list the contents of (O - an object), with newlines, indented, giving inventory information, as a sentence, including contents, including all contents, tersely, giving brief inventory information, using the definite article, listing marked items only, prefacing with is/are, not listing concealed items, suppressing all articles and/or with extra indentation: (- I7WriteListFrom(child({O}), {phrase options}); -). This can be used by, say: list the contents of O, as a sentence, using the definite article "{phrase options}" is a special substitution: it is a bitmap which assigns the given options one bit each, starting with the least significant bit for the first-mentioned option ("with newlines" above) and going up to the most significant bit for the last ("not listing concealed items"). 25.17. Making and testing use options Use options (see Chapter 2 above) manifest themselves in the I6 code generated by I7 as constants which are either defined, or not. For instance, the "use American dialect" option results in the constant DIALECT_US being defined, a constant which otherwise would not be. Some use options define the constant as a particular value, others simply define it (so that I6 gives this constant the value 0). New use options can be created as in the following examples, which are found in the Standard Rules: Use American dialect translates as (- Constant DIALECT_US; -). Use full-length room descriptions translates as (- Constant I7_LOOKMODE = 2; -). Most Inform users will not need to test whether a use option is currently set: after all, they will know whether or not their own game uses American dialect. But an extension does not know what use options apply in the game which is using it. An extension which needs to print a list, using its own formatting, might want to know whether "use serial comma" is set. Or it might want to speak differently in American dialect. To test for American dialect, we should ideally not use I6 to look for the constant DIALECT_US using #ifdef: there is no guarantee that this constant will not be renamed at some point. Instead we can perform the test directly in I7: if the American dialect option is active, ... and similarly for all other named use options. The adjectives "active" and "inactive" have the obvious meanings for use options. This means it's possible to describe the current options like so: say "We're currently using: [list of active use options]."; The result might be, say, We're currently using: dynamic memory allocation option [8192], maximum indexed text length option [1024], maximum things understood at once option [100], American dialect option and fast route-finding option. This may be useful for testing purposes. The former condition "using O", true if the option O is active, false if not, has not yet been withdrawn but is now deprecated, and may be removed in future builds, since it is redundant and less flexible; please write "if O is active" instead of "if using O". Use options can also allow the writer to raise certain maximum values. If we write an extension which needs some I6 array, say, and therefore has some limitation - for instance a footnotes presenter which can handle at most 100 footnotes before its array space runs out - it would obviously be cleaner to allow this maximum to be raised. We can set this up like so: Use maximum presented footnotes of at least 100 translates as (- Constant MAX_PRESENTED_FOOTNOTES = {N}; -). With such a definition, the number given is the default value, and the I6 source is included whether or not anybody uses the option: the default value being given if nobody does. The text "{N}" is replaced with the value. So the above definition normally results in this being defined: Constant MAX_PRESENTED_FOOTNOTES = 100; but if the user writes Use maximum presented footnotes of at least 350. then instead the I6 inclusion becomes: Constant MAX_PRESENTED_FOOTNOTES = 350; The I6 constant MAX_PRESENTED_FOOTNOTES can then be used as the size of an array, for instance. (Beta release note) Previous builds allowed:

if using the/-- (use option):
This condition is now deprecated. It duplicates the effect of: if ... is active, ...
25.18. Longer extracts of Inform 6 code Whole routines, object and class definitions (or any other directives) can be pasted in wholesale using sentences like so: Include (- [ MyInform6Routine a b; return a*b; ]; -). Such inclusions are pasted into the final compiled code at the end of the file, after the I6 grammar has been declared. In such extracts, we sometimes need to refer to objects, variables or values which can't be described using I6: or rather, which can be described, but we don't know how. To this end, any text in an inclusion written in "(+" and "+)" parentheses is treated as an I7 value, and compiled accordingly, with all type-checking waived for the occasion. For instance: Include (- Global my_global = (+ the tartan rucksack +); -). Here "the tartan rucksack" is translated into "O18_tartan_rucksack", or something similar: the I6 object created to represent the rucksack. Thus the actual line of code produced is Global my_global = O18_tartan_rucksack; The material between "(+" and "+)" is generally treated as a value, and thus compiles to the I6 form of that value. But it could also be a property name, which compiles to the I6 form in question, or a defined adjective, which compiles to the name of the routine to call which tests whether that adjective is true. Two warnings. The material in "(-" and "-)" is called template code, and it is not quite treated as literal. That means certain characters cause Inform to react: 1. Beware of accidental "(+" usage - for instance, Include (- [ MyCleverLoop i; for (++i; i<10; i++) print i; ]; -). looks reasonable, but contains "(+" and "+)". Spaces around the first "++" would have been enough to avoid this one; "+)" is only significant where it follows a "(+". 2. Beware of placing an "@" character in the first column, that is, immediately following a new line. (In template code this marks off paragraph divisions.) So for instance, Include (- [ Set_Stream ret; @glk 67 ret; ]; -). is tripped up by the Glulx assembly language opcode "@glk" because this occurs in column 1. Indenting it with a little space or a tab is enough to avoid the problem. Example 442 (*): Status line with centered text, the hard way A status line which has only the name of the location, centered. 25.19. Primitive Inform 6 declarations of rules By writing a sentence like this: The underground rule translates into I6 as "UNDERGROUND_R". we create a new rule, the "underground rule", and also notify Inform that it will have no definition as I7 source text: instead, it will be provided as an I6 routine called "UNDERGROUND_R". We can define this with an Include like so: Include (- [ UNDERGROUND_R; if (real_location hasnt light) { RulebookSucceeds(); rtrue; } rfalse; ]; -). The rule should return false if it wants to make no decision, but call either RulebookSucceeds or RulebookFails and return true if it does. These routines can optionally take an argument: which will be the return value from the rulebook. Note that UNDERGROUND_R itself has no arguments. In the case of an action based rulebook, the I6 variables noun, second and actor can be referred to, while for a value based rulebook the parameter is stored in the I6 global variable parameter_object (which is not necessarily an object, in spite of the name). We can put this rule into a rulebook in the same way that any named rule can be: The underground rule is listed in the spot danger rules. 25.20. Inform 6 objects and classes As might be expected, I7 compiles an I6 class for each kind, and an I6 object for each of its own objects. We can meddle with its compilation process here using a further refinement of Include. For instance, suppose we want the I6 class definition for things to come out containing a property like this: Class K2_thing ... with marmalade_jar_size 6, ... How to arrange this? One way is to create an ordinary I7 property, like so: A thing has a number called marmalade jar size. The marmalade jar size of a thing is usually 6. The marmalade jar size property translates into I6 as "marmalade_jar_size". (Without that last sentence, the property won't get any familiar name.) But sometimes we need more, and want to actually write new material to go into the definition. This can be done like so: Include (- with before [; Go: return 1; ], -) when defining a vehicle. This glues in a new property to the class compiled to represent the I7 kind "vehicle". (See the DM4 for why. However, since the entire actions machinery is different in the I7 world, note that "after", "react_before" and "react_after" no longer have any effect, and nor does "before" for rooms.) And similarly: Include (- has my_funny_attribute, -) when defining the hot air balloon. If we need a particular I7 object or kind to end up with a particular I6 name, we can write: The whatsit object translates into I6 as "whatsit". The thingummy kind translates into I6 as "thingummy_class". 25.21. Inform 6 variables, properties, actions, and attributes I7's variables are usually compiled as entries in an array rather than as I6 variables. However, we can instead tell Inform to use an existing I6 variable (either one that we declare ourselves, or one in the I6 template layer). For example: Room description style is a kind of value. The room description styles are Brief, Verbose and Superbrief. The current room description style is a room description style that varies. The current room description style variable translates into I6 as "lookmode". I7's properties are compiled sometimes as I6 properties, sometimes as I6 attributes, sometimes as bits in a bitmap somewhere. However, we can override I7 by telling it that one of its property names is equivalent to an already-existing I6 property or attribute: if so then I7 will use that name and will not compile any directive to create it. For example: The switched on property translates into I6 as "on". The initial appearance property translates into I6 as "initial". We do not need to translate "switched off", the opposite to "switched on": I7 will now compile this to "~on". Lastly, actions can also be translated (though it's usually better to translate their rules instead and invent new I7 actions covering them): The unlocking it with action translates into I6 as "Unlock". 25.22. Inform 6 Understand tokens The parser which deciphers the player's typed commands is written in I6, and many of the basic tokens of Understand grammar are implemented as "general parsing routines" (GPRs), the specification of which is described fully in the Inform 6 Designer's Manual. I7 translates much of the source text's Understand grammar into GPRs, and once again we can bypass this process and supply an Understand token directly as an I6 GPR. For example: The Understand token squiggle translates into I6 as "SQUIGGLE_TOKEN". We then have to include a routine of that name into I7's output using the "Include" instruction, on which more later. This creates a token "[squiggle]"; so for instance if the source text contains: Understand "copy [squiggle]" as ... then Inform would parse the command COPY FIGURE EIGHT by calling the SQUIGGLE_TOKEN routine as a GPR with the word marker at 2, that is, at the word FIGURE. As always, this should be done only where there seems no better way, or where speed is very important. For any fairly simple range of possibilities, it's better to use the techniques in the Understand chapter, or to use unit specifications. 25.23. Inform 6 adjectives There are three ways to specify that an adjective is defined at the I6 level. For example: Definition: a number is prime rather than composite if I6 routine "PRIMALITY_TEST" says so (it is greater than 1 and is divisible only by itself and 1). Inform now actually tests if a number N is prime by calling PRIMALITY_TEST(N), and it assumes that we have also included such a routine in the output. The routine is expected to return true or false accordingly. The text in brackets does nothing functional, but is the text used in the Lexicon dictionary part of the Phrasebook index for the user's benefit; it should be a brief definition. Extension authors are asked to provide these little definitions, so that their users won't be confused by blank lexicon entries. The second way makes a more capable adjective, since it can not only be tested, but also made true or false using "now". For example: Definition: a scene is crucial if I6 routine "SceneCrucial" makes it so (it is essential to winning). The difference here is "makes it so", not "says so", and as this implies, the routine has more power. "SceneCrucial" is called with two arguments: SceneCrucial(S, -1) tests whether the scene is crucial or not and returns true or false; SceneCrucial(S, true) must make it true; and SceneCrucial(S, false) must make it false. Another useful difference is that if the kind of value is one which is stored in block form (e.g. for an adjective applying to indexed text), the routine is given a pointer to the block, not a fresh copy. A third way to define an adjective, which should be used only if speed is exceptionally important, is to provide a "schema" - a sort of I6 macro, like those provided by the C preprocessor. For example: Definition: a rulebook is exciting if I6 condition "excitement_array-->(*1)==1" says so (it is really wild). The escape "*1" is expanded to the value on which the adjective is being tested. (This is usually faster than calling a routine, but in case of side-effects, the "*1" should occur only once in the condition, just as with a C macro.) To repeat: if in doubt, use the I6 routine method above. 25.24. Naming Unicode characters Inform allows the Unicode characters to be identified either with a decimal number or by name, but it has none of the character names built-in, and for efficiency reasons it only learns them when necessary. Users normally teach these names to Inform by including one of the extensions "Unicode Character Names" or "Unicode Full Character Names", which consist of many hundreds of sentences like so: anticlockwise open circle arrow translates into Unicode as 8634. Nothing restricts this usage to those extensions. 25.25. The template layer When Go is clicked, Inform translates the I7 source text into I6 code, but the directly translated code could not survive on its own: it needs a large body of supporting code, also written in I6, to sustain it. (Just as a program like iTunes or Firefox cannot run on a bare machine, but needs an operating system already up and running to support it.) Until 2008, this supporting code was provided by the I6 library, that is, the standard distribution of useful I6 code supplied with distributions of Inform 6. However, the supporting code is now generated from a collection of about 35 "segments" of I6 code which together make up "the template layer". The reason for the term "template" is that the segments are not quite directly copied into I7's output, but instead act as templates from which I7 generates code - the final output contains variations according to what the original source text needs. (For instance, if the original source text never uses indexed text, lists or stored actions, then the code and arrays needed to maintain the memory heap are omitted, making for a smaller final story file which will run in smaller interpreters.) Each segment has its own name, which looks like a leafname plus the ".i6t" filename extension (which stands for "I6 template"). Internally, a segment is itself divided up into named parts. For instance, the segment "Relations.i6t" contains a part called "Symmetric One To One Relations" which provides I6 routines for changing and testing such relations. There are more than 600 named parts across the template as a whole; it is quite a large program. An annotated, typeset version of the template - amounting to a roughly 500-page book - is available for download from the Inform website. The most powerful use of "Include" allows code to included before, instead of or after any named part or segment in the template. For example: Include (- ... -) before "Relations.i6t". Include (- ... -) instead of "Relations.i6t". Include (- ... -) after "Symmetric One To One Relations" in "Relations.i6t". Multiple such inclusions can be made for the same segment or part. If so, all will take effect in the case of "before" or "after", but for "instead of" only the most recent one takes effect. Inclusions requested before, or after, a segment or part which has been replaced with "instead of" will take effect and appear before or after the code which appears instead of it. The pre-2008 syntax Include (- ... -) before the library. has been withdrawn; the new syntax Include (- ... -) after "Definitions.i6t". should have the same effect. Template files are not written in literal I6, but in a marked-up, annotated form of I6 which has special transcription commands embedded into it. These commands should absolutely not be used except in the built-in template files, with one exception: {-segment:Flowers.i6t} places the whole of the template file "Flowers.i6t" in this position. The built-in template does not of course contain "Flowers.i6t", but Inform allows the optional "I6T" subfolder of the "Materials" folder of a project to hold additional or replacement template files. Thus the project "Botanic Gardens.inform" might store: Botanic Gardens Materials/I6T/Flowers.i6t It could even contain: Botanic Gardens Materials/I6T/Relations.i6t in which case this would automatically be used instead of the built-in copy of "Relations.i6t", without any change to the I7 source text being needed. In this way, projects can (if they need to) use partly or entirely customised templates. One application of this might allow for chunks of I6 code generated by external utilities - Perl scripts, lex and yacc, or other code generators - by compiling those to suitable template files in Materials/I6T and then using an inclusion like Include (- {-segment:MyStuff.i6t} -). in the I7 source text. Template hacking, as it's called, is a last resort. If there is any way to achieve the same ends by writing ordinary I7 source text, then that will always be better. If it is possible to write "Include (- ... -)" without mentioning any segment or part, that's much to be preferred, because it has more chance of continuing to work into the future when the template might have been rewritten. 25.26. Translating the language of play The "language of play" is the natural language used to communicate with the player at run-time: this is normally English. That means that it is difficult to write, say, Spanish-language IF using Inform 7, though heroic work by the Spanish IF community has overcome this. Inform 6 provided for translation by isolating its linguistic code in a part of the I6 library called the "language definition file", which was normally "English.h". Translations were gradually made to most major European languages, resulting in alternative language definition files called "French.h", "Italian.h" and so on. Full details on how to write a language definition file were given in the Translations chapter of the DM4, that is, the fourth edition of the Inform 6 Designer's Manual. In I7 the system is different. We use the template, not a library. Instead of providing a language definition file such as "French.h", a translator should create an extension called something like "French by Jacques Mensonge". (The language should be named in English, so "French by ...", not "Français by ...") This extension should then contain the same material as an I6 language definition file, but put in place using template hacking (see the previous section). As an example, the extension "English by David Fisher" is supplied with I7: using it has no effect because the language of play is already English, of course, so it is provided only as a model to copy. Translators will find that there are now more numbered messages than in I6, because the template includes messages which did not exist in the I6 library. (All of this is very much a work in progress. The authors of Inform hope to make translations easier in future builds: the features introduced in April 2008 are only a start.) 25.27. Segmented substitutions A "segmented" substitution is a syntax where text is placed between two or more different text substitutions. Examples include: "This hotel is [if the player is female]just awful[otherwise]basic[end if]." "Annie [one of]dances[or]sulks[or]hangs out at Remo's[at random]." To create such syntaxes, it is not enough just to define how each expands into I6 code: for one thing we may need to know about the later terms in order to expand the earlier ones, which is normally impossible, and for another thing, the individual text substitutions mean nothing in isolation. For instance, Inform produces a problem if the following is tried: "The hotel [at random] is on fire." because "[at random]" is only legal when closing a "[one of] ..." construction. But if "[at random]" had been defined as just another text substitution, Inform would not have been able to detect such problems. Inform therefore allows us to mark text substitutions as being any of three special kinds: beginning, in the middle of, or ending a segmented substitution. There can be any number of alternative forms for each of these three variants. The syntax policed is that (a) Any usage must lie entirely within a single say or piece of text. (b) It must begin with exactly one of the substitutions marked as "beginning". (c) It can contain any number, including none, of the substitutions marked as "middle" (if there are any). (d) It must end with exactly one of the substitutions marked as "ending". A simple example: To say emphasis on -- beginning say_emphasis_on: (- style underline; -). To say emphasis off -- ending say_emphasis_on: (- style roman; -). This creates "[emphasis on]" and "[emphasis off]" such that they can only be used as a pair. The keyword "say_emphasis_on", which must be a valid I6 identifier (and hence a single word), is never seen by the user: it is simply an ID token so that Inform can identify the construction to which these belong. (We recommend that anybody creating such constructions should choose an ID token which consists of the construction's name but with underscores in place of spaces: this means that the namespace for ID tokens will only clash if the primary definitions would have clashed in any case.) Example 443 (*): Chanel Version 1 Making paired italic and boldface tags like those used by HTML for web pages. 25.28. Invocation labels, counters and storage The process of expanding the I6 code which represents a phrase is called "invocation". As we have seen, when a phrase is defined using a single piece of I6 code, invocation consists of copying out that I6 code, except that tokens in braces "{thus}" are replaced: To say (something - number): (- print {something}; -). Ordinarily the only token names allowed are those matching up with names in the prototype, as here, but we have already seen one special syntax: "{phrase options}", which expands as a bitmap of the options chosen. And in fact the invocation language is larger still, as a skim through the Standard Rules will show. The notes below deliberately cover only some of its features: those which are likely to remain part of the permanent design of Inform, and which are adaptable to many uses. Please do not use any of the undocumented invocation syntaxes: they change frequently, without notice or even mention in the change log. The first special syntaxes are textual tricks. {-delete} deletes the most recent character in the I6 expansion of the phrase so far. {-erase} erases the I6 expansion of the phrase so far. {-open-brace} and {-close-brace} produce literal "{" and "}" characters. The following: {-counter:NAME} {-advance-counter:NAME} {-zero-counter:NAME} {-allocate-storage:NAME} create (if one does not already exist) a counter called NAME. This is initially zero, and can be reset back to zero using "{-zero-counter:NAME}", which expands into no text. The token "{-counter:NAME}" expands into the current value of the counter, as a literal decimal number. The token "{-advance-counter:NAME}" does the same, but then also increases it by one. Finally, the token "{-allocate-storage:NAME}" expands to nothing, but tells Inform to create an "-->" array called "I7_ST_NAME" which includes entries from 0 up to the final value of the NAME counter. This allows each instance in the source text of a given phrase to have both (i) a unique ID number for that invocation, and (ii) its own word of run-time storage, which can allow it to have a state preserved in between times when it is executed. For example: To say once only -- beginning say_once_only: (- {-allocate-storage:say_once_only}if (I7_ST_say_once_only-->{-counter:say_once_only} == false) {-open-brace} I7_ST_say_once_only-->{-advance-counter:say_once_only} = true; -). To say end once only -- ending say_once_only: (- {-close-brace} -). To complete the tools available for defining a segmented substitution, we need a way for the definition of the head to know about the middle segments and the tail: When invoking either the head or the tail, {-segment-count} expands to the literal decimal number of pieces of text in between the two, which is always one more than the number of middle segments, since the text comes in between the segments. When invoking any middle segment, {-segment-count} expands to the number of pieces of text so far -- thus it expands to 1 on the first middle segment invoked, 2 on the next, and so on. Lastly {-final-segment-marker} expands to the I6 identifier which marks the end segment, or to I6_NULL if the end segment has no marker. The idea of markers is to enable the head's definition to know which of a number of choices has been used for the tail, supposing that this is a construction with a variety of legal endings. For example: To say emphasise -- beginning say_emphasise: (- style {-final-segment-marker}; -). To say with italics -- ending say_emphasise with marker underline: (- style roman; -). To say with fixed space type -- ending say_emphasise with marker fixed: (- style roman; -). The markers used for the tails here are "underline" and "fixed", and when the head is invoked, the marker for its tail is expanded into the argument of I6's "style" statement. The examples above are all to do with segmented substitutions, which is where they are most useful, but most of the syntaxes above work equally well for ordinary "To..." phrase definitions. 25.29. To say one of Many of the invocation syntaxes described in the previous section are used in the definition by the Standard Rules of the "[one of] ... [or] ... [purely at random]" construction, so it makes a good example of how they can be used. First, this is a segmented substitution with a single possible beginning ("[one of]"), a single possible middle ("[or]") but a choice of many possible endings. Almost everything is compiled by the invocation of the beginning: To say one of -- beginning say_one_of: (- {-allocate-storage:say_one_of}I7_ST_say_one_of-->{-counter:say_one_of} = {-final-segment-marker}(I7_ST_say_one_of-->{-counter:say_one_of}, {-segment-count}); switch((I7_ST_say_one_of-->{-advance-counter:say_one_of})%({-segment-count}+1) - 1) { 0: -). To say or -- continuing say_one_of: (- {-segment-count}: -). To say purely at random -- ending say_one_of with marker I7_SOO_PAR: (- {-close-brace} -). The 3rd invocation of this (say) might compile the following: I7_ST_say_one_of-->2 = I7_SOO_PAR(I7_ST_say_one_of-->2, 4); switch((I7_ST_say_one_of-->2)%5 - 1) { 0: ... first text ... 1: ... second text ... 2: ... third text ... 3: ... fourth text ... } First, we notified Inform that it needs to allocate an array (I7_ST_say_one_of) providing storage associated with the counter "say_one_of". This we used to count off individual invocations of "[one of]", so that each would have its own word of storage - for the 3rd invocation, I7_ST_say_one_of-->2. We then call a state-changing routine, in this case I7_SOO_PAR, which is allowed to know the previous state and also the number of options available, and which returns the new state. The state is supposed to be the option chosen last time, but that means that there are not 4, but 5 possibilities: 0 for "there was no last time", then 1 to 4 for the possible outcomes. We reduce the state mod 5 to obtain the decision this time, and subtract 1 because it happens to be convenient to make the switch statement run from 0 to 3 rather than 1 to 4. (The reason we reduce the state mod 5 is to allow the state-changer to squirrel away secret information in the upper bits of the state, if it wants to. Note that subtracting one means that the switch value might be -1, which results in no text being printed: thus if the state-changer chooses 0, it can decide on none of the above.) In this design, the marker attached to the choice of ending substitution is the name of the I6 state-changer: here is the I7_SOO_PAR routine. [ I7_SOO_PAR oldval count; if (count <= 1) return count; return random(count); ]; As it happens, this ignores the old value: after all, it is meant to be purely at random, and nothing could be less pure than taking the last outcome into consideration when choosing the next. Note that the counter say_one_of is advanced in invocation of the head. It might seem that the tidier design, somehow, would be to advance the counter in the invocation of the tails, but this is not a good idea. In general it is not safe to assume that the counter will have the same value when the tail is invoked that it had when the head was invoked, because segmented say constructions can legally be nested in Inform strings. Because of this, it is best to deal with a counter entirely in a single invocation, either of the beginning or the ending. Because "[one of] ... [or] ..." is such a useful construction - switching between alternative forms of text, which writers of IF very often do - the above implementation is intentionally left open for new endings to be added, and the examples below show how easily this can be done. Example 444 (*): Blink Making a "by atmosphere" token, allowing us to design our own text variations such as "[one of]normal[or]gloomy[or]scary[by atmosphere]". Example 445 (**): Uncommon Ground Making a "by viewpoint" token, allowing us to design our own text variations such as "[show to yourself]quaint[to Lolita]thrilling[to everyone else]squalid[end show]" depending on the identity of the player at the moment. Chapter 26: What's New in Inform? 26.1. Where to find new developments Inform is a project under active development, both by its original authors and by users who contribute extensions. Besides that, it belongs to an ecosystem of related tools and projects, and they develop, too. - New extensions are posted on the Inform website at: www.inform7.com An RSS feed allows most modern Web browsers to keep track of developments since the last time this catalogue was visited. - New works published by authors using Inform are often announced at the IFDB (ifdb.tads.org), and/or by posts to www.intfiction.org/forum - New builds of Inform are identified by four-character codes: number, letter, number, number. They are posted on the Inform website (address above), usually once every month or two, and are accompanied by a detailed if rather technical change log. The remaining sections of this chapter give details of the changes in each build since 4S08, the first build considered solid enough for regular rather than experimental use: at the foot of each section the change log is reproduced verbatim in plain text, but the summary and links at the top are probably more useful. - Interpreters to play story files of the kind produced by Inform (and others) are also updated, but this is work going on independently of the Inform project as such. 26.2. What's new in build 6E59 (June 2010) (Image apr10.jpg here) As this release was being prepared, the world's largest census was taken, in India; the Eyjafjallajökull volcano in Iceland cut off air routes to Europe; in Ireland, pubs in Limerick opened on Good Friday, and a grey seal which had escaped from London Zoo was found in the seaside town of Skerries; element 117, ununseptium, was created inside atomic reactors; the Vatican declared that the Turin Shroud was not a forgery, but a mystery beyond human artistry; Lactococcus lactis became Wisconsin's official State Microbe following the passing of Assembly Bill 556 (Wisconsin's State Dance, incidentally, is the polka); Lady Gaga became the first singer to break one billion plays on YouTube, while Rukidi IV of Toro came of age and inherited his kingdom; and Cambridge had its revenge in the 156th Boat Race, defeating Oxford. In the world of Inform, the Release mechanism was improved, with better feedback and a new ability to generate websites in which the project can be played in-browser. The system of kinds was made much more flexible and expressive, and phrase definitions gained in power as a result. A new chapter on Advanced Phrases was added to the manual, covering functional and generic programming. Properties, assemblies and relations were all reworked to be applicable much more consistently across the whole range of values, rather than being restricted only to objects, simplifying the language. Limits on the lengths of names of relations, verbs, prepositions, and directions were all lifted. The documentation and the Phrasebook index were revised and harmonised. (-See A playable web page for how to release a project as a website which includes a version of the story file which plays inside the visitor's web browser.) (-See Generic phrases for writing generic-programming-style definitions of phrases.) (-See Map, filter and reduce for performing functional-programming-style computations on whole lists of values at once.) (-See New kinds for how to rearrange the built-in hierarchy of kinds.) (-See The showme phrase for the convenient new "showme" phrase.) (-See Default values of kinds for how to access the default value of any named kind.) (-See Relations involving values for how to make dynamic relations on even unbounded kinds like numbers and texts.) (-See Relations as values in their own right for handling relations abstractly.) (-See Temporary relations for creating relations as temporary data structures to hold calculational results.) (-See Basis of a rulebook for having rulebooks based on values of any kind.) (-See Rulebooks producing values for having rulebooks produce values of any kind.) (-See Adding and removing rows for new ways to blank out columns from tables, or the entire contents of a table.) (-See New activities for having activities on values of any kind.) (-See Descriptions as values for using descriptions of any kind as values.) (-See Assemblies and body parts for using assemblies to create values other than objects.) (-See Names made in assembly for giving assembled objects or values a better variety of names.) (-See Implications for writing implications about values other than objects.) (-See {Defining adjectives for values} for defining adjectives for single named values.) (-See Creating a scene for the new description property for a scene.) (-See Creating a scene for writing rules about when families of scenes begin or end.) (-See Removing things from play for using "now" with the adjectives "on-stage" and "off-stage".) (-See Going by, going through, going with for writing rules about "exiting from" something.) (-See Text with random alternatives for three new forms of "[one of]...".) (-See Plural assertions for better pluralisation of nouns.) (-See Irregular English verbs for better past participles of verbs.) (-See Deciding whether all includes for new rules on TAKE ALL.) (-See Administering classroom use for adding test and release instructions to the Options.txt configuration file.) (-See Use options for new use options on VERBOSE, BRIEF and SUPERBRIEF room description style.) (-See Inform 6 adjectives for making low-level adjectives which can be asserted with "now" as well as being tested.) (See example "Entrevaux") (See example "Wainwright Acts") (See example "Number Study") (See example "For Demonstration Purposes") (See example "The Undertomb 2") (See example "Finality") (See example "Pot of Petunias") (See example "Unblinking") 26.3. What's new in build 5Z71 (April 2009) (Image apr09.jpg here) As this release was being prepared, the Indian Ocean island of Mayotte voted to rejoin France, which in turn rejoined NATO; Sweden, Vermont and Iowa legalised gay marriage; Fermilab discovered the Y(4140) particle, composed (some said) of charm and anticharm; the Proctor and Gamble soap opera "Guiding Light" was cancelled after 72 years of family struggles, uplifting sermons, and the legendary Reva, twice believed dead but in fact an amnesiac taken in by the Amish who returned to find her husband living with a clone of her called Dolly, who in remorse took her own life with aging serum, leaving Reva free to become a San Cristobelian Queen and travel in time, and... so on; Oxford, with its heaviest rowing crew in centuries, won the annual Boat Race against Cambridge; and Barack Obama's first hundred days coincided with a hundred days of hair-tearing by the makers of the new Inform website. In the world of Inform, miscellaneous benefits came out of a substantial internal reform in logic and the handling of kinds of value. Many of those lifted niggling restrictions - see the full change log for details. Build 5Z71 uses around a third as much memory as 5U92, does much less file-handling, is a little faster, and can handle projects unlimited in size. Dimensional checking became much more flexible, allowing Inform authors to model the world with quantitative physics, and a new built-in extension, "Metric Units by Graham Nelson", defines all the kinds of value needed. Equations, imitating those in books and papers, were added to the language. The release mechanism was also rewritten, allowing much better CSS-friendly websites to be produced by the Release button. The Recipe Book was expanded and rewritten in its coverage of actions and commands. Lastly but most visibly, the Index was redesigned and the Problem messages relaid to incorporate links to relevant documentation. All 132 issues arising from bug reports since build 5U92 were closed out. (-See Equations for defining and solving numerical equations.) (-See Multiple notations for the ability to provide differently scaled ways to write numerical quantities - for instance, to provide millimeters and kilometers as well as meters when talking about lengths.) (-See The Metric Units extension for handy definitions of length, mass, elapsed time, electric current, temperature, luminosity, angle, frequency, force, energy, pressure, power, electric charge, voltage, luminance, area, volume, velocity, acceleration, momentum, density, heat capacity, specific heat capacity.) (-See Named notations for the ability to say numerical quantities in different ways - for instance, in metric or Imperial units.) (-See Numbers for the ability to round any numerical quantity, not just times of day, and for square and cube roots.) (-See Adjacent rooms and routes through the map for a new "the door north of the Garden" syntax, like the existing "the room north of the Garden" one.) (-See Duplicates for the new "maximum things understood at once" use option, which improves performance if any room has to contain, say, 100 or more duplicate objects at once.) (-See Website templates for creating new designs for Release websites which incorporate CSS.) (-See Administering classroom use for a couple of low-level features to help teachers setting up Inform for a whole class.) (-See Advanced website templates for new options accordingly.) (See example "Hatless") (See example "Oyster Wide Shut") (See example "Slogar's Revenge") (See example "The Facts Were These") (See example "The Speed of Thought") (See example "Whither?") (See example "Widget Enterprises") 26.4. What's new in build 5U92 (September 2008) (Image sep08.jpg here) As this release was being prepared, King Tupou V of Tonga was crowned, but Nepal became a Republic; climbers were lost to avalanches on K2 and Mont Blanc; Australia became perplexed at winning fewer Olympic medals than Great Britain; the most wanted man in Greece, who had escaped from prison by helicopter, was recaptured; a 50-foot spider spent a week crawling at 2 mph across the Liverpool skyline, spraying random passers-by with water; and many journalists had to learn how to spell "Ossetia" at a time when they would rather have been watching the sports channels. In the world of Inform, a set of related improvements was made to the way adjectives, nouns and verbs combine in descriptions. This lifted many restrictions which made talking about values less flexible than talking about objects, and showed the language gradually becoming more general. In addition, directions could now be created freely. All 110 issues arising from bug reports since build 5T18 were closed out. (-See Conditions of things for creating more than one condition for the same thing, and for giving them better names.) (-See Using new kinds of value in properties for making either/or and value properties for values.) (-See During scenes for some benefits of this applying to scenes, in particular.) (-See Defining new adjectives for defining the opposite of an adjective at the same time as the original.) (-See {Defining adjectives for values} for examples of defined adjectives applying to values, and for the built-in adjectives positive, negative, even, odd, empty and non-empty.) (-See Counting the number of things for counting the number of values matching some description.) (-See Repeat running through for repeating through the values matching some description.) (-See Lists of values matching a description for using "list of..." to bring together all values matching some description.) (-See Existence and there for using "there is" or "there are" to talk about whether objects or values exist.) (-See Directions for much improved facilities for creating new directions, like CLOCKWISE, STARBOARD or NNE.) (-See Understanding kinds of value for the new Understand token "[a time period]", which matches text such as 20 MINUTES or AN HOUR instead of specific times of day like MIDNIGHT or 11:24 AM.) (-See Blank rows for the adjectives "empty" and "non-empty" as applied to tables.) (-See New rulebooks for the adjectives "empty" and "non-empty" as applied to rulebooks.) (-See New activities for the adjectives "empty" and "non-empty" as applied to activities.) (-See Lists and entries for the adjectives "empty" and "non-empty" as applied to lists.) (-See Inform 6 adjectives for low-level ways to define new adjectives based on I6 code rather than I7 source text.) (-See Inform 6 Understand tokens for a new low-level way to add an I6 general parsing routine as a token of Understand grammar.) (See example "Bowler Hats and Baby Geese") (See example "Elsie") (See example "Extra Supplies") (See example "Fabrication") (See example "North by Northwest") (See example "Pizza Prince") (See example "Versailles") (See example "The World of Charles S. Roberts") 26.5. What's new in build 5T18 (April 2008) (Image apr08.jpg here) As this release was being prepared, the Grand Canyon was deliberately flooded, while Sweden's largest lake was lowered by 15cm; in London, Heathrow Terminal 5's state-of-the-art automated baggage system went live; gold prices broke £500 per troy ounce, while Pernod Ricard bought Absolut Vodka for $9 billion; in London, Heathrow Terminal 5's state-of-the-art automated baggage system began to fail, with many cancellations; Vietnam banned pet hamsters; in Nashville, King Crimson began recording again, but in Princeton our greatest translator of Homer, Robert Fagles, died; and in Milan, 15,000 items of lost luggage arrived from Heathrow Terminal 5's state-of-the-art automated baggage system, so that they could be sorted by human beings instead. In the world of Inform, build 5T18 finally made the long-awaited reform of "block structure", allowing Python-like syntax for grouped phrases, and made miscellaneous other improvements throughout. The Standard Rules were redrafted and formally advanced to version 2, and the standing I6 code used by I7 - the "template" - was completely rewritten. The first steps were made towards an official system for translating I7 into languages of play other than English, something which had previously been done but only with great difficulty. Certain run-time algorithms were optimised for speed, and all 162 open bug reports as of 26 April 2008 were closed out. Besides the new examples, new material was added to the Recipe Book to give more guidance on designing new commands (see the Commands chapter), on the looking action and on conversation. (-See Begin and end for the new way to group phrases in "if", "while" and "repeat".) (-See Next and break for ways to skip to the next iteration, or to immediately exit, a "repeat" or "while" loop.) (-See Otherwise for a new form of "if", somewhat like a "switch" statement in C or Inform 6.) (-See If for the new ability to use "unless" as a reversed form of "if".) (-See Text with variations for the new ability to use "[unless ...]" as a reversed form of "[if ...]".) (-See Moving backdrops for a new way to move backdrops to any set of rooms matching a given description.) (-See Table amendments for a way to define a new table which would amend selected rows in an existing one.) (-See Adjacent rooms and routes through the map for how to use a fast route-finding algorithm when there's memory enough to handle it.) (-See Indirect relations for similar fast route-finding through a relation.) (-See Making new substitutions for defining text substitutions which differ only in their casing, e.g., making "[Security Notice]" different from "[security notice]" - in previous releases, these were considered identical.) (-See Lists of objects for accessing the multiple object list generated when the parser acts on a command like TAKE ALL.) (-See Defining new assertion verbs for defining verbs to have meanings which are the reversal of relations, that is, have the subject and object the other way round.) (-See The built-in verbs and their meanings for the new verb "to incorporate", which expresses having something as a part: for instance, "the TV set incorporates the off button" means the same as "the off button is part of the TV set".) (-See A word about nothing for clarification of how "nothing" can be used: this build handles "nothing" much better than previous ones.) (-See Multiple endings for how to check if a scene did not end in a particular way.) (-See Printing a number of something for a new activity allowing the form of plural entries in lists, like "five gold rings", to be reworded.) (-See Printing the locale description of something for the first of three new activities which, between them, provide much finer-grained access to how room descriptions are printed.) (-See Printing the announcement of light for a new activity, used when light returns after a period of darkness.) (-See Deciding the scope of something for better control over the "place ... in scope" phrase.) (-See Understanding names for supplying additional text to be understood as referring to things in the plural.) (-See Context: understanding when for a new property, "privately-named", which enables the name of something in the source text to be kept private from the player at run-time.) (-See Printing a parser error for a new parser error, "noun did not make sense in that context".) (-See The TEST command for how to write literal apostrophes and slashes in test scripts, which previously couldn't be done.) (-See Extensions can interact with other extensions for new ways to allow an extension to vary according to which other extensions are in use at the same time, and to override parts of an included extension while keeping the rest.) (-See Authorship for more liberal extension identification: author and title can now be up to 50 characters, not up to 31; accented letters and mixed casing are now allowed; the word "and" is now allowed in extension titles; there's provision for additional credits to clarify who contributed to earlier versions, or from what an extension is converted or translated.) (-See The template layer for a description of the new system for I6 supporting code, replacing the old I6 library with something much more customisable.) (-See Translating the language of play for the beginnings of a new system for translating I7 to produce IF in languages other than English.) (-See Inform 6 objects and classes for the new unified way to force I6 translations of I7 constructions, the verb "translates into I6 as".) (-See Longer extracts of Inform 6 code for referring to properties or adjectives using the "(+" and "+)" markers.) (See example "Casino Banale") (See example "Copper River") (See example "Delicious, Delicious Rocks") (See example "Escape from the Seraglio") (See example "Formicidae") (See example "Jamaica 1688") (See example "Kiwi") (See example "The Left Hand of Autumn") (See example "Low Light") (See example "Noisemaking") (See example "Orange Cones") (See example "Priority Lab") (See example "Prolegomena") (See example "Provenance Unknown") (See example "Quiz Show") (See example "Trieste") (See example "Vouvray") (See example "WXPQ") (See example "Zorb") 26.6. What was new in build 5J39 (December 2007) (Image nov07.jpg here) As this release was being prepared, the American footballer Antonio Cromartie scored a touchdown with a continuous run of 109.88 yards, a league record unlikely ever to be broken on a pitch 110 yards long; the UK government burned two CDs with unencrypted bank details for every family with children, put them into the unregistered post, and then panicked when they never arrived; a pilot project in Fairfield, Texas, began converting carbon emissions from a power station into (edible) baking soda; there were wildfires in Malibu, floods in Tabasco and Rift Valley Fever in the Rift Valley; and a cruise liner struck an iceberg in the Antarctic and sank, but everyone was saved. In the world of Inform, build 5J39 introduced lists as first-class values. For any kind of value K, "list of K" was now also a kind of value, and rich support was provided for building and iterating over lists, dynamically resized as necessary. (-See Lists and entries for the introduction of a new chapter on lists.) (See example "Circle of Misery") (See example "Eyes, Fingers, Toes") (See example "The Fibonacci Sequence") (See example "I Didn't Come All The Way From Great Portland Street") (See example "Leopard-skin") (See example "Lugubrious Pete's Delicatessen") (See example "Robo 1") (See example "Robo 2") (See example "Sieve of Eratosthenes") (See example "What Makes You Tick") (See example "Your Mother Doesn't Work Here") 26.7. What was new in build 5G67 (November 2007) (Image oct07.jpg here) As this release was being prepared, the 50th anniversary of Sputnik 1 was marked, while Japan's Selene satellite entered lunar orbit; miraculously, all three thousand men trapped underground in an Elandsrand gold mine were rescued; Jason Lewis completed a circumnavigation by bicycle, pedal boat and kayak; the Chicago Marathon ran to a photo finish; the US conceded that it had mistakenly kidnapped a German car salesman; squirrels were declared once again safe to eat in New Jersey; and Albus Dumbledore was outed by J. K. Rowling. In the world of Inform, build 5G67 extended the range of values which can be handled to include truth states, indexed text and stored actions. Inform was made compatible with Apple's newly-released Mac OS X Leopard (10.5), including suitable QuickLook and Finder plugins for dynamic icons and cover flow showing the contents of ".inform" project bundles. Philip Chimento joined the Inform team as the author of the Gnome user interface for Linux, building on Adam Thornton's work with the underlying tools, and the first easy-to-install packages for Fedora and Ubuntu were made available. This "what's new" chapter was added to the documentation, and further work went into improving the Recipe Book with a view to making it easier to extract general solutions for general problems. All 110 open bug reports were closed: there are now once again no known issues. (-See Ordinary text and indexed text for the introduction of a new chapter on "indexed text": a new kind of value holding text which can be examined and altered character by character.) (-See Regular expression matching for an Inform implementation of the standard way to search for complicated patterns of text.) (-See Stored actions for the new "stored action" kind of value: a value which can hold any action, and can be held in variables, table entries and so on, and can be played back in later rounds.) (-See Conditions and questions for the new "truth state" kind of value, which always holds one of two values: true or false.) (-See Writing and reading tables to external files for writing and reading table columns holding text, something not possible in earlier builds.) (-See Indexed text in variables, properties and tables for the ability to specify explicitly the kind of value of a 'let' value or a table column, which are ordinarily created only implicitly - Inform deduces their kinds of value from the initial contents.) (-See Understanding things by their properties for the ability to declare synonyms for either/or properties like "open" or "closed" being used as part of the name of something understood in a command.) (-See Units for a clarification of the syntax for writing negative literal values of units, such as a weight like "-4 kg".) (-See The SHOWME command for a more detailed SHOWME than on previous builds: it now describes the current properties of what is being shown.) (See example "Actor's Studio") (See example "Alpha") (See example "Anteaters") (See example "Blackout") (See example "Bosch") (See example "Cactus Will Outlive Us All") (See example "Capital City") (See example "Celadon") (See example "The Cow Exonerated") (See example "Endurance") (See example "Fido") (See example "Fine Laid") (See example "Hymenaeus") (See example "Identity Theft") (See example "Lucy") (See example "Mr. Burns' Repast") (See example "Rocket Man") (See example "Rubies") (See example "Savannah") (See example "Situation Room") (See example "Slouching") (See example "Starry Void") (See example "Straw Into Gold") (See example "Terracottissima Maxima") (See example "What Not To Wear") (See example "Xot") 26.8. What was new in build 4X60 (23 August 2007) (Image aug07.jpg here) As this release was being prepared, Russian submersibles planted a flag on the North Pole, 4.2 km underwater; there was a crackdown on counterfeit toothpaste in Mozambique; forest fires threatened Dubrovnik, while Minnesota flooded; there was a single, unconfirmed sighting of the Yangtse River Dolphin, thought extinct since 2004; the Unix court case, SCO v. Novell, found for Novell; the quarterback of the Atlanta Falcons pled guilty to "conspiracy to sponsor a dog"; and Peter Stoychev of Bulgaria broke the speed record for swimming the English Channel. In the world of Inform, build 4X60 introduced the Recipe Book to the in-application documentation, and made a number of internal reforms, notably improving the speed of table handling at run-time. (-See Text with random alternatives for a new "[one of]...[at random]" text substitution, adopted into the core language from an earlier implementation in the extension Text Variations by Jon Ingold.) (-See Files for reading and writing external files in projects using the Glulx virtual machine: most tables can be "serialised" (i.e. stored to an external file) this way, and files can also hold general text.) (-See Defining new adjectives for the ability to name the subjects of adjective definitions, rather than having to use the sometimes grammatically clunky pronoun "it".) (-See Examples and headings in extension documentation for the new ability to supply extensions with structured, multi-part documentation rather than a single run of only a few paragraphs.) (-See Segmented substitutions for how to define multi-part text substitutions using Inform 6 code, a practice reserved for Extensions.) (-See Invocation labels, counters and storage for documentation on some of Inform's previously closed internal syntaxes for specifying complex phrases, which are now opened up for the use of Extensions.) (-See To say one of for how Extensions can contribute additional "[one of]..." constructions.) (See example "Alien Invasion Part 23") (See example "Baritone, Bass") (See example "Bic") (See example "Blink") (See example "Camp Bethel") (See example "Chanel Version 1") (See example "Do Pass Go") (See example "Flathead News Network") (See example "Further Reasons Why All Poets Are Liars") (See example "Labyrinth of Ghosts") (See example "M. Melmoth's Duel") (See example "Meet Market") (See example "Mirror, Mirror") (See example "Modern Conveniences") (See example "Saint Eligius") (See example "The Second Oldest Problem") (See example "The Unbuttoned Elevator Affair") (See example "Uncommon Ground") 26.9. What was new in build 4W37 (27 July 2007) (Image jul07.jpg here) As this release was being prepared, Chinese archaeologists remotely sensed an unknown chamber in the Tomb of the Terracotta Army; Corporal Willie Apiata became the only living New Zealander to hold the Victoria Cross, won in Afghanistan; the Ghanaian cedi became the strongest African currency; Live Earth concerts were held worldwide, and the Boeing 787 was unveiled; the US Congress passed the "Honest Leadership and Open Government Act"; prolonged dust storms swept Mars, while floods in Tewkesbury submerged the whole town save only the 12th-century Abbey. In the world of Inform, build 4W37 made miscellaneous improvements mostly centred around parsing the names of objects. A significant change not linked below, since it was an excision, was the removal of the former "player-character" kind of person: any person can now be the protagonist. (-See Understanding things by their properties for a much more general way to allow an object's current properties to be part of its name: whereas in previous builds only either/or and enumerated named properties were allowed, we can now understand properties holding numbers, times, or values of any unit.) (-See Understanding things by their relations for a new way to make object names flexible: by allowing their names to contain the names of other items to which they are related. For instance, we can Understand "box of [something related by containment]" so that BOX OF CRAYONS matches the object when and only when it contains the crayons.) (-See Articles and proper names for two new either/or properties: singular-named and proper-named. These can be used to change the grammar used with object names if an object's name alters during play, for instance if "vase" must change to "smithereens".) (-See Recorded sounds for the ability to play back music or background sounds in projects using the Glulx virtual machine.) (-See Multiple beginnings and repeats for the new concept of a "recurring scene", one which can begin over again if, after it has ended, the starting conditions are found to hold again. Previously all scenes were recurring: now scenes are by default non-recurring unless declared to be.) (-See Change of properties with values for a phrase to change map connections as if they were properties, or to change them to "nowhere".) (-See Version numbering for "authorial modesty", a new ability for Extension authors to choose to remain anonymous.) (See example "Aspect") (See example "Candy") (See example "Carnivale") (See example "Channel 1") (See example "Channel 2") (See example "Cheese-makers") (See example "Cinco") (See example "Claims Adjustment") (See example "Gopher-wood") (See example "Lanista 1") (See example "Lanista 2") (See example "Latin Lessons") (See example "Night and Day") (See example "Originals") (See example "Puff of Orange Smoke") (See example "Puncak Jaya") (See example "Rock Garden") (See example "Tilt 1") (See example "Tilt 2") (See example "Tilt 3") 26.10. What was new in build 4U65 (27 April 2007) (Image apr07.jpg here) As this release was prepared, the US Supreme Court ruled that greenhouse gases were a pollutant; the Paris-Strasbourg TGV set a new world record railway speed of 357 mph, three-quarters the cruising speed of a Boeing 737; Charles Simonyi, author of Microsoft Word, became an astronaut; the genome of the macaque monkey was published; 80,000 people attended Wrestlemania 23 at Ford Field, Detroit; and Kryptonite, Superman's fictional mineral, was unearthed in a Serbian mine. In the world of Inform, 4U65 saw a reform to the handling of actions, making it easier for actions to handle all actors equally, and the introduction of variables shared in common amongst rules which collaborate to perform a task between them. This allowed almost the entire world model of 70 built-in actions, previously hand-coded in Inform 6, to be moved into much more legible Inform 7 source text. 4U67, a Mac OS X variant, was identical except for user interface improvements. (-See Rulebook variables for assigning variables to rulebooks: these are values created when the rulebook begins, which are held in common by all of the rules within that rulebook for as long as it is being worked through, and which disappear afterwards.) (-See Activity variables for assigning variables to activities, which are similar but are held in common by all three rulebooks handling an activity: before, for and after.) (-See Action variables for assigning variables to actions, which are similar but are held in common by all of the rulebooks handling an action.) (-See Extensions in the Index for assigning a specification text to an action, used to make its Index entry more explanatory.) (-See {Actions for any actor} for a new syntax, "an actor doing something", which can be used to check if any person - player or third party - is currently doing something.) (-See Action variables for the ability to set up actions with optional matching clauses which look at action variables: for instance, tacking an optional "... onto something" clause onto the dropping action.) (See example "Croft") 26.11. What was new in build 4S08 (25 March 2007) (Image mar07.jpg here) As this release was prepared, the fence dividing Cyprus was dismantled at last - just as, for lack of such a fence, Switzerland accidentally invaded Liechtenstein; Mr Stark of California became the first Congressman in US history to declare his non-belief in God; the UK legislated for a 60% cut in carbon emissions by 2050; enigmatic lakes were imaged on Titan, and heavy snow fell in Kashmir; Martha Jones became Doctor Who's first black companion (if we don't count Frobisher the penguin); and the Bornean Clouded Leopard was declared a new species. In the immortal words of Robert Heinlein: "Bugs, Mr. Rico! Zillions of 'em! I'm a-burnin' 'em down!" Build 4S08 saw the first release of I7 for Linux, and there were useful reforms of the default value for kinds of value and of the paragraph breaking algorithm, but this was primarily a maintenance release. This release closed all 335 open bug reports, and marked the end of the experimental early days since the original Public Beta release. (-See Pattern matching for phrase declarations giving special meanings in the case of specific values being used.) (See example "Ahem") (See example "Apples") (See example "Electrified") (See example "Ferragamo Again") (See example "Hover") (See example "Lollipop Guild") (See example "Mattress King") (See example "Pages") (See example "Straw Boater") (See example "Walls and Noses") Example 1 (*): About the examples An explanation of the examples in this documentation, and the asterisks attached to them. Click the heading of the example, or the example number, to reveal the text. This is the first of about 400 numbered examples. In a few cases, such as this one, they provide a little background information, but almost all demonstrate Inform source text. The techniques demonstrated tend to be included either because they are frequently asked for, or because they show how to achieve some interesting effect. The same examples are included in both of the books of documentation, but in a different order: in Writing with Inform, they appear near the techniques used to make them work; in The Inform Recipe Book, they are grouped by the effects they provide. For instance, an example called "Do Pass Go", about the throwing of a pair of dice, appears in the "Randomness" section of Writing with Inform and also in the "Dice and Playing Cards" section of The Inform Recipe Book. Clicking the italicised WI and RB buttons at the right-hand side of an example's heading switches between its position in each book. Many computing books quote excerpts from programs, but readers have grown wary of them: they are tiresome to type in, and may only be fragments, or may not ever have been tested. The authors of Inform have tried to avoid this. All but two dozen examples contain entire source texts. A single click on the paste icon (Image paste.png here) (always placed just left of the double-quoted title) will write the complete source text into the Source panel. All that is then required is to click the Go button, and the example should translate into a working game. In most cases, typing the single command TEST ME will play through a few moves to show off the effect being demonstrated. (You may find it convenient to create a "scratch" project file for temporary trials like this, clearing all its text and starting again with each new test.) As part of the testing process which verifies a new build of Inform, each example in turn is extracted from this documentation, translated, played through, and the resulting transcript mechanically checked. So the examples may even work as claimed. But the flesh is weak, and there are bound to be glitches. We would welcome reports, so that future editions can be corrected. Each example is loosely graded by difficulty: if they were exercises in a textbook, the asterisks would indicate how many marks each question scores. As a general rule: (Image asterisk.png here) - A simple example, fairly easily guessed. (Image asterisk.png here) (Image asterisk.png here) - A complicated or surprising example. (Image asterisk.png here) (Image asterisk.png here) (Image asterisk.png here) - An example needing detailed knowledge of many aspects of the system. (Image asterisk.png here) (Image asterisk.png here) (Image asterisk.png here) (Image asterisk.png here) - A complete scenario, containing material not necessarily relevant to the topic being demonstrated. In general, the main text of Writing with Inform tries never to assume knowledge of material which has not yet appeared, but the trickier examples almost always need to break this rule. The icon at the foot of each example closes it up again. Example 2 (*): Verbosity 1 Making rooms give full descriptions each time we enter, even if we have visited before. By default, the description of a room is printed only when the player enters that room for the first time. Afterwards, the text is skipped, for brevity, though the player can see it again at any time by typing LOOK. This is not always desirable behavior, though, especially when the description of a room changes during play or we want to be sure that the player has access to all the important details: so it is also possible to supply a different default. As we saw in the previous chapter, we can set "use options" to control certain aspects of the player's experience. One of the use options is the option to Use full-length room descriptions. which changes the defaults so that the description of a room is printed every time a player enters a room, whether or not he has been there previously. "Verbosity" Use full-length room descriptions. The Wilkie Memorial Research Wing is a room. "The research wing was built onto the science building in 1967, when the college's finances were good but its aesthetic standards at a local minimum. A dull brown corridor recedes both north and south; drab olive doors open onto the laboratories of individual faculty members. The twitchy fluorescent lighting makes the whole thing flicker, as though it might wink out of existence at any moment. The Men's Restroom is immediately west of this point." The Men's Restroom is west of the Research Wing. "Well, yes, you really shouldn't be in here. But the nearest women's room is on the other side of the building, and at this hour you have the labs mostly to yourself. All the same, you try not to read any of the things scrawled over the urinals which might have been intended in confidence." Test me with "west / east". If we type "test me" during play, these commands will be carried out automatically, and we can see that when we return to the Research Wing, the description is given a second time. Some notes: the player can also turn full-length descriptions on or off with the commands "verbose" and "brief", or set a minimal-description setting with the command "superbrief". This power still belongs to the player even if we have set the use option to show full-length room descriptions by default. See the Writing with Inform chapter on use options for more discussion of these points. Moreover, we can ourselves check what the state of the descriptions is, with if set to sometimes abbreviated room descriptions: ... if set to unabbreviated room descriptions: ... if set to abbreviated room descriptions: ... Finally, it is possible to exercise more precise control over what the player sees on his first and subsequent visits to a room; see the next example for details. Example 3 (**): Slightly Wrong A room whose description changes slightly after our first visit there. A fairly common effect in interactive fiction is a room which is described differently on the first visit than on subsequent visits. We can produce this effect as follows: "Slightly Wrong" Awning is a room. "A tan awning is stretched on tent poles over the dig-site, providing a little shade to the workers here; you are at the bottom of a square twenty feet on a side, marked out with pegs and lines of string. Uncovered in the south face of this square is an awkward opening into the earth." Slightly Wrong Chamber is south of the Awning. "[if unvisited]When you first step into the room, you are bothered by the sense that something is not quite right: perhaps the lighting, perhaps the angle of the walls. [end if]A mural on the far wall depicts a woman with a staff, tipped with a pine-cone. She appears to be watching you." Test me with "look / s / look". Note the "[if unvisited]..." in the description of the Slightly Wrong Chamber. A room is considered to be "unvisited" until after the player has seen its description for the first time. The bracketed text creates a special rule for printing; we will learn more about these in the sections on text with variations and text with substitutions. Some further fine print: we might write our condition as "if unvisited", "if the location is unvisited", or "if the Chamber is unvisited" -- all of these constructions would be acceptable, but in the absence of more specifics, the condition is understood to apply to the object whose description it is. Example 4 (*): Port Royal 1 A partial implementation of Port Royal, Jamaica, set before the earthquake of 1692 demolished large portions of the city. "1691" Fort James is a room. "The enclosure of Fort James is a large, roughly hexagonal court walled with heavy stone. The walls face the entrance to Port Royal Harbour, and the battery of guns is prepared to destroy any enemy ship arriving." Unless we arrange otherwise, this will be the first room in the game because it is the first we have defined. For subsequent rooms, we do not have to say explicitly that they are rooms, as long as they are connected to a room on the map. For instance, this will automatically make Thames Street End a room: Thames Street End is south of Fort James. "The ill-named Thames Street runs from here -- at the point of the peninsula -- all the way east among houses and shops, through the Fish Market, edging by the round front of Fort Carlisle, to the point where the town stops and there is only sandy spit beyond. Lime Street, wider and healthier but not as rich, runs directly south, and to the north the road opens up into the courtyard of Fort James." Water Lane is east of Thames Street End. "Here Thames Street -- never very straight -- goes steeply southeast for a portion before continuing more directly to the east. Water Lane runs south toward Queen Street, and facing onto it is the New Prison -- which, in the way of these things, is neither. It did serve in that capacity for a time, and in a measure of the villainy which has been usual in Port Royal from its earliest days, it is nearly the largest building in the town." If we have some concern that the room name will be confused with an existing name, we can be more explicit about it using "called": East of Water Lane is a room called Thames Street at the Wherry Bridge. Thames Street at the Wherry Bridge has the description "To the southwest is the fishmarket; directly across the street is the entrance to a private alley through a brick archway." The Private Alley is south of Thames Street at the Wherry Bridge. "You're just outside the tavern the Feathers. To the north, under a pretty little archway, is the active mayhem of Thames Street, but the alley narrows down to a dead end a little distance to the south." And now we get "inside", which generates a space treated as its own area on the map. The Feathers is inside from the Private Alley. "Newly built with brick, replacing the older Feathers tavern that used to stand here. It sells wines in quantity, as well as serving them directly, and the goods are always of the best quality. There's a room upstairs for those wanting to stay the night." The Feathers Bedroom is above the Feathers. And if we like we can declare a number of rooms for which we will come back and write the descriptions later. There is no obligation for the description to occur at the first definition of the room. Lime Street is south of Thames Street End. For efficiency, we can also write multiple sets of connections at once: Queen Street East is east of Queen Street Middle and south of Private Alley. Clicking Go will translate this description into a sketchy but working simulation of Port Royal, in which we can type movement commands like EAST or SOUTH to explore the streets. Looking at the World tab of the Index, we can also see a schematic map of the simulation as it currently stands. Like the rest of the Index, this is provided entirely for the author's benefit, and is not visible to the player. (Though if we do decide that we want players to have access to a printed map while they play, Inform can help: we will return to the layout of Port Royal in the chapter on Publishing.) The following Test command allows us to type TEST ME and explore the map we just devised: Test me with "s / e / e / e / e". Example 5 (**): Up and Up Adding a short message as the player approaches a room, before the room description itself appears. Sometimes when a player moves from one room to another, we want to imply that a considerable amount of time elapses, or that something interesting occurs on the way. In that case, we might want to print more than just the room description itself. Here is how we might define a couple of rooms that are far apart: "Up and Up" The Plain of the Skull is below the Endless Tower. The description of the Plain of the Skull is "A vast and trackless plain, enlivened only by the bones of those who have previously tried and failed to cross. Above you is the Endless Tower, which rises half-way to the moon." The description of the Endless Tower is "From up here the Plain of the Skull seems only a small bald patch: the world is round and most of it is covered with trees. Far off to the southwest is a shimmering surface that might be water; but there are no signs of cities or civilizations, only the lizard-skeletons." And now we borrow from the instructions on Actions to create our actual message. "Before..." introduces a rule that occurs when the player tries to do something; in this case, we will make a Before rule for going to the tower. Before going to the Endless Tower: say "You climb... and climb... and climb... The sun sets. The moon rises. The wind begins to blow. You continue to climb..." The player carries a bit of harness. The description of the harness is "A strip of worked leather and a loop of metal, scavenged from one of the skeletons on the plain. Without it, you might think your entire quest was in vain." Test me with "look / up". Example 6 (***): Starry Void Creating a booth that can be seen from the outside, opened and closed, and entered as a separate room. Sometimes we may want a room to be visible from the outside in one location, but treated as a separate location when we are inside. The simplest way to do this is to make the exterior form of the object into a door object, and to describe it differently from different vantage points. (Doors in general are described more fully in the Doors section of the Things chapter.) "Starry Void" The Center Ring is a room. The magician's booth is a door. "[if the player is in Center Ring]A magician's booth stands in the corner, painted dark blue with glittering gold stars.[otherwise if the magician's booth is closed]A crack of light indicates the way back out to the center ring.[otherwise]The door stands open to the outside.[end if]". Here we've arranged for the booth to be described in the initial room description in different ways depending on where the player is when viewing it. We might like to do the same if the player takes a closer look: Instead of examining the magician's booth in the Center Ring: say "It is dark blue and glittering with gold stars. [if the booth is open]The door currently stands open[otherwise]It has been firmly shut[end if]." Instead of examining the magician's booth in the Starry Void: say "The booth door is [if the magician's booth is open]wide open[otherwise]shut, admitting only a thin crack of light[end if]." And now we put it in place: The magician's booth is inside from Center Ring and outside from Starry Void. ...and make sure that the booth-and-door object responds to all the names we have used for it in different places: Understand "door" or "of" or "the" or "light" or "crack" or "thin crack" as the booth. Test me with "examine booth / open door of the booth / in / examine door / close door / look / examine crack of light". A final nice touch, if we're so inclined, is to borrow from the Basic Actions chapter and make the player automatically open the booth door before trying to enter: Before going through the closed magician's booth: say "(first opening the door of the booth)[command clarification break]"; silently try opening the booth. For the contrasting case of a space that is nested inside another place and is not its own room -- say a stall at an open-air market, or a rowboat on a lake -- see the example "Tamed". Example 7 (*): Port Royal 2 Another part of Port Royal, with less typical map connections. "1691" Thames Street End is a room. If we check out a map of historic Port Royal, we find that Thames Street End bends around the northwest tip of the peninsula and becomes the (very) roughly north/south Fisher's Row. We can't put Fisher's Row south of Thames Street End, though, because Lime Street is already going that way. So instead, let's have a map connection that bends around from west to north: West of Thames Street End is north of Fisher's Row. Now continuing west along Thames Street, or north along Fisher's Row, will bring us around the corner in question. Asymmetric map connections should be used carefully. They're good for representing the layout of the real world, which tends not to be laid out on a convenient square matrix, but if exits are not described clearly they can be disorienting for the player. So let's be sure to make things clear: The description of Fisher's Row is "A waterfront street that runs south towards Chocolata Hole, where the small craft are harboured. It also continues north around the tip of the peninsula from here, turning into the east-west Thames Street." Meanwhile, suppose Fort James is in a prominent position, raised a bit from its surroundings; maybe the player should be able to go down from there, as well as south, to get to Thames Street End. Thames Street End is down from Fort James. Thames Street End is south from Fort James. But we don't want the upward direction to work: Up from Thames Street End is nowhere. Test me with "n / d / u / w / e / n / s". Example 8 (*): The Unbuttoned Elevator Affair A simple elevator connecting two floors which is operated simply by walking in and out, and has no buttons or fancy doors. This is very simple. The interior of the elevator is a single room, but which is mapped east of both of its termini. The reverse map connection, west from the elevator, can only go to a single room, and that's what determines which floor the elevator is on. "The Unbuttoned Elevator Affair" UNCLE Headquarters is a room. "The steel nerve-center of the free world's battle against the Technological Hierarchy for the Removal of Undesirables and the Subjugation of Humanity. Being against technology, we have only a very simple elevator to the east." Del Floria's Tailor Shop is a room. "Only trained anti-THRUSH agents recognise the booth in the east wall as a secret elevator." The Secret Elevator is east of UNCLE Headquarters. The Secret Elevator is east of Del Floria's Tailor Shop. After going to the Secret Elevator: say "The doors automatically close, there is a rush of motion, and they open again."; if UNCLE Headquarters is mapped west of the Secret Elevator, now Del Floria's Tailor Shop is mapped west of the Secret Elevator; otherwise now UNCLE Headquarters is mapped west of the Secret Elevator; continue the action. Test me with "east / west / east / west". Example 9 (*): Port Royal 3 Division of Port Royal into regions. "1691" We should go ahead and do all our room definitions first... Fort James is a room. "The enclosure of Fort James is a large, roughly hexagonal court walled with heavy stone. The walls face the entrance to Port Royal Harbour, and the battery of guns is prepared to destroy any enemy ship arriving." Thames Street End is south of Fort James. "The ill-named Thames Street runs from here -- at the point of the peninsula -- all the way east among houses and shops, through the Fish Market, edging by the round front of Fort Carlisle, to the point where the town stops and there is only sandy spit beyond. Most of that stretch is full of people at all hours. Imported goods are moved off of ships and taken to distributors; exported goods are brought to be loaded; and there is one public house and brothel for every ten inhabitants. Lime Street, wider and healthier but not as rich, runs directly south, and to the north the road opens up into the courtyard of Fort James." Lime Street is south of Thames Street End. West of Thames Street End is north of Fisher's Row. The description of Fisher's Row is "A waterfront street that runs south towards Chocolata Hole, where the small craft are harboured. It also continues north around the tip of the peninsula from here, turning into the east-west Thames Street." Thames Street End is down from Fort James. Up from Thames Street End is nowhere. Water Lane is east of Thames Street End. "Here Thames Street -- never very straight -- goes steeply southeast for a portion before continuing more directly to the east. Water Lane runs south toward Queen Street, and facing onto it is the New Prison -- which, in the way of these things, is neither. It did serve in that capacity for a time, and in a measure of the villainy which has been usual in Port Royal from its earliest days, it is nearly the largest building in the town." East of Water Lane is a room called Thames Street at the Wherry Bridge. Thames Street at the Wherry Bridge has the description "To the southwest is the fishmarket; directly across the street is the entrance to a private alley through a brick archway." The Fishmarket is southwest of Thames Street at the Wherry Bridge. The Private Alley is south of Thames Street at the Wherry Bridge. "You're just outside the tavern the Feathers. To the north, under a pretty little archway, is the active mayhem of Thames Street, but the alley narrows down to a dead end a little distance to the south." The Feathers is inside from the Private Alley. "Newly built with brick, replacing the older Feathers tavern that used to stand here. It sells wines in quantity, as well as serving them directly, and the goods are always of the best quality. There's a room upstairs for those wanting to stay the night." The Feathers Bedroom is above the Feathers. Thames Street by the King's House is east of Thames Street at the Wherry Bridge. "The King's House is reserved for the use of the Governor, but he does not live in it, and it is frequently being rented out to some merchant so that the government will at least derive some value from it. It is nearly the least interesting establishment on Thames Street, and the crowd -- which, to the west, is extremely dense -- here thins out a bit." Thames Street before Fort Carlisle is east of Thames Street by the King's House. "Here Thames Street, formerly a respectable width, narrows to a footpath in order to edge around the front of Fort Carlisle, underneath the mouths of the cannon. There are no buildings on the harbour side of Thames Street at this point, which means that you have an unusually good view of the ships at dock, water beyond, and the Blue Mountains rising on the other side of the harbour." South of Thames Street before Fort Carlisle is a room called Fort Carlisle. The description of Fort Carlisle is "Handsomely arrayed with cannons which you could fire at any moment -- though of course there are ships at dock which might be in the way." Queen Street End is south of Lime Street. Queen Street Middle is east of Queen Street End. Queen Street East is east of Queen Street Middle and south of Private Alley. Queen Street at the Prison is east of Queen Street East. Now, if we like, we can create regions to distinguish the coast from the portions of town that aren't on the water: Inland is a region. Queen Street End, Queen Street Middle, Queen Street East, Private Alley, Lime Street, and Queen Street at the Prison are in Inland. Waterfront is a region. Thames Street before Fort Carlisle, Thames Street by the King's House, Thames Street at the Wherry Bridge, Water Lane, Fishmarket, Fisher's Row, and Thames Street End are in Waterfront. There's no rule that regions must be contiguous, so we could if we like make a region consisting just of the two forts: Military Holdings is a region. Fort Carlisle and Fort James are in Military Holdings. And we might make the Feathers Tavern part of the Inland area, but within its own subcategory: Tavern is a region. It is in Inland. Feathers and Feathers Bedroom are in Tavern. Now the index map will be colored to reflect our regions, and later in the game development we would be able to make rules that affect just one region at a time. Example 10 (*): First Name Basis Allowing the player to use different synonyms to refer to something. Sometimes we create objects that we want the player to be able to call by different names: a television that should also answer to "tv" and "telly", for instance, or a refrigerator the player might also call "fridge". In this case, we can use instructions like Understand "tv" and "telly" as the television. to add extra names to the object we've defined. "First Name Basis" The Crew Lounge is a room. "Deliberately spartan: the crew feels weight restrictions here first, so there aren't any chairs, just a few thin pads on the ground." The holographic projector is a device in the Crew Lounge. "The one major source of entertainment is the holographic projector, a top of the line Misthon 9000, on which you view every beam you can get." Understand "holo" or "holograph" or "Misthon" or "9000" as the projector. The description of the projector is "[if switched on]The projector is now playing a documentary about the early politics of the Mars colony.[otherwise]The air above the projector is disappointingly clear.[end if]". (This description is for local color; we will learn more about devices, and conditions like "if switched on", later in this chapter.) By default, Inform does not understand the names of an object's kind as referring to that object, unless the object has no other name of its own. We can change this, if we like, by defining names that should be applied to everything of a given kind: Lewis and Harper are men in the Crew Lounge. Understand "man" or "guy" or "chap" or "lad" or "male" as a man. Understand "men" or "chaps" or "lads" or "guys" or "males" as the plural of a man. The description of Lewis is "A wiry, excitable engineer who just signed aboard last week." The description of Harper is "Harper's a good guy: taciturn when sober, affectionate when drunk, but rarely annoying in either state." Test me with "x holo / x man / lewis / x guy / harper / turn on projector / x holo projector / get men". Inform's naming abilities go considerably further, in fact: we can also instruct it to understand words only under certain circumstances, or only when they appear with other words. Fuller details may be found in the chapter on Understanding. Example 11 (*): Midsummer Day A few sentences laying out a garden together with some things which might be found in it. "Midsummer Day" East of the Garden is the Gazebo. Above is the Treehouse. A billiards table is in the Gazebo. On it is a trophy cup. A starting pistol is in the cup. In the Treehouse is a container called a cardboard box. Test me with "up / x box / d / e / x table / x cup / x pistol / get cup". Example 12 (*): Tamed Examples of a container and a supporter that can be entered, as well as nested rooms. Within a room, we might have containers and supporters that a player can enter. A chair, stool, table, dais, or pedestal would be an enterable supporter (anything we would describe a person as being "on"); a cage, hammock, or booth would be an enterable container (because we would describe the person as being "inside"). When the player is in or on something, he is able to see the rest of the contents of the room, but a note such as "(in the hammock)" or "(on the poster bed)" is added to the room title when he looks around. Here is an example to show off the possibilities: "Tamed" The Center Ring is a room. The cage is in the Center Ring. A lion is an animal in the cage. The cage is enterable, openable, transparent, and closed. Notice that we made the cage transparent. Strictly speaking it is not made of transparent materials, but we can see into (or out of) a closed cage due to the gaps between the bars, so that from Inform's point of view a cage behaves much like a large sturdy glass box. (If we really wanted to make a distinction between, say, an airtight container and one with perforations, we could do so, but Inform does not model such nuances by default.) If a container is not transparent, we can see into and out of it only when it is open. Supporters are a bit more straightforward because there is no circumstance in which they separate the player from the rest of the world: The pedestal is in the Center Ring. It is enterable. And in fact we can tell Inform that the player starts on the pedestal with this line: The player is on a pedestal. Now the player will begin there rather than just in the Center Ring. This last bit is an entirely unnecessary bit of local color, but if we're going to keep getting into and out of the lion's cage, we ought to expect him to take notice: Every turn when the player is in the cage: if a random chance of 1 in 2 succeeds, say "The lion eyes you with obvious discontent."; otherwise say "Though the lion does not move, you are aware that it is watching you closely." Randomness is explained more completely in the chapter on Change, and every turn rules in the chapter on Time. Finally, we might want a container whose interior is modeled as its own separate room: say, a magician's booth in which volunteers are made to disappear. The magician's booth is a container in Center Ring. "Off to one side is a magician's booth, used in disappearing acts. The exterior is covered with painted gilt stars." The booth is enterable, open, not openable, and fixed in place. Now we create our other location: Inside from the Center Ring is the Starry Vastness. ...which handles the case of the player typing >IN. (We will not assume by default that he wants to get into the cage with the lion, this being obviously perilous.) But we also want to make sure that the player who types >ENTER BOOTH winds up in the same place, so we should add: Instead of entering the magician's booth: try going inside. Test me with "get in cage / open cage / get in cage / z / close cage / out / open cage / get on pedestal / get off / look / enter booth / out". Example 13 (*): Disenchantment Bay 1 A running example in this chapter, Disenchantment Bay, involves chartering a boat. This is the first step: creating the cabin. To begin with the title: "Disenchantment Bay" There are many Disenchantment Bays across the world, named by eighteenth-century ships' captains - one in Antarctica, another in Tasmania, for instance. The most famous is probably the one where Lewis and Clark's expedition broke through to the Pacific. But ours is the one in Alaska, named in 1791 by a Spanish navigator who had hoped it might lead to the fabled Northwest Passage, and all of this history is beside the point since the game is set in the present day. The Cabin is a room. "The front of the small cabin is entirely occupied with navigational instruments, a radar display, and radios for calling back to shore. Along each side runs a bench with faded blue vinyl cushions, which can be lifted to reveal the storage space underneath. A glass case against the wall contains several fishing rods. Scratched windows offer a view of the surrounding bay, and there is a door south to the deck. A sign taped to one wall announces the menu of tours offered by the Yakutat Charter Boat Company." We might want to start with the glass case. The Cabin contains a glass case. In the glass case is a collection of fishing rods. Now Inform will have guessed that the case is a container, but its default idea of a container is something like a bucket: permanently open and not able to be opened and shut. We can change that: The case is closed, transparent, and openable. We get a similar set of guesses if we write The bench is in the cabin. On the bench are some blue vinyl cushions. Using "some" rather than "a" or "the" tells Inform that the cushions are to be referred to as a plural object in the future. And because of the "on the bench..." phrase, Inform will guess that the bench is a supporter and that it is fixed in place and cannot be moved from room to room. We do have to tell it that the bench can be sat on, though: The bench is enterable. And now a short script, so that if we type TEST ME, we experiment with the case and bench: Test me with "examine case / get rods / open case / get rods / sit on bench / take cushions / get up" Example 14 (*): Replanting Changing the response when the player tries to take something that is scenery. By default, "TAKE OAK" in the example above will produce the response "That's hardly portable." This is fine under many circumstances, but also a bit generic, so we might want to override it for a specific game. "Replanting" The Orchard is a room. "Within this quadrille of pear trees, a single gnarled old oak remains as a memory of centuries past." The gnarled old oak tree is scenery in the Orchard. Instead of taking some scenery: say "You lack the hulk-like strength." Test me with "take oak". Here we've used an "instead" rule; we will learn more about these in the section on actions. This allows us to define our own results for taking an object. Note: "scenery" is a property of an object (about which we will hear more later). So when we use it in rules, we can talk about "some scenery", "something that is scenery", or even "a scenery thing" -- the last one doesn't sound much like English, but is a more plausible construction with other adjectives. Example 15 (*): Disenchantment Bay 2 Disenchantment Bay: creating some of the objects in the cabin's description. If we compile our last version of the cabin, we get a room where the glass case and the bench are listed separately from the room description, even though they have already been mentioned once. We can prevent this by making the already-mentioned things scenery: "Disenchantment Bay" The Cabin is a room. "The front of the small cabin is entirely occupied with navigational instruments, a radar display, and radios for calling back to shore. Along each side runs a bench with faded blue vinyl cushions, which can be lifted to reveal the storage space underneath. A glass case against the wall contains several fishing rods. Scratched windows offer a view of the surrounding bay, and there is a door south to the deck. A sign taped to one wall announces the menu of tours offered by the Yakutat Charter Boat Company." The Cabin contains a glass case. In the glass case is a collection of fishing rods. The case is closed, transparent, and openable. The case is scenery. The bench is in the cabin. On the bench are some blue vinyl cushions. The bench is enterable and scenery. The cushions are scenery. Generally speaking, it is a good idea to recognize the player's attempts to interact with any objects mentioned in the room description, so we should also provide Some navigational instruments, some scratched windows, a sign, a radar display, and some radios are scenery in the cabin. Test me with "examine instruments / x windows / x sign / x display / x radios". The door and the view will need to be done as well, but they are special cases which we will get to shortly. As noted, making something scenery also means that the player will be prevented from picking it up and carrying it away. This is sensible, though: if an object can be removed from the room where it first appears, we should be careful about mentioning it in the main room description; otherwise, it will continue to be described as present even when someone has carried it off. Example 16 (*): Disenchantment Bay 3 Disenchantment Bay: adding a view of the glacier. Suppose we wanted to have the glacier visible from the Cabin of our boat, and anywhere else we might add to the game: The view of the Malaspina glacier is a backdrop. It is everywhere. The description is "The Malaspina glacier covers much of the nearby slope, and -- beyond it -- an area as large as Rhode Island." Example 17 (*): Disenchantment Bay 4 Disenchantment Bay: fleshing out the descriptions of things on the boat. Currently we have provided objects for most of what is on the boat, but it's not very interesting to look at. We might want to give some more description to these things. "Disenchantment Bay" The Cabin is a room. "The front of the small cabin is entirely occupied with navigational instruments, a radar display, and radios for calling back to shore. Along each side runs a bench with faded blue vinyl cushions, which can be lifted to reveal the storage space underneath. A glass case against the wall contains several fishing rods. Scratched windows offer a view of the surrounding bay, and there is a door south to the deck. A sign taped to one wall announces the menu of tours offered by the Yakutat Charter Boat Company." The Cabin contains a glass case. In the glass case is a collection of fishing rods. The case is closed, transparent, and openable. The case is scenery. The bench is in the cabin. On the bench are some blue vinyl cushions. The bench is enterable and scenery. The cushions are scenery. Some navigational instruments, some scratched windows, a radar display, and some radios are scenery in the cabin. The description of the instruments is "Knowing what they do is the Captain's job." The description of the windows is "They're a bit the worse for wear, but you can still get an impressive view of the glacier through them. There were whales earlier, but they're gone now." The description of the radar is "Apparently necessary to avoid the larger icebergs." The description of the radios is "With any luck you will not need to radio for help, but it is reassuring that these things are here." The order in which we define these things is fairly open. We could also define an object so: A sign is scenery in the Cabin. The description is "You can get half-day and full-day sight-seeing tours, and half-day and full-day fishing trips." Where "the description" is assumed to refer to the thing most recently defined, if no object is specified. The view of the Malaspina glacier is a backdrop. It is everywhere. The description is "The Malaspina glacier covers much of the nearby slope, and -- beyond it -- an area as large as Rhode Island." Test me with "examine sign / examine glacier / examine instruments / examine windows / examine radar / examine radios / take the cushions / take the glacier". These last two commands show how scenery and backdrops are automatically impossible for the player to take. Example 18 (**): Laura Some general advice about creating objects with unusual or awkward names, and a discussion of the use of printed names. Occasionally it is useful to give something a printed name because we want to call it something extremely long-winded; give one thing a name that is the subset of the name of something else; or use words such as "with" or "and" that are likely to confuse Inform into thinking that the object name ends before it actually does. Often it is enough to preface these ambiguously-titled things with "a thing called..." or "a supporter called..." or the like, as here: South of Spring Rolls is a room called Hot and Sour Soup. prevents Inform from trying to read "Hot and Sour Soup" as two separate rooms, while The player carries an orange ticket. The player carries a thing called an orange. creates two objects instead of the one orange ticket that would result if the second sentence were merely "The player carries an orange." Even so, if we try to compile The player carries a thing called an incriminating photograph of a woman with blonde hair. Inform will misunderstand our meaning. So we might instead give the photograph a printed name: "Laura" The City of Angels is a room. The incriminating photograph is carried by the player. The printed name of the incriminating photograph is "incriminating photograph of a woman with blonde hair". Now we've gotten around any awkwardness with printing the name -- but we also need to understand when the player refers to the photograph. When we define the names of objects under normal circumstances, Inform takes care of this automatically, but if we have especially set the printed name, we must also specially define the appropriate terms for the player to use. For this we need "understand", which will be explained in much more depth in a later chapter: Understand "woman" or "with" or "blonde" or "hair" or "of" or "a" as the incriminating photograph. Test one with "x photograph / x incriminating photograph of a woman with blonde hair / x hair / x blonde / x woman with blonde hair / x incriminating photograph of a woman". That's probably as far as we really need to go, and if you are satisfied with this behavior, there is no need to read on. One possible objection to this solution is that Inform will accept some nonsensical formulations as applying to the photograph: for instance, it will allow >EXAMINE PHOTOGRAPH OF, >X BLONDE PHOTOGRAPH WOMAN INCRIMINATING, or even >X OF ...though in the case there were two items with "of" names, the game would disambiguate with a question such as "Which do you mean, the incriminating photograph of a woman with blonde hair or the essence of wormwood?" Traditionally, Inform has tended to be fairly flexible about word order, preferring to err in the direction of leniency. On the other hand, there are times when we need more exacting rules in order to distinguish otherwise similar cases. Two features allow us to specify more exactly if we so desire. The first is that, if we specify a whole phrase as the name of something, all the words in that phrase are required, in the order given. Thus "Understand "blonde hair" as the photograph" would require that both "blonde" and "hair" be present, and would not recognize >X BLONDE, >X HAIR BLONDE, or >X HAIR. Second, we can create tokens, such as "Understand "blonde hair" or "hair" as "[hair]", and then use these tokens in match phrases. This saves a good deal of time when we want to specify a number of different but fussy alternatives. So, for instance, here is a drawing that would not respond to >X OF, or >X BROWN EYES, but would respond to >X DRAWING OF MAN WITH BROWN EYES, >X MAN WITH BROWN EYES, and so on: The drawing is carried by the player. The printed name of the drawing is "drawing of a man with brown eyes". Understand "eyes" or "brown eyes" as "[brown eyes]". Understand "man" or "man with [brown eyes]" or "brown-eyed man" as "[man]". Understand "[man]" or "drawing of [man]" or "drawing of a [man]" as the drawing. Test me with "test one / test two". Test two with "x drawing / x man / x of / x drawing of man / x drawing of a man / x drawing of a man with brown eyes / x drawing of a brown-eyed man / x brown eyes". Further refinements are possible: the "privately-named" attribute tells Inform not to try to understand the source name of an object at all, so if we write The purple rabbit is a privately-named thing. ...the player will not be able to refer to it as "purple" or "rabbit" or "purple rabbit". There are also ways to make names to refer to entire kinds of objects (so "dude" will refer to any man in the game); to specify names that only refer to objects in the plural (so GET PICTURES will pick up several pictures together); to reflect an object's properties (so "red apple" works only as long as the apple is in fact red); or even to refer to the object's relationships to other objects (so "bottle of wine" works only when wine is indeed in the bottle). All these refinements are discussed in the chapter on Understanding. Example 19 (*): Disenchantment Bay 5 Disenchantment Bay: adding the door and the deck to our charter boat. We mentioned that there is a door out to the deck in our example. The following two sentences will create both the door and the other room: The cabin door is south of the Cabin and north of the Deck. It is a door and scenery. Now Inform has constructed a generic room called "Deck" to the south. It has neither a description nor any contents yet, but we could fix that in time. It does have a view of the glacier, though, since we defined the glacier view to be everywhere. Example 20 (**): Escape Window that can be climbed through or looked through. Suppose we want to offer the player a window he can climb through, instead of a boring ordinary door. Our window will be like a door in that it connects two rooms, appears in both places, and impedes movement when it is shut. But we also want to add that we can look through it and see what lies on the other side; and we further want to understand "climb through window" or "jump through window" as attempts to pass through it. We'll start by defining a couple of rooms and making the window a door between them. "Escape" Your Bedroom is a room. The bedroom window is a door. It is west of Your Bedroom and east of the Grassy Slope. Now we have a "bedroom window" object which can be entered. Now, to catch the case where the player types "LOOK THROUGH WINDOW": Instead of searching the window: say "Through the window, you make out [the other side of the window]." The other side of a door is always defined to be the room that we are not currently in when doing the check. When we are in the bedrooom, the other side will be the grassy slope, and vice versa. "Searching" is the action that occurs when the player attempts to LOOK THROUGH something. (To review what grammar gives rise to what actions, we can always consult the Actions portion of the Index.) Next we want to cover the case where we climb through the window: Instead of climbing the window: try entering the window. And because "climb window" is understood but "climb THROUGH window" is not, we will have to borrow from the chapter on Understanding to add some new vocabulary to the game (and we'll add Jump too, while we're at it): Understand "climb through [something]" as climbing. Understand "jump through [something]" as climbing. Now the final piece: Inform will already keep the player from going through a closed window, but it will say "You can't, since the bedroom window is in the way." This is probably not ideal, so we can replace the instruction thus: Instead of going through the closed window: say "The window is shut: you'd break the glass." Test me with "look through window / climb through window / open window / climb through window / look through window / close window / e / open window / e". Example 21 (***): Garibaldi 1 Providing a security readout device by which the player can check on the status of all doors in the game. Suppose we would like to allow the player to view the status of all the doors functioning in the game; and we want to identify those doors by mentioning which two rooms they connect. The following uses some techniques that will be covered in later chapters, but the basic idea may be obvious: "Garibaldi" The security readout is a device. The description of the readout is "The screen is blank." Instead of examining the switched on security readout: say "The screen reads: [fixed letter spacing]"; say line break; repeat with item running through doors: say line break; say " [item] ([front side of the item]/[back side of the item]): [if the item is locked]LOCKED[otherwise]UNLOCKED[end if]"; say variable letter spacing; say paragraph break. It is more or less arbitrary which room winds up as the "front side" and which as the "back", but in this case it hardly matters. The player carries the security readout. The Docking Bay is a room. The inner airlock is a door. It is north of the Docking Bay and south of the Zocalo. The inner airlock is lockable and unlocked. The outer airlock is lockable and locked. It is a door. It is south of the Docking Bay and north of Space. The quarantine seal is a door. It is west of the Zocalo and east of Medlab. Quarantine seal is locked. The security pass unlocks the inner airlock. The player carries the security pass. Test me with "x readout / turn on readout / x readout / lock inner airlock with security pass / x readout". Example 22 (*): Disenchantment Bay 6 Disenchantment Bay: locking up the charter boat's fishing rods. It stands to reason that the captain wouldn't let just anyone meddle with his fishing equipment; maybe he keeps that case locked. We could replace the case description with this one, instead: The Cabin contains a glass case. In the glass case is a collection of fishing rods. The case is closed, transparent, openable, lockable, and locked. The case is scenery. The small silver key unlocks the case. Now there's a silver key that will unlock it -- though since we haven't said where the key is, the player will never be able to find it in the game. (If we look at the World index, we find "small silver key" right at the bottom, not inside any of the rooms. That is as good as not existing at all -- though we usually use the term "out of play" -- but as we will later see, it is possible to have things initially out of play but brought into existence later on.) Example 23 (**): Neighborhood Watch A locked door that can be locked or unlocked without a key from one side, but not from the other. Suppose we want a locked door that can be opened with a key, but is also openable by hand without a key from one side only. We start by defining an ordinary lockable door and the key that controls it: "Neighborhood Watch" The shabby door is a door. It is outside from the Studio Apartment and inside from the Rickety Stairwell. The shabby door is locked. The brass key is carried by the player. It unlocks the shabby door. The next part is going to require that we modify the normal operation of the "lock" command. "Lock" ordinarily requires that the player supply two objects: a thing he wants to unlock, and the key he wants to use on it. The full command is LOCK DOOR WITH THE KEY, and Inform will not accept simply LOCK DOOR as locking. Therefore, we're going to need to create our own new variant on the lock verb (and the unlock verb, while we're at it). The full procedure for this is laid out in the chapters on Action and Understanding, but here is an example: Understand "lock [something]" as locking keylessly. Locking keylessly is an action applying to one thing. Here we've created a new action -- locking something without a key -- and we've told Inform to understand LOCK DOOR as this action, rather than an incomplete command to LOCK DOOR WITH SOMETHING. Now we add some instructions so that the game will not let us use this keyless unlocking command unless we're in the right place or are properly equipped: Check locking keylessly: if the noun is not a door, say "[The noun] is not something you can lock." instead; if the noun is locked, say "[The noun] is already locked." instead; if the player carries the brass key and the player is in the Stairwell, try locking the noun with the brass key instead; if the player is in the Stairwell, say "You can't lock the door from this side without the key." instead. This check rule is performed before the keyless locking action succeeds. The first thing we do is try to use the key if the player is outside and has the key: this way, LOCK DOOR will turn automatically into LOCK DOOR WITH THE KEY, under circumstances where that is both possible and necessary. The second thing is to check whether the player is outside but keyless, and, if so stop the action from being performed successfully. Here we print a failure message followed by the word "instead", which tells Inform that we've substituted some other outcome for the usual performance of the action. Now we're reasonably sure that the player is only locking keylessly in the case that he is inside the Studio. (We might have to do a more thorough check for this if there were more than two rooms, but as it is, the player can only be in the Stairwell or in the Studio, so if we have ruled out the Stairwell, we are safe.) So now we want to add what happens when locking-without-a-key command succeeds: Carry out locking keylessly: now the noun is locked. That's it. We've just told Inform to make the door be locked. "Now..." syntax will be explained more thoroughly in the chapter on change. But we still haven't described to the player what just happened, so let's provide a description of that, too: Report locking keylessly: say "You flip over the deadbolt to lock [the noun]." And now we have to do a similar set of things for unlocking: Understand "unlock [something]" as unlocking keylessly. Unlocking keylessly is an action applying to one thing. Check unlocking keylessly: if the noun is not a door, say "[The noun] is not something you can lock." instead; if the noun is unlocked, say "[The noun] is already unlocked." instead; if the player carries the brass key and the player is in the Stairwell, try unlocking the noun with the brass key instead; if the player is in the Stairwell, say "You can't unlock the door from this side without the key." instead. Carry out unlocking keylessly: now the noun is unlocked. Report unlocking keylessly: say "You flip over the deadbolt to unlock [the noun]." Test me with "unlock door / drop key / open door / out / close door / lock door / open door / in / get key / out / close door / lock door / unlock door". Some (but not all) of this work is done for you if you like by the Locksmith extension. If you prefer, you can include that extension, then follow the documentation in order to implement the remainder of the scenario. Locksmith takes care of implementing the additional locking and unlocking actions, and provides some other conveniences. Example 24 (*): Disenchantment Bay 7 Disenchantment Bay: making the radar and instruments switch on and off. If we would like the player to be able to turn instrumentation on and off, we could add a line to this effect: The radar, the instruments, and the radios are devices. And since the captain is probably not navigating blind, we might also want to say The radar and the instruments are switched on. Example 25 (**): Down Below A light switch which makes the room it is in dark or light. Suppose we want to have a room with a light switch. Turning the switch off makes the room go dark; turning it on restores the light. This kind of switch is an obvious candidate as a device. "Down Below" Terrifying Basement is a room. The light switch is a switched on device in the Terrifying Basement. It is fixed in place. Here we define our light switch, and we also make it start out as "switched on". The Terrifying Basement will also start out lit (as all rooms do, by default, unless we specifically say that they are dark). We further say that it is fixed in place to avoid the ludicrous possibility of the player picking it up and carrying it away. Next we add some instructions to control how turning the light switch on and off affects the room light. These borrow from later chapters on actions, but the gist may be obvious anyway: Carry out switching off the light switch: now the Terrifying Basement is dark. Carry out switching on the light switch: now the Terrifying Basement is lighted. Inform already has the idea of light and darkness built in; we will see more about this later, and the Phrasebook (in the Index tab) also contains a list of all the adjectives (lighted, dark, etc) which are important to use here. Speaking of the Index, the Actions tab contains a list of all the grammar that can be used to activate a given command: for instance, the switching action responds to "switch [something]" or "turn on [something]". In this case, we may want to give the player an extra option or two. It would be pretty natural for a player to try >FLIP SWITCH, so let's add that in: Understand "flip [something switched off]" as switching on. Understand "flip [something switched on]" as switching off. Understand "flip [something]" as switching on. The nuances of this will be explored in the chapter on Understanding. What is useful to know here is that we have taught Inform to understand that >FLIP LIGHT SWITCH means to turn it on when the switch is already off; if the switch is already on, FLIP SWITCH means to turn the switch off. Depending on the kind of device we are modeling (button? lever? dial?), we might want to write similar lines for commands such as PUSH, PRESS, PULL, TURN, and so on. Finally, we need to deal with a special case. In general, the player cannot interact with other things in a dark room because he can't see them, but if we adhered strictly to this it would be impossible for him to find the light switch to turn it back on. So we need something from the chapter on Activities to change this: After deciding the scope of the player when the location is the Terrifying Basement: place the light switch in scope. Upstairs is above the Terrifying Basement. Test me with "turn off light / look / flip light switch". Example 26 (*): Peugeot A journey from one room to another that requires the player to be on a vehicle. Let's say that our protagonist is about to flee . Obviously, he can't make the journey on foot; he needs transportation. "Peugeot" Include Rideable Vehicles by Graham Nelson. The Lot is a room. The ten-speed bike is a rideable vehicle in the Lot. We make the ten-speed bike a rideable vehicle because we want to say that the player is on it rather than in it. Then our other room: Cambridge is east of the Lot. And now we borrow from the Actions chapter to prevent travel without the proper equipment: Instead of going to Cambridge when the player is not on the ten-speed bike: say "It's a long journey to Cambridge: you'll never make it on foot." After going to Cambridge: say "You begin pedalling determinedly."; continue the action. Test me with "e / get on ten-speed bike / e". Example 27 (**): Disenchantment Bay 8 Disenchantment Bay: a pushable chest of ice for the boat. We probably do not need a vehicle to ride around our boat, but there might be a heavy ice chest that can only be pushed from room to room: The ice chest is a closed openable container in the Deck. "A very heavy ice chest sits on the ground." It is fixed in place and pushable between rooms. A quantity of ice is in the chest. The description is "Ready and waiting just in case there's any fish needing to be kept cool." This anticipates a later chapter, but it would probably be a good idea to hint to the player, if he tries to take the ice chest, that there is another way to move it: Instead of taking the chest: say "It's too heavy to lift, but you might be able to push it, and just inch it over the frame of the door." Otherwise, attempts to pick it up will just reply with "That's fixed in place." Example 28 (***): Hover Letting the player see a modified room description when he's viewing the place from inside a vehicle. Suppose we want the player to see a modified room description when he's viewing the place from inside a vehicle. There are several conceivable ways of doing this; the example here shows a rather advanced way, but is very flexible and will let us write all sorts of special cases. "Hover" Use full-length room descriptions. Emerald City is a room. "All the buildings are spires and none of them have doors." The Vast Desert is west of Emerald City. "[if the player is in a vehicle]Outside, a[otherwise]A[end if] trackless waste stretches as far as the eye can see in every direction." The hover-bubble is a vehicle in the Emerald City. "Your hover-bubble awaits." The description is "The hover-bubble is a clear globe-shaped vehicle capable of transporting you anywhere you could walk, but faster." Understand "bubble" as the hover-bubble. The hover-bubble contains a chocolate wrapper and a parking ticket. Here's the tricky part, which relies on material from the chapters on Activities and Rulebooks: The container interior rule is listed before the room description body text rule in the carry out looking rules. This is the container interior rule: if the actor is the player and the player is in an enterable thing (called current cage), carry out the describing the interior activity with the current cage. Describing the interior of something is an activity. Now we've done that, we can write a "rule for describing the interior" of something, which will print whatever we like: Rule for describing the interior of the hover-bubble: say "The hover-bubble is transparent, but tints everything outside very faintly lavender." In fact, as a special refinement, we could even say: Rule for describing the interior of the hover-bubble when the hover-bubble contains more than one thing: say "The hover-bubble is transparent, but tints everything outside very faintly lavender. Beside you you can see [a list of other things in the hover-bubble]." Definition: a thing is other if it is not the player. Rule for listing nondescript items of the hover-bubble when the player is in the hover-bubble: do nothing. Test me with "get in bubble / look / west / take all / look / get out / east". And now anything that's beside us in the vehicle will be described during that first paragraph, rather than later on. Example 29 (*): Disenchantment Bay 9 Disenchantment Bay: enter the charter boat's Captain. Now finally we can put a Captain in the boat: The Captain is a man in the Cabin. "The captain sits at the wheel, steering the boat and occasionally checking the radar readout." Example 30 (*): Belfry You can see a bat, a bell, some woodworm, William Snelson, the sexton's wife, a bellringer and your local vicar here. "Belfry" The Belfry is a room. A bat is in the Belfry. The bell is in the Belfry. Some woodworm are in the Belfry. A man called William Snelson is in the Belfry. A woman called the sexton's wife is in the Belfry. A man called a bellringer is in the Belfry. In the Belfry is a man called the vicar. The indefinite article of the vicar is "your local". Test me with "look". Example 31 (**): Gopher-wood Changing the name of a character in the middle of play, removing the article. Suppose that we want a character who starts out with a general epithet ("the bearded man") but is later introduced to the player properly ("Japheth"). In that case, we want to be able to tell Inform to stop using an article once the character has been given a proper name. We can do this like so: "Gopher-wood" The Ark is a room. A bearded man is in the Ark. Instead of examining the bearded man for the first time: now the printed name of the bearded man is "Japheth"; now the bearded man is proper-named; say "You peer at him a bit more closely and realize that it's Japheth." Finally, we need to tell Inform to understand the man's name, but only when he's been introduced. For this purpose, we borrow from the chapter on Understanding: Understand "Japheth" as the bearded man when the bearded man is proper-named. Test me with "x japheth / x man / look / x japheth". Example 32 (*): Disenchantment Bay 10 Disenchantment Bay: things for the player and the characters to wear and carry. At this point we can dress both the Captain and the player with some appropriate props: The captain wears a baseball cap. The description of the cap is "It says, THE WORST DAY FISHING IS BETTER THAN THE BEST DAY WORKING." The player is carrying a backpack and a bottle of water. The player is wearing a pair of sunglasses. The description of the sunglasses is "The light off the water and the ice does get pretty bright sometimes." Example 33 (*): Disenchantment Bay 11 Disenchantment Bay: making a holdall of the backpack. If we wanted, we could make the player's backpack infinitely capacious, so: The backpack is a player's holdall. ...And now whenever the player character is unable to hold everything, he will automatically stow some of his possessions therein. This is only useful if the player doesn't have infinite carrying capacity himself, so perhaps we also need The carrying capacity of the player is 3. Perhaps mercifully, items which are worn are not counted against the player's carrying capacity. We might want to let him take advantage of that, too: The backpack is wearable. This capacity system makes a compromise between the realistic and the absurd: on the one hand, it acknowledges that people can't carry an infinite number of items in their hands, while at the same time providing a sack that can. Many games will have no use for object-juggling of this kind at all; others will want to be much more rigorous about questions of capacity and volume. Fortunately, it is easy to leave the whole business out by assigning no carrying capacity to anything. The tools to implement a more sophisticated capacity system are provided in the chapter on Units. Example 34 (***): Brown A red sticky label which can be attached to anything in the game, or removed again. "Brown" The Shipping Room is a room. The red sticky label is a thing carried by the player. The description of the red sticky label is "It reads: AIRMAIL[if the label is part of something (called the parent)]. It is stuck to [the parent][end if]." A black crate is in Shipping. The description is "A boring black crate." The brown crate is a thing in Shipping. The description is "An ordinary brown crate." After examining something when the label is part of the noun: say "A bright red sticky label is attached to [the noun]!" Here is the essential point: whenever we ATTACH LABEL TO something, it becomes part of that object. Instead of tying the red sticky label to something: now the red sticky label is part of the second noun; say "You stick [the label] to [the second noun]." And of course the label cannot be stuck to itself or to more than one thing at a time. Before tying the label to something when the label is part of something: if the label is part of the second noun: say "[The label] is already stuck to [the second noun]." instead; otherwise: say "(first freeing the label)[line break]"; silently try taking the label; if the label is part of something, stop the action. Instead of tying the red sticky label to the label: say "That would ruin the label entirely." Instead of taking the label when the label is part of something: now the player carries the label; say "You peel the label off again." Much of the rest is just tidying to make sure that the player's commands are redirected into the right syntax. Instead of tying something to the label: try tying the label to the noun. Instead of putting the label on something: try tying the label to the second noun. Instead of inserting the label into something: try tying the label to the second noun. Understand the commands "stick" or "apply" as "tie". We could have created a new "sticking" action, but to keep the example short we will use the built-in "tying" action instead, and respond to the command "stick" just as if it were "tie". Understand "peel [something]" or "peel off [something]" as taking. Test me with "i / put label on the black crate / look / x black / x label / get the label / apply label to brown crate / look / x brown / peel off label / stick label to label". Example 35 (****): Disenchantment Bay 12 A final trip to Disenchantment Bay: the scenario turned into a somewhat fuller scene, with various features that have not yet been explained. "Disenchantment Bay" Include Locksmith by Emily Short. The Cabin is a room. "The front of the small cabin is entirely occupied with navigational instruments, a radar display, and radios for calling back to shore. Along each side runs a bench with faded blue vinyl cushions[if the compartment is closed], which can be lifted to reveal the storage space underneath[otherwise], one of which is currently lifted to allow access to the storage compartment within[end if]. A glass case against the wall contains several fishing rods. Scratched windows offer a view of the surrounding bay, and there is a door south to the deck. A sign taped to one wall announces the menu of tours offered by the Yakutat Charter Boat Company." The Cabin contains a glass case. In the glass case is a collection of fishing rods. Understand "rod" as the collection. The case is closed, transparent, openable, lockable, and locked. The case is scenery. The small silver key unlocks the case. The bench is in the cabin. On the bench are some blue vinyl cushions. The bench is enterable and scenery. The cushions are scenery. A storage compartment is an openable closed container. It is part of the bench. Instead of opening the bench, try opening the storage compartment. Instead of closing the bench, try closing the storage compartment. Instead of pushing or pulling or turning the cushions, try opening the storage compartment. Understand "space" as the storage compartment. Some nets and a Coke are in the compartment. Understand "net" as the nets. The description of the nets is "They must have something to do with fish as well. Really, you're just here for the sights." The nets are a container. Some navigational instruments, some scratched windows, a radar display, and some radios are scenery in the cabin. The radar, the instruments, and the radios are devices. The radar and the instruments are switched on. A screen is part of the radar. The description of the screen is "[if the radar is switched on]Phantom lights move across the screen.[otherwise]The screen is dark.[end if]". Instead of doing something other than examining to the screen, say "It's not good for much but looking at." The Captain is a man in the Cabin. "The captain sits at the wheel, steering the boat and occasionally checking the radar readout." The captain wears a baseball cap. The description of the cap is "It says, THE WORST DAY FISHING IS BETTER THAN THE BEST DAY WORKING." The captain carries the silver key. The description of the captain is "[The captain] is wearing [a list of things worn by the captain][if the captain carries something] and carrying [a list of things carried by the captain][end if]." The description of the instruments is "Knowing what they do is the Captain's job." Instead of doing something other than examining to the instruments in the presence of the Captain: say "The Captain glares at you. Clearly you are not welcome to do that." The description of the windows is "They're a bit the worse for wear, but you can still get an impressive view of the glacier through them. There were whales earlier, but they're gone now." Understand "window" as the windows. The description of the radar is "Apparently necessary to avoid the larger icebergs." The description of the radios is "With any luck you will not need to radio for help, but it is reassuring that these things are here." A sign is scenery in the Cabin. The description is "You can get half-day and full-day sight-seeing tours, and half-day and full-day fishing trips." The view of the Malaspina glacier is a backdrop. It is everywhere. The description is "The Malaspina glacier covers much of the nearby slope, and -- beyond it -- an area as large as Rhode Island." Understand "view of the surrounding bay" or "surrounding bay" as the view. The cabin door is south of the Cabin and north of the Deck. It is a door and scenery. The description of the Deck is "The whole back half of the boat is open, allowing you to view the surroundings without intervening windows -- if you can stand the cold." The ice chest is a closed openable container in the Deck. "A very heavy ice chest sits on the ground." It is fixed in place and pushable between rooms. A quantity of ice is in the Deck. "All around the boat bob chunks of glacier ice." Understand "glacier ice" as the quantity. The description is "Curiously cooled into funny-shaped chunks." The printed name of the quantity is "glacier ice". Instead of taking the quantity of ice when the player is not carrying the nets: if the quantity of ice is handled, continue the action; say "You are having a hard time fishing out the ice with your bare hands." Instead of taking the quantity of ice when the player is carrying the nets: if the quantity of ice is handled or the quantity of ice is in the nets, continue the action; now the quantity of ice is in the nets; say "You scoop up the ice with the net." Instead of taking the chest: say "It's too heavy to lift, but you might be able to push it, and just inch it over the frame of the door." The player is carrying a backpack. The player is wearing a pair of sunglasses. The description of the sunglasses is "The light off the water and the ice does get pretty bright sometimes." The backpack is a player's holdall. The carrying capacity of the player is 3. The backpack is wearable. Instead of asking the Captain for the key: say "'Sure, you can -- well, get me a drink first, would you?'" Instead of asking the Captain for the key when the Captain is carrying a cold Coke and the Captain is carrying the key: move the key to the player; say "'Here, knock yourself out.'" Instead of asking the Captain for the key when the Captain is not carrying the key: say "'I already gave it to you. You didn't lose it, did you?'" Heat is a kind of value. The heats are cold, cool, room temperature, and warm. A beverage is a kind of thing. A beverage can be openable or unopenable. A beverage is always edible and openable. A beverage has a heat. A beverage is usually warm. The Coke is a beverage. The beer is a beverage. The beer is in the backpack. Instead of giving or showing a beer to the Captain: say "'I don't drink on the job, thanks,' he says. 'You can help yourself if you want it, though.'" Instead of giving or showing a Coke to the Captain: say "'It needs chilling,' the Captain remarks, disgruntled." Instead of giving or showing a cold Coke to the Captain: move the Coke to the Captain; increase the score by 2; say "'Ah, thank you,' he says. How he can drink an iced soda on a day like today is an open question, but Alaskans are special." Every turn when the quantity of ice is in the ice chest: repeat with item running through beverages in the ice chest: let the current heat be the heat of the item; if the current heat is not cold, now the heat of the item is the heat before the current heat. Before printing the name of a beverage (called the drink): say "[heat of the drink] ". Understand the heat property as describing a beverage. The maximum score is 5. After taking the fishing rods: end the story finally; increase the score by 3; say "Success is yours! (Now if only you knew anything about fishing.)" Test me with "test first / test second / test third". Test first with "x captain / open case / i / ask captain for the key / give beer to captain / open bench / x nets / get nets / get coke / give coke to captain". Test second with "s / open chest / drop nets / get glacier ice / get nets / get glacier ice / g / put glacier ice in chest / get coke / put coke in chest". Test third with "x coke / g / g / g / get coke / n / give coke to captain / ask captain for key / open case / get rods". Example 36 (***): Search and Seizure A smuggler who has items, some of which are hidden. Suppose we want a character who carries hidden objects, but only while he is wearing his jacket. If we deprive him of this, his other possessions become known. Furthermore, if we ever search him, his possessions also become known, and can thereafter be mentioned by us. "Search and Seizure" Size is a kind of value. The sizes are small, medium, and large. A thing has a size. A thing is usually small. A thing can be licit or contraband. A thing is usually licit. A thing can be discovered or secret. A thing is usually secret. Now, we want the character to be able to hide small things if he has some sort of concealing garment on. We also want to be able to see anything that the player has already found once, perhaps by using the >SEARCH PERSON command. So: Rule for deciding the concealed possessions of someone (called the suspect): if the particular possession is discovered, no; if the suspect wears something and the particular possession is small, yes; otherwise no. The following rule, borrowed from a later chapter, assures that any items that are ever mentioned to the player will be treated as known from then on: Before printing the name of something (called discovery): now the discovery is discovered. The Customs House is a room. The smuggler is a man in the Customs House. The smuggler wears a leather jacket. He carries a bottle of Altairan rum, some raspberries, and a laser pistol. The pistol is large. The jacket is large. The rum and the raspberries are contraband. The description of the smuggler is "He has a bestubbled chin and a sinister eye." The tourist is a woman in the customs house. The description is "The type who walks off home with a dozen contraband items in her pocket not because she means to steal things but because she's too stupid to understand that the law applies to herself." She wears a tight-fitting dress. The dress is large. The tourist carries a grapevine and an archaeological artifact. The grapevine is large and contraband. The artifact is contraband. Report examining someone: say "[The noun] is [if the noun is wearing something]wearing [a list of unconcealed things worn by the noun] and [end if]carrying [a list of unconcealed things carried by the noun]." Report examining someone who is concealing something contraband: say "[The noun] looks nervous. You can just tell." Report examining someone who is carrying an unconcealed contraband thing: say "Your eye goes at once to [the list of unconcealed contraband things carried by the noun] which [the noun] is unable to hide"; if an unconcealed licit thing is had by the noun, say ", though [if the noun is female]s[end if]he also has [a list of unconcealed licit things had by the noun]"; say "." instead. Notice that we can talk about what the smuggler wears, what he carries, and what he "has": things the smuggler has can be either worn or carried, so the phrase is useful if we don't care to make that distinction. Instead of searching someone: say "[The noun] is revealed to be carrying [a list of things carried by the noun]." Instead of confiscating the dress: say "You are not allowed to perform strip-searches in the public customs area." Understand "confiscate [something]" as confiscating. Confiscating is an action applying to one thing. Check confiscating: unless the noun is had by someone who is not the player: say "You can only confiscate other people's possessions." instead. Carry out confiscating: now the noun is carried by the player. Report confiscating: say "Through the authority vested in you by the power of the Sovereign of Centauri Proxima, you make [the noun] your own." Test me with "x smuggler / search smuggler / x smuggler / confiscate jacket / x smuggler / confiscate rum / confiscate pistol / x smuggler / confiscate raspberries / x smuggler". Test more with "x tourist / confiscate dress / confiscate grapevine / x tourist / search tourist / confiscate artifact / x tourist". Example 37 (**): Van Helsing A character who approaches the player, then follows him from room to room. Suppose we want to write a character who tries to be in the same room as the player. We will do this by testing every turn whether the character's location and the player's location are the same; if the answer is no, the character will look for a path to the player's location, then try to move along that path. (We will learn more about finding paths and giving characters instructions later.) The result will be that if the player ever moves to another location, the character will automatically pursue him. "Van Helsing" The Drawbridge is a room. North of the Drawbridge is the Immensely Enormous Entry Hall. West of the Entry Hall is the Vast Dining Area. North of the Vast Dining Area is the Colossal Kitchen. The Spooky Guano-filled Attic is above the Entry Hall. Count Dracula is a man in the Attic. In the following condition, we could also have written "if the location of Count Dracula is not the location", because "location" by itself is always understood to be the player's location. But it seemed better for clarity to write it this way: Every turn: if the location of Count Dracula is not the location of the player: let the way be the best route from the location of Count Dracula to the location of the player, using doors; try Count Dracula going the way; otherwise: say "'Muhahaha,' says Count Dracula." Test me with "z / z / n / w / e / u / z / d". Example 38 (**): Prisoner's Dilemma A button that causes a previously non-existent exit to come into being. We can change the directions in the map in mid-game, though in practice this is rarely necessary. But suppose we do not want a door or any sign of a door to exist before the player takes some action, in this case pressing a button: "Prisoner's Dilemma" Challenger's Waiting Room is a room. "The challenge is this: to wait as long as you can endure to do so in a room with no features and no clock. If you wait longer than all the other contestants, you win." The button is fixed in place in the Challenger's Waiting Room. "The only item in view is a black recessed button." Amid the Cheering Throng is a room. Instead of pushing the button for the first time: change the east exit of the Challenger's Waiting Room to Amid the Cheering Throng; change the west exit of the Cheering Throng to the Challenger's Waiting Room; say "With a groan of gears, the east wall swings open! If you've lost now, well, you've lost..." Test me with "e / push button / e / w". Our instructions about pushing the button will be further explained in the chapter on Actions, but the thing to note here is that we can "change (whatever) exit" in order to set or re-set map directions. Notice that we have to set both directions explicitly: changing the east exit of the Waiting Room does not automatically also change the west exit of Amid the Cheering Throng. This allows greater flexibility in our games but does require an extra line or so of work. Example 39 (**): The World of Charles S. Roberts Replacing the ordinary compass bearings with a set of six directions to impose a hexagonal rather than square grid on the landscape. Wargaming is an ancient pursuit, but its modern form began as a professional training exercise in 19th-century Prussian staff colleges; since at least as early as H. G. Wells's "Little Wars" (1913) it has been a hobby of "boys from twelve years of age to one hundred and fifty and for that more intelligent sort of girl who likes boys' games and books." The free-form tabletop game used miniature figures and tape-measured movements, and remains the dominant form today. But in the mid-20th century, map grids on printed sheets gave the hobby a sudden new lease of life. They were easier to set up, more interesting to look at, cheaper to sell by mail-order. 1970s sales figures for "Strategy and Tactics", the leading US subscription-based wargame distributor, were very similar to those of Infocom's IF games in the 1980s. And like classical IF, the grid-based wargame parceled up a continuous world into locations. Grids were initially square, as on a chessboard, but square cells have several disadvantages. Four directions of movement (N, E, S, W) is too few, yet allowing movement in the diagonal directions means allowing tanks to travel about 1.4 times faster northeast than they do north. Square grids also only conform cleanly to man-made landscape features such as buildings in one orientation, and they never fit hills well. (A compromise measure to fix this, cutting the squares into octagons to leave smaller diamond squares at corner intersections, has never caught on.) (Image hexes.jpg here) But following Charles S. Roberts's American Civil War designs for Avalon Hill of 1958-61 (notably "Chancellorsville" and the second edition of "Gettysburg"), a hexagonal grid became the new standard. Each hexagon is the same distance from the centre of all six of its neighbours, which are at equal angular spacings; and clumps of hexagons fit the shape of lakes, contoured hills, and so forth, much more naturally than clumps of squares do. Hexes also have a certain mystique - an air of "I don't belong in the children's department". But hexes are tricky for IF, not least because English lacks words for "the direction 60 degrees around from front". Our cognitive view of the world tends to be square, perhaps because our two eyes both face front, in a direction at right angles to the plane of our arms, legs, pelvis and eyes. We reach out sideways at right angles to our walking. Even early hex-grid wargames called the cells "squares", though "hexes" eventually caught on. Still and all: "The World of Charles S. Roberts" Forward is a direction. Forward has opposite backward. Understand "f" as forward. Backward is a direction. Backward has opposite forward. Understand "b" and "back" as backward. Forward left is a direction. Forward left has opposite backward right. Understand "fl" as forward left. Forward right is a direction. Forward right has opposite backward left. Understand "fr" as forward right. Backward left is a direction. Backward left has opposite forward right. Understand "bl" as backward left. Backward right is a direction. Backward right has opposite forward left. Understand "br" as backward right. Now to forbid the use of the compass directions: A direction can be hexagonal or squared-off. A direction is usually squared-off. Forward, backward, forward left, forward right, backward left and backward right are hexagonal. Before going a squared-off direction, say "In this hexagonally-divided landscape, squared-off directions are not allowed." instead. A slight nuisance is that, with things as they are above, typing BACKWARD produces the response "Which do you mean, backward, backward left or backward right?" To avoid that silly question, we write: Does the player mean going backward: it is very likely. Does the player mean going forward: it is very likely. And now a clump of 37 hexes, in six columns of six or seven rooms each. There are many ingenious ways we could put this map together automatically, but instead we will take a deep breath and write: E1 is forward of E2. "Open farmland." E2 is forward of E3. "The edge of woods." E3 is forward of E4. "Deep woodland." E4 is forward of E5. "Deep woodland." E5 is forward of E6. "The rear edge of woods." E6 is forward of E7. "The start of a road leading forward right." E7 is a room. "Grassland." F1 is forward of F2. "The edge of farmland." F2 is forward of F3. "The edge of woods." F3 is forward of F4. "Clearing in woods." F4 is forward of F5. "Deep woodland." F5 is forward of F6. "A road runs backward left to forward right." F6 is a room. "The edge of grassland." G1 is forward of G2. "Grassland." G2 is forward of G3. "The edge of farmland." G3 is forward of G4. "A copse of trees." G4 is forward of G5. "The backward edge of woodland." G5 is forward of G6. "A bend in the road, from backward left to backward right." G6 is forward of G7. "Open farmland." G7 is a room. "Open farmland." H1 is forward of H2. "Grassland, bordered by a hedge to the right." H2 is forward of H3. "The edge of farmland, with a hedge to forward right." H3 is forward of H4. "A copse of trees." H4 is forward of H5. "Open farmland." H5 is forward of H6. "A passing place on the road, which bends forward left to forward right." H6 is a room. "Open farmland." I1 is forward of I2. "The end of a forward road, blocked by hedges on all sides except backward." I2 is forward of I3. "A straight road runs forward to backward, with long hedges to left and right." I3 is forward of I4. "A straight road runs forward to backward, alongside a long hedge to right." I4 is forward of I5. "A straight road runs forward to backward, alongside a long hedge to right." I5 is forward of I6. "Where three roads, forward, backward left and backward right, meet. Forward right is a thick hedge." I6 is forward of I7. "Open farmland." I7 is a room. "Open farmland." J1 is forward of J2. "Dense woodland, with a hedge to left." J2 is forward of J3. "Grassland, with a hedge to left." J3 is forward of J4. "The edge of farmland, with a hedge to left." J4 is a room. "Open farmland, with a long hedge blocking movement forward left, backward left or backward." J5 is forward of J6. "A road running forward left to backward right, alongside a hedge." J6 is a room. "Open farmland." F1 is forward right of E2 and backward right of E1. F2 is forward right of E3 and backward right of E2. F3 is forward right of E4 and backward right of E3. F4 is forward right of E5 and backward right of E4. F5 is forward right of E6 and backward right of E5. F6 is forward right of E7 and backward right of E6. G1 is forward right of F1. G2 is forward right of F2 and backward right of F1. G3 is forward right of F3 and backward right of F2. G4 is forward right of F4 and backward right of F3. G5 is forward right of F5 and backward right of F4. G6 is forward right of F6 and backward right of F5. H1 is forward right of G2 and backward right of G1. H2 is forward right of G3 and backward right of G2. H3 is forward right of G4 and backward right of G3. H4 is forward right of G5 and backward right of G4. H5 is forward right of G6 and backward right of G5. H6 is forward right of G7 and backward right of G6. I3 is forward right of H3 and backward right of H2. I4 is forward right of H4 and backward right of H3. I5 is forward right of H5 and backward right of H4. I6 is forward right of H6 and backward right of H5. J5 is forward right of I6 and backward right of I5. J6 is forward right of I7 and backward right of I6. And now we have a hexagonally-gridded world. Route-finding will work; prepositional forms like "to be mapped backward left of" exist, just as they should; and in general these directions are just as good as the square ones. (The only thing which doesn't look good is the Index map, where Inform is just unable to draw a picture because it assumes a square grid. But that has no effect on play.) The landscape is much easier to navigate with a little diagram: To say legend (D - direction): let destination hex be the room D from the location; if the destination hex is nothing, say " "; otherwise say the destination hex. Carry out looking: say "[fixed letter spacing] \ [legend forward] /[line break][legend forward left] ---- [legend forward right][line break] / \[line break]--< [location] >--[line break] \ /[line break][legend backward left] ---- [legend backward right][line break] / [legend backward] \[variable letter spacing][line break]". And finally: The player is in I5. Test me with "f / forward / backward left / bl / br / br / f". Example 40 (***): Fore Understand "fore", "aft", "port", and "starboard", but only when the player is on a vessel. Suppose we want to understand shipboard directions, but only when the player is aboard a vessel. "Fore" Section 1 - Procedure The starboard is a direction. The starboard has opposite port. Understand "s" as starboard when the location is nautical. The port is a direction. The port has opposite starboard. Understand "p" as port when the location is nautical. The fore is a direction. The fore has opposite aft. Understand "f" as fore when the location is nautical. The aft is a direction. The aft has opposite fore. Understand "a" as aft when the location is nautical. Does the player mean going a nautical direction when the location is nautical: it is very likely. Index map with fore mapped as north. Index map with aft mapped as south. Index map with port mapped as west. Index map with starboard mapped as east. And we can even add new ways to talk about the ways things are mapped, borrowing from the Relations chapter. The following will allow us to us "is abaft of" as well as "is aft of": [The verb to be abaft of implies the mapped-aft-of relation.] Now, to prevent the player from using NORTH onboard ship, or AFT on land: A room can be nautical or earthbound. A room is usually not nautical. A direction can be nautical or earthbound. A direction is usually not nautical. Starboard, port, fore, aft, up, down, the inside and the outside are nautical. Before going a nautical direction when the location is not nautical, say "Nautical directions can only be used on board ship." Before going an earthbound direction when the location is nautical, say "Compass directions make no sense on board ship, but you can use [list of nautical directions] instead." instead. Section 2 - Scenario The Fish Room is aft of the Spirit Room. Starboard of the Fish Room is the After Powder Magazine. The Bread Room is aft of the After Powder Magazine. The Fish Room, the Spirit Room, the Bread Room, and the After Powder Magazine are nautical. The description of the Fish Room is "Absurd quantities of salt fish are kept here, and periodically visited by the cook or someone serving him. It is otherwise an unexceptional little chamber, so far below the waterline that there are no portholes and no external light of any kind. [paragraph break]A narrow doorway leads forward into the Spirit Room, and the After Powder Magazine is starboard." The description of the Spirit Room is "Despite its ghostly name, this is little more than a closet down at the very navel of the ship, in which alcohol is kept: both for purifying wounds and for drinking. Under normal circumstances there is a guard posted here at every hour, lest anyone take to raiding the larder. The current absence of the guard marine strikes you as a very bad sign indeed. [paragraph break]The only way out is aft." The description of the Bread Room is "The Bread Room is not only tiny from side to side and front to back: it is also about half the height of a proper room, and the floor slopes up very steeply with the curve of the hull. [paragraph break]What is kept here would not, on land, be dignified by the name of bread: it's hard tack, punishing to the teeth, dry on the tongue, and usually a home to weevils before half the journey is done. [paragraph break]More headroom, and access to the rest of the ship, lies fore through the After Powder Magazine." The description of the After Powder Magazine is "Kept in near darkness because no one with any sense would bring a naked flame down here: when necessary, it can be lit with a single small lantern made of very thick glass and sealed to keep the sparks within. Sacks of powder are passed up into the higher levels of the ship by the scrubby little boys called 'powder monkeys' -- but none such are here now." Test me with "north / aft / fore". Example 41 (**): Vouvray Adding synonyms to an entire kind of thing. The Understanding chapter lays out ways to change how the player can refer to objects, but we may not want to wait that long for some of the basic features. Here, for instance, is how to add synonyms that the player can use to refer to an entire kind of object: "Vouvray" The Wine Emporium is a room. "Set aside, you rather suspect, for tourists: this chamber is barrel-vaulted stone, lined on each side with casks of aging wine. Discarded brochures here and there advertise Wine Tours of the Loire Valley in three different languages, none of them French." A cask is a kind of thing. A cask is always fixed in place. Understand "cask" or "barrel" as a cask. Understand "casks" or "barrels" as the plural of cask. The Vouvray cask and the Muscadet cask are casks in the Wine Emporium. Test me with "get barrels / get barrel / muscadet / x casks / x muscadet cask". Example 42 (*): Odin Replacing "You see nothing special..." with a different default message for looking at something nondescript. In recent years there has been a strong trend towards providing unique descriptions for all implemented objects. Often this is a good idea, but there are also contexts in which we may want to discourage the player from looking too closely at some things and concentrate his attention on just a few interesting ones. The trick here is that leaving items completely undescribed leads to rather dull exchanges like this: >x table You see nothing special about the table. ...which can leave the player with the impression that the author was simply too lazy to describe everything. So it can be a good idea to replace that default message with a different one more appropriate to the game. For instance: "Odin" The House of a Mortal Farmer is a room. "Having two separate rooms, this house testifies to considerable wealth and success at agriculture." The Bedroom is inside from the House. A chair is a kind of supporter. A chair is always enterable. In the House are a table, two chairs, a basket, and a hearth. On the table is a loaf of bread. The description of a thing is usually "You give [the noun] a glance, but it is plainly beneath your attention." Because the description is attached to a whole kind ("thing"), it is really a blanket instruction about many objects at once. More specific instructions always override less specific ones, so we can easily make exceptions. For instance, the following will work correctly: The infant is a man in the basket. The description of the infant is "So strong and fat that you wonder whether one of your fellow gods is acquainted with the mistress of the house-- but it's no concern of yours, of course." Test me with "x table / x chair / x infant". Example 43 (*): Something Narsty A staircase always open and never openable. In a game with many staircases, we might want: A staircase is a kind of door. A staircase is always open. A staircase is never openable. Defining the staircase this way means that we will never be able to get away with (for instance) a folding ladder into the attic which is sometimes closed up. So alternatively we might do "Something Narsty" A staircase is a kind of door. A staircase is usually open. A staircase is seldom openable. We could then write a rule so that whenever the player types CLIMB [any staircase], the command is diverted to an enter command, while all other doors refuse to respond to such treatment. Still, this kind is now usable, as we see in this trivial example: The ladder is a staircase. It is above the Woodshed and below the Scary Loft. Test me with "up". But these are refinements for a later chapter. Example 44 (***): Get Me to the Church on Time Using kinds of clothing to prevent the player from wearing several pairs of trousers at the same time. Inform's default handling of wearable things does not make any rules about what can be worn together. Suppose, however, we have a game in which there are a large number of different garments, and we want to keep the player from wearing (say) more than one pair of pants at once: "Get Me to the Church on Time" A pair of pants and a shirt are kinds of thing. A pair of pants and a shirt are usually wearable. Some golf pants are a pair of pants. The description is "Checked in red and green, with tiny frolicking gophers every few inches." Some tuxedo trousers are a pair of pants. The description is "Black, pressed, and slimming." The frilly shirt is a shirt. The description of the frilly shirt is "She insisted." The polo shirt is a shirt. The description is "Turquoise and bright yellow, the colors selected by your golfing buddies." The player wears the golf pants and the polo shirt. The player carries the tuxedo trousers and the frilly shirt. The Wedding Chapel Dressing Room is a room. "The bride's dressing room is a lavish suite with closets, hangers, dressmaker's dummies, boxes of straight pins and sewing notions, combs, lotions, brushes, and hair fixatives, plus room for fifteen female attendants and a photographer. Before they shoved you out of the room you even got a glimpse of a small reference library including '1001 French Braids' and 'Corset-Lacing For Beginners.' This is the groom's dressing room. You get a framed photograph of Elvis, a dusty mirror, and the floor space of an average toilet stall." The dusty mirror and the photograph of Elvis are scenery in the Dressing Room. The description of the mirror is "You can't really get more than a silhouette impression of yourself." The description of Elvis is "He reminds you that you'd better get out there before the organist switches to Hound Dog." And now the rule itself, borrowed from a later chapter: Instead of wearing a pair of pants when the player is wearing a pair of pants (called the wrong trousers): say "You'll have to take off [the wrong trousers] first." Instead of wearing a shirt when the player is wearing a shirt (called the wrong top): say "You'll have to take off [the wrong top] first." When play begins: say "From the other side of the door, you hear the organist move on from his instrumental interpretation of 'I Wanna Hold Your Hand' to a somewhat more spirited rendition of 'Help! I Need Somebody!'. Okay, okay, but you've been rushing things along since the 16th fairway, and you can't be more than a half-hour late... Surely that mother of hers can't blame you for that?" Test me with "i / x trousers / wear trousers / x golf pants / take off golf pants / wear trousers / x frilly shirt / x polo shirt / wear frilly shirt / doff polo shirt / wear frilly shirt". If we wanted to, we could make similar kinds for hats, shoes, and so on, and have a simple but effective system of clothing. A more complicated treatment might keep track of layering and describe the player's outfit differently depending on which clothes were outermost -- an example for a later chapter. Example 45 (**): Change of Basis Implementing sleeping and wakeful states. Suppose we want to allow the player to go to sleep some of the time: "Change of Basis" A person is either awake or asleep. A person is usually awake. The important thing to note here is that it does not work to say "the player is either asleep or awake". This is because the player is not necessarily one specific person or thing during the game: the identity of the player can be changed, as we will see later. So if we want to make rules about the properties of the player, we should attach these rules to the "person" kind (or, if they really need to belong only to the player, to the "player-character" kind). A player-character is a kind of person. Linear Algebra Class is a room. "The blackboard is covered with square arrangements of numbers. These are supposed to convey something to you, but mostly you're finding them soporific." Now a few rules about changing from one state to the other: Instead of sleeping: now the player is asleep; say "You drop off." Instead of doing something other than waking up, waiting or sleeping when the player is asleep: say "Ssh! You're sleeping!" Instead of sleeping when the player is asleep: say "Zzzz." Instead of waking up when the player is asleep: now the player is awake; say "You come to suddenly, wiping drool from your lips." Instead of doing something other than looking or sleeping when the player is awake: say "You'd really rather just sleep through this." Test me with "wake up / sleep / look / z / sleep / wake up / look". Example 46 (*): Would you...? Adding new properties to objects, and checking for their presence. For instance, if we want to give some objects a flavor: "Would you...?" The House is a room. The mouse is an animal in the House. The player carries some green eggs and a ham. A food is a kind of thing that is edible. Food has some text called flavor. The flavor of food is usually "Tolerable." Things are, in general, not edible by default, so we have to make them edible specifically in order to allow them to be eaten by the player. Here we've defined food to be edible by default, and we have given it a standard piece of flavor text. The ham and the green eggs are food. The flavor of the green eggs is "Delicious!" After eating something: if the noun provides the property flavor, say "[the flavor of the noun][paragraph break]"; otherwise say "It's [noun]-flavored." Note that we use "if the noun provides a flavor..." to make sure that the property exists before attempting to use it. Otherwise, there is the risk that we will try to print a property that does not exist, resulting in errors in the game. We will only get the "It's [noun]-flavored." response if we successfully eat something that is not a food and does not have flavor text. To test this feature, let's suppose something that isn't exactly food but can theoretically be chewed on: The player carries some paper. The paper is edible. Test me with "eat ham / eat green eggs / eat paper". Example 47 (**): Straw Boater Using text properties that apply only to some things and are not defined for others. Sometimes we like to give properties to kinds of thing, but not fill them in in all cases. For instance, we might have vehicles that optionally make noise, and those might have a "movement sound". All properties have a default value, which we can find by looking in the Kinds tab of the index. This is what the property will be set to automatically, if we do not change it ourselves. In the case of a text property, that is ""; so for instance we might use our movement sound thus: "Straw Boater" Boathouse is a room. "A boathouse circa 1915, which -- though in poor repair -- still suggests Sunday afternoon jaunts taken by women in white gowns and men in straw hats." North of the Boathouse is the Shallow Water. The description of Shallow Water is "Just south is the boathouse, and beyond it are trees and the marble terrace of the house above. The water deepens to the north." North of Shallow Water is Deep Water. The description of Deep Water is "From here the boathouse has dwindled invisibly to the south, and you have a broad panorama of the shoreline, all the way down to the Skeleton Point Lighthouse in the southeast." A vehicle has some text called the movement sound. The sailboat and the motorboat are vehicles in the Boathouse. The movement sound of the motorboat is "VRRRROOOMMMM..." Understand "boat" as the sailboat. Understand "boat" as the motorboat. Note that we haven't given the sailboat any movement sound at all. After going somewhere by a vehicle (called cart): if the movement sound of the cart is not "", say "[the movement sound of the cart][paragraph break]"; continue the action. Instead of exiting when the player is in a vehicle and the location is not the Boathouse: say "You're not dressed for a swim." Instead of going somewhere when the player is not in a vehicle: say "You'd rather not try to make this journey by swimming alone." Test me with "n / get in sailboat / n / get out / s / get in motorboat / n / n". Example 48 (*): The Undertomb 1 A small map of dead ends, in which the sound of an underground river has different strengths in different caves. This example creates a kind of room, "dead end", and gives each a textual description called its "river sound". Note the use of a text substitution to fill in the appropriate river sound text in each dead end. "The Undertomb" A dead end is a kind of room with printed name "Dead End" and description "This is a dead end. You'll have to go back the way you came, consoled only by [river sound]." A dead end is usually dark. The Undertomb is a dark room. East is a dead end. South is a dead end with printed name "Collapsed Dead End". Northwest is a dead end called the Tortuous Alcove. In the Undertomb is the lantern. It is lit. A dead end has some text called river sound. The river sound of a dead end is usually "a faint whispering of running water". The Tortuous Alcove has river sound "a gurgle of running water". Test me with "get lantern / e / w / s / n / nw / se". Example 49 (**): The Undertomb 2 Flickering lantern-light effects added to the Undertomb. "Undertomb 2" Section 1 - Procedure Brightness is a kind of value. The brightnesses are guttering, weak, radiant and blazing. A brightness can be adequate or inadequate. A brightness is usually adequate. Guttering is inadequate. Temperature is a kind of value. 100C specifies a temperature. A brightness has a temperature. The temperature of a brightness is usually 700C. The temperature of blazing is 1400C. The temperature of radiant is 1100C. A dead end is a kind of room with printed name "Dead End" and description "This is a dead end, where crags in the uneven rock are caught by the [brightness of the lantern] flame you hold aloft. Despite [river sound] there is no sign of the stream." A dead end is usually dark. A dead end has some text called river sound. The river sound of a dead end is usually "a faint whispering of running water". Section 2 - Scenario The Undertomb is a dark room. "From this dim cross-groined room, exits depart east, south, and northwest." East is a dead end. South is a dead end with printed name "Collapsed Dead End". Northwest is a dead end called the Tortuous Alcove. The Tortuous Alcove has river sound "a gurgle of running water". The player carries a book. The description of the book is "[if the brightness of the lantern is adequate]Many secrets are now yours.[otherwise]No, the print's too tiny by this awful light." In the Undertomb is a lantern. It is lit. The lantern has a brightness. The lantern is blazing. The description of the lantern is "The lantern shines with a flame at [temperature of the brightness of the lantern]." After waiting in the Tortuous Alcove when the brightness of the lantern is not guttering: now the lantern is the brightness before the brightness of the lantern; say "You wait so long that your lantern dims a bit." Test me with "east / west / get lantern / east / west / south / north / northwest / read book / x lantern / z / x lantern / read book / look / z / x lantern / read book / look / z / x lantern / read book / look". Example 50 (***): Signs and Portents Signpost that points to various destinations, depending on how the player has turned it. "Signs and Portents" Seven Dials is a room. The description of Seven Dials is "There is a signpost, on which seven hands swivel and swing, freely as weathercocks. They make your present road now London, now Abingdon; now Weston-super-Mare, or now Hell." Seven Dials contains a signpost. The signpost is scenery. Understand "sign" and "post" as the signpost. Destination is a kind of value. The destinations are London, Abingdon, Luton, Weston-super-Mare, Runnymede, Hell, and Low Noon. The signpost has a destination. In order to interact with the signpost, we will need to borrow some action rules from chapter 6: Instead of examining the signpost: say "[The signpost] currently puts you on the road to [italic type][the destination of the signpost][roman type], but it swiftly alters again."; now the destination of the signpost is the destination after the destination of the signpost. Instead of turning the signpost: now the destination of the signpost is the destination after the destination of the signpost; say "With a hand's touch you turn the signpost to mark your way for [italic type][the destination of the signpost][roman type]." Instead of going north in Seven Dials when the destination of the signpost is Hell: say "It is a path that goes gently ever down and down with no stumbling block or any distraction at either side; there are no bandits and no tolls."; end the story. Instead of going north in Seven Dials when the destination of the signpost is Low Noon: say "A long road whose scenery does not change, nor anything on the horizon move but the sun. When at last you come to Noon, she hangs above your head like a hat."; end the story finally. Test me with "x signpost / n / turn signpost / n / turn signpost / n / turn signpost / n / turn signpost / n". Test more with "x signpost / n / turn signpost / n / turn signpost / n / turn signpost / n / turn signpost / turn signpost / n". Example 51 (***): The Crane's Leg 1 A description text that automatically highlights the ways in which the object differs from a standard member of its kind. When you see a long object, you don't have to think that it is too long if being long is the property given by the nature. It is proved by the fact that a duckling, having short legs, will cry if you try to draw them out by force, and that a crane, having long legs, will protest you with tears if you try to cut them with a knife. -- Zhuangzi Suppose we have an extremely detailed world model in which every object is characterized by many features -- in this example, material and height, though one could add more. Suppose further that we would like to generate descriptions of these things automatically for the most part, drawing the player's attention only to those aspects of the object that are particularly interesting. "The Crane's Leg" Material is a kind of value. The materials are wood, glass, stone, cloth, paper, clay, and metal. A thing has a material. A height is a kind of value. 3 feet 11 inches specifies a height. A thing has a height. Definition: a thing is tall if its height is 6 feet 0 inches or more. Definition: a thing is short if its height is 2 feet 0 inches or less. So far, we have generally dealt with cases where the property of a thing can be a number (such as 3), a value (such as brightness), or a unit (like height, here). It is also possible for a thing to have a property which names another thing, as in "The mother of the baby trout is the large trout" -- where "mother" is a property, and its value, in the case of the baby trout, is large trout. We would define such a property with a line such as "A fish has a thing called the mother." In practice, though, this is a bit confusing as syntax; moreover, Inform has a much more powerful construct for talking about the ways in which one object relates to another object. A full discussion of this will have to wait for the chapter on Relations. For now, it is enough to say that we can do this: Imitation relates various things to one thing (called the ideal). The verb to imitate (it imitates, they imitate, it is imitating) implies the imitation relation. This will allow us to declare that some objects imitate other objects, like so: A chair is a kind of supporter. A chair is always enterable. A chair is usually wood. The height of a chair is usually 4 feet 0 inches. The ordinary chair is a chair. Every chair imitates the ordinary chair. A table is a kind of supporter. A table is usually wood. The height of a table is usually 3 feet 8 inches. The ordinary table is a table. Every table imitates the ordinary table. A rock is a kind of thing. A rock is usually stone. The ordinary rock is a rock. Every rock imitates the ordinary rock. The height of a rock is usually 0 feet 3 inches. A jug is a kind of container. A jug is usually clay. The ordinary jug is a jug. Every jug imitates the ordinary jug. The height of a jug is usually 0 feet 8 inches. Now each of these types has one ideal representative which has the fundamental attributes of its kind: the ordinary chair is the most chairlike chair imaginable, the ordinary table is the epitome of tableness, and so on. We are also allowed to refer to "the ideal of the chair", thanks to the way we defined imitation. (Again, the relations chapter offers a much more detailed explanation of how relations may be defined.) The description of a thing is usually "[comparison with ideal][run paragraph on]". To say comparison with ideal: let the sample be the ideal of the noun; if the sample is not a thing: say "Perfectly conforming to your expectations of its type."; rule succeeds; if the material of the noun is not the material of the sample: if the height of the noun is not the height of the sample: if the noun is shorter than the sample, say "Unusually short at [height of the noun], and made of [material of the noun]."; otherwise say "Unusually tall at [height of the noun], and made of [material of the noun]."; otherwise: say "Distinct mostly in being made of [material of the noun]."; otherwise: if the height of the noun is not the height of the sample: if the noun is shorter than the sample, say "Unusually short at [height of the noun]."; otherwise say "Unusually tall at [height of the noun]."; otherwise: say "In every respect [a sample]." The Pleasure Garden is a room. "At the riverbank, a pleasing garden, having many curving paths and one straight." The low table is a table in the Pleasure Garden. The height of the low table is 2 feet 3 inches. On the low table is a metal rock called a gold nugget. Test me with "x table / x nugget". So far the effect is not very deep, but we could take the auto-description a great deal further: providing a larger and more interesting set of variations; or writing a complicated set of rules such that the player only notices height variations when carrying a ruler; or switching between several player-characters, each of whom notices a different subset of characteristics. But these refinements would require more input from later chapters. Example 52 (***): Real Adventurers Need No Help Allowing the player to turn off all access to hints for the duration of a game, in order to avoid the temptation to rely on them overmuch. Suppose we have an action called "asking for help" that gives the player some hints on request. We've also made it possible to turn this feature off, if the player would like to discourage himself from using the hints too much. Now we need a value that varies to keep track of whether hints are currently permitted or currently not permitted. So we might write: "Real Adventurers Need No Help" A permission is a kind of value. The permissions are allowed and denied. Hint usage is a permission that varies. Hint usage is allowed. And under the right circumstances, we change hint usage to denied: Check asking for help for the first time: say "Sometimes the temptation to rely on hints becomes overwhelming, and you may prefer to turn off hints now. If you do so, your further requests for guidance will be unavailing. Turn off hints? >"; if player consents: now hint usage is denied; say "[line break]Truly, a real adventurer does not need hints." instead. Then we can refer back to this value later to decide whether we want to display the hint menu or not: Check asking for help: if hint usage is denied, say "You have chosen to eschew hints in this game. Be strong! Persevere!" instead. Asking for help is an action out of world. Understand "help" or "hint" or "hints" as asking for help. The Realm of Terribly Unjust Puzzles is a room. Carry out asking for help: say "Fine, since you're weak enough to ask: here is a complete walkthrough: GET EGG. PEEL EGG. SMELL EGG. DIVIDE YOLK INTO THREE PORTIONS. GIVE THE SMALLEST PORTION OF YOLK TO THE GOLDEN GOOSE. ASK THE GOOSE ABOUT WHETHER THE SWAN IS TO BE TRUSTED. GIVE THE LARGEST PORTION OF YOLK TO THE SWAN. DANCE CONGA. EAT MEDIUM PORTION. STAND ON HEAD. WEST." Test me with "hint". Note that it would probably be kinder to offer the player some intermediate level of help, in the actual event. Example 53 (***): Early Childhood A child's set of building blocks, which come in three different colours - red, green and blue - but which can be repainted during play. This would be a one-star example if it were not for the repainting: "Early Childhood 1" A building block is a kind of thing. A red block, a blue block and a green block are kinds of building block. The Nursery is a room. In the Nursery are six red blocks, four blue blocks and a green block. Test me with "look / get red block". But a kind cannot change during play, so this will not do. Instead, the colour will have to be a property of the block. So we might first try this: "Early Childhood 2" Colour is a kind of value. The colours are red, blue and green. A block is a kind of thing. A block has a colour. A block is usually blue. The Nursery is a room. In the Nursery are six red blocks, four blue blocks and a green block. Test me with "look / get red block". Which is fine, so far as it goes, but the colour property is not at all visible to the player, who simply sees "eleven blocks". We thought of colour as being something outwardly apparent, but Inform does not know this. To achieve a better effect, we will need features from distant chapters. The first is an activity called "printing the name of": "Early Childhood 3" Colour is a kind of value. The colours are red, blue and green. A block is a kind of thing. A block has a colour. A block is usually blue. Before printing the name of a block: say "[colour] ". Before printing the plural name of a block: say "[colour] ". The Nursery is a room. In the Nursery are six red blocks, four blue blocks and a green block. Test me with "look / get red block". This too, however, is unsatisfactory. The individual blocks are correctly described, but we are unable to distinguish them during play: we cannot type "take a green block", for instance. And because the blocks are indistinguishable in play, they are still massed together as "eleven blocks" in room descriptions. We need to go one step further: "Early Childhood 4" Colour is a kind of value. The colours are red, blue and green. A block is a kind of thing. A block has a colour. A block is usually blue. Before printing the name of a block: say "[colour] ". Before printing the plural name of a block: say "[colour] ". Understand the colour property as describing a block. The Nursery is a room. In the Nursery are six red blocks, four blue blocks and a green block. And now everything works nicely: the blocks are grouped by colour, and can be referred to by colour, and we can even change the colour of an individual block during play, using a bit of extra trickery from later: Understand "paint [something] [colour]" as painting it. Painting it is an action applying to one thing and one colour. Check painting it: if the noun is not a block, say "Paints are only for blocks." instead. Carry out painting it: now the colour of the noun is the colour understood. Report painting it: say "The block is now [the colour of the noun]." Test me with "get red block / get blue block / g / i / look / paint blue block red / i / look / paint me red". Example 54 (*): Being Prepared A kind for jackets, which always includes a container called a pocket. "Being Prepared" A jacket is a kind of thing. A jacket is always wearable. A pocket is a kind of container. A pocket is part of every jacket. The carrying capacity of a pocket is always 2. After examining a jacket: let target be a random pocket which is part of the noun; say "[The target] contains [a list of things in the target]." Now we've created the rules that will govern any specific jackets we might happen to put in our game: each one will always have one pocket, which will be able to contain no more than two things. The description of "a list of things" is text with a list, which we will learn about further in a few sections. Next we might want to create the environment and an actual example of the jacket kind: Tent is a room. "A dome made of two flexible rods and a lot of bright green ripstop nylon. It bills itself as a one-man tent, but you'd call it a two-dwarf tent: there is no way to arrange yourself on its square floor so that you can stretch out completely." The hoodie is a jacket. "Your hoodie is balled up in the corner." The description of the hoodie is "Both elbows are stained from yesterday's entrenching project." The hoodie's pocket contains a Swiss army knife and a folded map. The hoodie is in the Tent. Notice that, since Inform has created a pocket for the hoodie, we can now refer to it by name in our source, giving it any additional properties we need to define. Here we simply put a few items into it. The player wears a whistle. The description of the whistle is "To frighten bears." Test me with "x hoodie / get hoodie / get knife / get map / i / put hoodie in pocket / put whistle in pocket / put map in pocket / put knife in pocket / i". Notice that Inform automatically refuses to put the hoodie into its own pocket: as a default, a container cannot contain something of which it is itself a part. Example 55 (**): Model Shop An "on/off button" which controls whatever device it is part of. Suppose we're particularly mechanically-minded and would like a game in which all of our mechanical devices have buttons to turn them on and off. "Model Shop" An on/off button is a kind of thing. Instead of pushing an on/off button which is part of a switched off device (called the machine): try switching on the machine. Here we are making a rule about how our hypothetical buttons will interact with the machines to which they belong. Instead of pushing... is a rule that pertains to actions, and we will learn more about these in the chapter on actions. "...which is part of a switched off device" provides a specific circumstance - this is only to apply to buttons that are stuck to a machines that can be turned on or off. "(called the machine)" tells Inform that if it finds such a device, it should thereafter refer to it as "the machine." (The called syntax is explained further in the chapter on Change.) A set of three more rules will complete our instructions about using buttons to control devices: Instead of pushing an on/off button which is part of a switched on device (called the machine): try switching off the machine. Instead of switching on an on/off button which is part of a device (called the machine): try switching on the machine. Instead of switching off an on/off button which is part of a device (called the machine): try switching off the machine. Then we hand out buttons with a free hand: One on/off button is part of every device. The Model Shop is a room. A model train is a fixed in place device in the Model Shop. A toy elephant is a device in the Model Shop. Every turn when the model train is switched on: say "The model train circles your feet, blowing small puffs of steam." Every turn when the toy elephant is switched on: say "The toy elephant waves its trunk at you." Test me with "push model train's button / push elephant's button / g / switch off model train's button". And now the game will have a model train's button and a toy elephant's button. It may be that we want (as an added nuance) to add other names for these items. While we would want an assembly to create objects such as "Lucy's hand" and not "Lucy hand", it is entirely reasonable to want to talk about the model train button or the elephant button. We could define these additional names like so: Understand "elephant button" or "button on elephant" as the elephant's button. Understand "model train" or "model" or "train" as "[train]". Understand "[train] button" or "button on [train]" as the model train's button. In the second case, we are defining [train] to mean any of the three phrases "train", "model", and "model train"; so "[train] button" will match "model train button" or "train button" or "model button" equally well. See the chapter on Understanding for more on how to create alternative phrasings for the player to use. Example 56 (***): The Night Before Instructing Inform to prefer different interpretations of EXAMINE NOSE, depending on whether the player is alone, in company, or with Rudolph the Red-nosed Reindeer. Suppose that we're going to give every person in the game a nose, but we want references to a nose always to mean the nose of someone *else*, if the player is with one other person. Moreover, on some occasions we're going to be in sight of Rudolph, so actions directed at an unspecified nose should always prefer his. This relies on a somewhat advanced technique from the Understanding chapter, but since it may become useful with assemblies and body parts, it is worth mentioning here. "The Night Before" The North Pole is a room. "Here it is: the famous Pole. From here you can go south (or south-south, or south-south-by-south); or, alternatively, take refuge inside a red-and-white-striped cabin." The cabin is scenery in the North Pole. Instead of entering the cabin, try going inside. Santa is a man in the North Pole. "Santa is pacing around in the snow and trying to psych himself up for the big night." Inside from North Pole is the Candy Cane Cabin. The description of the Cabin is "Striped red and white, but nothing can make this place seem warm and inviting since Mrs. Santa ran off with the Tooth Fairy." The Ice Shelf is south of North Pole. "The ice here has been smoothed into a kind of runway for easy take-off, and ends in a cliff and cold arctic sea." Donner, Vixen, Blixen, and Rudolph are animals in the Ice Shelf. A nose is a kind of thing. A nose is part of every person. The description of Santa's nose is "It's a bit ruddy. You don't like to mention it, but Santa's been dipping heavily into the Grey Goose since Mrs. Santa left town." The description of a nose is usually "Not terribly exciting." The description of Rudolph's nose is "See how it glows!" Next, we'll teach Inform some vocabulary to distinguish between the player and everyone else: Definition: a person is other if it is not the player. Definition: a thing is selfish if it is part of the player and the player can see an other person. Instead of examining a selfish nose: say "You cross your eyes, but can't get a good look." Here is the part that actually determines the preferences. "Does the player mean..." can result in five outcomes: "it is very unlikely", "it is unlikely", "it is possible" (the neutral default), "it is likely", and "it is very likely". This is discussed in greater detail in the Understanding chapter. Here, we want to discourage references to the player's own nose and encourage references to the nose of Rudolph, so: Does the player mean doing something when the noun is a selfish nose or the second noun is a selfish nose: it is very unlikely. Does the player mean doing something to Rudolph's nose: it is very likely. And this part is just for decoration: Rule for writing a paragraph about Rudolph: say "The reindeer are already harnessed and waiting impatiently. The brilliance of [Rudolph]'s nose casts an eerie red glow over [the list of unmentioned animals in the location]." Test me with "x nose / x my nose / x santa's nose / in / x nose / out / s / x my nose / x nose / x rudolph's nose / x donner's nose". Example 57 (***): U-Stor-It A "chest" kind which consists of a container which has a lid as a supporter. Suppose we want to write a game in which there are a number of chests. Each of these chests will be a container, but have a lid which is a supporter. "U-Stor-It" Section 1 - Assemblies and Supporters A chest is a kind of container. A chest is always openable. A chest is usually fixed in place. A chest is usually closed. The specification of a chest is "Represents a container with a separately implemented lid; the lid is itself a supporter." A lid is a kind of supporter. A lid is part of every chest. The specification of a lid is "A supporter attached to a chest, which can only support things when the chest is closed." (The "specification" of a kind is not really a property, and is used instead to describe the kind in the Index. So the text of these specifications is never found in the game.) Of course, this doesn't get us very far. We will also want the game to correctly interpret variations on "open the chest" and "close the lid", redirecting actions appropriately. Section 2 - Opening and closing Before opening a lid which is part of a chest (called the item): try opening the item instead. Before closing a lid which is part of a chest (called the item): try closing the item instead. Before opening a chest when something is on the lid (called the obstruction) which is part of the noun: repeat with item running through things on the obstruction: say "(first removing [the item])"; try taking the item. Instead of opening a chest when something is on a lid (called the item) which is part of the noun: say "You'd have to remove [the list of things on the item] from the lid first." instead. Instead of looking under a lid which is part of a chest (called the item): try opening the item. We may also want to be able to deal with "put in" and "put on" appropriately, even if the player names the wrong part of the object: Section 3 - Insertion and Support Before inserting something into a lid which is part of a chest (called the item): try inserting the noun into the item instead. Before putting something on a chest when a lid (called the item) is part of the second noun: try putting the noun on the item instead. Furthermore, we don't want the player to be able to put things on the lid while the chest is open: Before putting something on a lid which is part of an open chest (called the item): say "(first closing [the item])"; try closing the item. Instead of putting something on a lid which is part of an open chest (called the item): say "[The item] would need to be closed first." And then we may also want a couple of rules for describing our assembled object nicely: Section 4 - Description in Rooms Instead of examining a closed chest when something is on a lid (called the top) which is part of the noun: say "[The noun] is closed, and there [is-are a list of things on the top] on top." After printing the name of a chest (called the item) while listing contents of a room: if a lid (called the second item) which supports something is part of the item: say " (on which [is-are a list of things on the second item])"; omit contents in listing. Now we are free to create entire treasure rooms at a single blow: Section 5 - U-Stor-It Facility The U-Stor-It Facility is a room. The sea trunk, the shipping crate, and a metal box are chests in the U-Stor-It Facility. The metal box contains a sapphire, a gold coin, and a signed photograph of Babe Ruth. Even though we have never explicitly defined it, the metal box has a "metal box's lid", which we can use at need. The metal box's lid supports a small card. The description of the small card is "It reads, 'Back in 5 mins - Pandora.'" Test me with "open trunk / x card / open metal box / put all in metal box / get card / put card on box". Example 58 (*): Bic Testing to make sure that all objects have been given descriptions. It may occasionally be useful to check whether all objects in our game have a given property. Here we have a "not for release" section that will run at the start of the game and alert us to any objects lacking description: "Bic" Section 1 - Testing descriptions - Not for release When play begins (this is the run property checks at the start of play rule): repeat with item running through things: if description of the item is "": say "[item] has no description." Section 2 - Story The Staff Break Room is a room. The player carries an orange, a Bic pen, and a napkin. The description of the orange is "It's a small hard pinch-skinned thing from the lunch room, probably with lots of pips and no juice." The description of the napkin is "Slightly crumpled." Example 59 (***): Fallout Enclosure Adding an enclosure kind that includes both containers and supporters in order to simplify text that would apply to both. It may not be immediately obvious why we might want to create new intermediate categories of the kinds hierarchy. But there may be times, for instance, where we would like to make an action that applies in the same way to both containers and supporters, but to nothing else in the game. To avoid creating two nearly-identical rules, we would instead roll the two categories together into one, on the principle that duplicating source text is usually a sign of bad design. So for instance let's say the player is able to zap objects to make them go away, but any contents -- things inside a container or on top of a supporter -- should always be left as residue. Here's one way we might do this: "Fallout Enclosure" Section 1 - Procedure Include Plurality by Emily Short. An enclosure is a kind of thing. A container is a kind of enclosure. A supporter is a kind of enclosure. Understand "zap [something]" as zapping. Zapping is an action applying to one thing. The Zapping action has a list of things called the remnants. Carry out zapping an enclosure: if the noun holds something: now the remnants is the list of things held by the noun; repeat with N running through the remnants: move N to the holder of the noun. Carry out zapping: remove the noun from play. Report zapping: say "You zap [the noun], destroying [it-them][if the remnants is not empty] and leaving [the remnants with indefinite articles] behind[end if]." Section 2 - Scenario SuperDuperMart is a room. SuperDuperMart contains some shelves and a cash register. The shelves support a bottle of Buffout and a container of Jet. The cash register contains some prewar money, a coin purse, and a bottle cap. The coin purse contains a prewar nickel. It is closed. The cash register is closed and locked. Test me with "zap shelves / zap buffout / zap register / zap purse". Example 60 (***): Ballpark A new "to say" definition which allows the author to say "[a number in round numbers]" and get verbal descriptions like "a couple of" or "a few" as a result. Sometimes it is more sensible to describe numbers roughly than in exact terms. For instance, we might want to have our player perceive "many people" rather than "forty-two people" on entering a room. To achieve this, we might write our own "to say" phrase. "Ballpark" To say (count - a number) in round numbers: repeat through the Table of Numerical Approximation: if count is less than threshold entry: say "[approximation entry]"; rule succeeds. Phrases will be explained more thoroughly in a later chapter, but as we have already seen in the examples, we can make a "To say..." phrase that will allow us to create our own text substitutions. In this case, we are going to replace the specific number with a vaguer one chosen from a chart, so: Table of Numerical Approximation threshold approximation 1 "no" 2 "one" 3 "a couple of" 6 "a few" 11 "some" 21 "many" 1000 "lots and lots of" The idea here is that we will work our way through the table until we hit a line where the threshold number is higher than the number we want to express, and then print that output: so if we have less than one item, we'll print "no"; if we have more than none but less than two, we'll print "one"; if we have less than three, we'll print "a couple of"; if we have three, four, or five (but not six), we'll print "a few." A room has a number called the population. The population of a room is usually 0. The description of a room is usually "You observe [population of the location in round numbers] [if population of the location is 1]person [otherwise]people [end if]here.". The Stadium is a room. The Hot Dog Stand is west of the Stadium. The Women's Restroom is south of the Stadium. The population of the Stadium is 500. The population of the Hot Dog Stand is 3. The population of the Restroom is 750. Test me with "w / e / s". Example 61 (*): Control Center Objects which automatically include a description of their component parts whenever they are examined. It is straightforward to make a rule that anything with parts must mention all those parts during an EXAMINE command: "Control Center" After examining a thing when something is part of the noun: say "[The noun] includes [a list of things which are part of the noun]." The Control Center is a room. "Here you are at the Control Center of the universe." The Universe Management Computer is a fixed in place thing in the Control Center. "The Universe Management Computer sits directly before you, unguarded." The description of the Universe Management Computer is "The computer is so large that you would be unable to operate it all from one position. Alas, it does not come with a manual." A chartreuse indicator light, an ennui meter, a golden knob settable to 15,000 positions, a toothpick dispenser, and a button labeled RESTART are part of the Universe Management Computer. The command chair is an enterable supporter in the Control Center. It is pushable between rooms. "Because the computer is too large for you to reach all of the front panel from a standing position, there is a command chair on casters which allows you to push back and forth." The description of the command chair is "Quite ordinary, really, but for the heady rush of power that comes of sitting in it.". Some casters are part of the command chair. Now whenever we look at any object with components, we will first see the description, then a list of parts which belong to it. The following refinement brings in elements of later chapters, but it may be worth noting: because we've written our rule as an "After examining...", anything that pre-empts the operation of the examine command will also prevent that rule from occurring. So for instance: A hair-thick needle is part of the ennui meter. Instead of examining the ennui meter: say "You can't be bothered." ...would not result in the needle being mentioned. Test me with "x chair / x computer / x ennui meter" Example 62 (**): Tiny Garden A lawn made up of several rooms, with part of the description written automatically. Sometimes we want to make a list of something too complicated to express in a say list... phrase. When this happens, we can instead mark all the items we want to mention as "marked for listing". In this case, we have a lawn area made up of four rooms. We want each room to automatically describe the directions leading to the other parts of the lawn. To do this, we will first determine which directions are relevant and mark those for listing, then list them. "Tiny Garden" The Herb Garden is a room. "Along this side of the house run your great-aunt's herb beds." A Grassy Room is a kind of room. The printed name of a Grassy Room is usually "Lawn". The description of a Grassy Room is "The grass underfoot is thick and green. The lawn extends to [grassy directions] from here." The following phrase goes through all the directions in the compass and marks the ones that are interesting to us at the moment. We will learn more about "the room (some direction) from..." in Chapter 5, and repeating in Chapter 10. To say grassy directions: repeat with that way running through directions: if the room that way from the location is a grassy room, now that way is marked for listing; say "[a list of directions which are marked for listing]"; now every direction is not marked for listing. Lawn1 is west of the Herb Garden. It contains a picnic table and a wicker basket. Lawn2 is south of Lawn1 and southeast of Lawn4. Lawn3 is southwest of Lawn1, west of Lawn2, and south of Lawn4. Lawn4 is west of Lawn1. Lawn4 contains a birdbath. The birdbath is fixed in place. Lawn1, Lawn2, Lawn3, and Lawn4 are Grassy Rooms. Test me with "w / s / w / n". Example 63 (*): When? A door whose description says "...leads east" in one place and "...leads west" in the other. Very simple, but quite frequently useful: "When?" The temporal vortex is an open door. It is west of Yesterday and east of Today. "A whirling temporal vortex leads [if the player is in Yesterday]west[otherwise]east[end if]." Example 64 (***): Persephone Separate the player's inventory listing into two parts, so that it says "you are carrying..." and then (if the player is wearing anything) "You are also wearing...". If we wanted, we might replace the rule for taking inventory as follows: "Persephone" Instead of taking inventory: say "You're carrying [a list of things carried by the player][if the player wears something]. You are wearing [a list of things worn by the player][end if]." The Fancy Party is a room. The player carries a sword, a strawberry stem, and 20 credits worth of platinum. The player wears a sash indicating lordhood. Test me with "i / take off sash / i". Example 65 (***): Whence? A kind of door that always automatically describes the direction it opens and what lies on the far side (if that other room has been visited). It would be fairly tedious reading to have a large game full of doors that describe themselves this way. Nonetheless, if we insisted we could use our knowledge of the map as leverage to make every door in the game describe itself automatically. To do this, we make use of the phrase "direction of (the door) from (a room)" -- in this case, the direction of the door we're looking at when viewed from the player's location. Thus: "Whence?" The temporal vortex is an open door. It is west of Yesterday and east of Today. The initial appearance of a door is usually "Nearby [an item described] leads [if the other side of the item described is visited][direction of the item described from the location] to [the other side][otherwise][direction of the item described from the location][end if]." Test me with "w / e". Yet a further variation on this, which can automatically understand "the east door" and "the west door" when appropriate, may be found in the example "Whither?". Example 66 (*): Radio Daze A radio that produces a cycle of output using varying text. "Radio Daze" by Jon Ingold The Living Room is a room. "A long couch, set up so you can see your wireless set. Not that you need to see it, of course." The long couch is an enterable scenery supporter in the living room. Instead of entering the long couch when the radio was switched off, say "Better turn the radio on before you get comfortable." Report entering the couch: say "You settle yourself down to listen." instead. Instead of listening when the radio is switched on, stop the action. The radio is a device in the living room. The radio is switched off. "[if switched on]The radio burbles on[otherwise]The radio is off[end if]." Check switching off the radio when the player is on the long couch: say "You can't reach the radio from here." instead. Every turn when the radio is switched on: say "[one of]Two characters in the radio play have begun an argument[or]The argument continues[or]The play continues[stopping]: [one of]'Did not!'[or]'Did too!'[or]'Did I?'[or]'You did!'[or]'I couldn't have, Martha!'[or]'But you did, Tom!'[cycling]" Test me with "sit on couch / turn on radio / sit on couch/ listen / g / g / g / g / g". Example 67 (**): Camp Bethel Creating characters who change their behavior from turn to turn, and a survey of other common uses for alternative texts. "Camp Bethel" Camp Bethel Kitchen is a room. One use for text alternatives is to change the description of a room after first visiting. We've already seen, in the example "Slightly Wrong", how to do this with "[if visited] ... [otherwise] ... [end if]". But since the first description is printed once and the second description on all subsequent occasions, we could equally well write The description of Camp Kitchen is "[one of]You've never been into the kitchen before, though you've spent many an hour in the dining lodge. The place is larger than you would have expected, and it has none of the fake rustic touches of the rest of the camp[or]A tidy, efficient industrial kitchen, without any of the kitsch rusticity found elsewhere[stopping]." We might also want to liven up the behavior of people and animals, who are probably not doing the exact same thing every time we glance in their direction. There are more complex techniques for modeling the behavior of characters, as we will see in the chapters on Advanced Actions and Activities; but if we just want some textual variety, we might write something like: Jeremy is a man in the Camp Bethel Kitchen. "Jeremy stands at his station, [one of]peeling white onions[or]briskly dicing onions[or]chopping celery[or]peeling carrots[or]tying fresh herbs together with string[or]putting all the vegetables into a large stock pot[or]watching over his boiling vegetable stock[cycling]." And since (textual variation or not) we do want the player to be able to see all these objects: Jeremy carries white onions, celery, carrots, and herbs. Jeremy's station is scenery in the kitchen. It is a supporter. Jeremy is following a sequence of actions to do an implied task (still somewhat robotically, but it will do for now). Animals might be a bit more capricious, though: Fluffy is an animal in the Camp Bethel Kitchen. "[one of]Fluffy is chasing its tail[or]Fluffy is staring out the window[or]Fluffy is rubbing itself against your leg[purely at random]." A housefly is an animal in the Camp Bethel Kitchen. "A large housefly [one of]lands on a countertop[or]flies around noisily[or]circles Jeremy's chef hat[at random]." The housefly's description is merely "at random" rather than "purely at random" because we want to show it doing a different thing each turn, whereas Fluffy could plausibly stare out the window for five turns in a row. There are more complex ways to change and override the initial descriptions of people and things; if text alternatives do not get us far enough, we can turn to the "rule for writing a paragraph about," documented in the Activities chapter. Another frequent use of text alternatives is to give characters a bit of variety in things they're likely to say many times in the course of a game: Instead of telling Jeremy about something: say "Jeremy looks [one of]surprised[or]intrigued[or]nonplussed[at random]. '[one of]You don't say[or]That's very interesting[or]Do go on[or]I wish I'd known that sooner[at random]!'". Or, with somewhat more complexity: Instead of asking Jeremy about something: say "'[one of]Sorry,[or]I'm afraid[or]Hm,[at random] [one of]I don't know much about that[or]you've got me there[or]I haven't the faintest[at random],' Jeremy [one of]drawls[or]replies[or]comments[or]exclaims[at random]"; say "[one of][or] huskily[or] throatily[or] silkily[or] in a deep manly voice[as decreasingly likely outcomes]." Notice that, in that last line, our first option is entirely blank. If we put nothing as an element of the text alternatives list, this means that printing nothing at all is a viable alternative. In fact, we've made this the most common probability out of the decreasingly likely outcomes, so that five times in fifteen, or a third of the time the text is run, there will be no modifier printed at all. Test me with "look / g / g / g / ask Jeremy about his feelings for me / ask jeremy about his amnesia / tell Jeremy about my unborn child". As this example (alas) reveals, text alternatives will not go all the way toward making our characters into compelling conversationalists; we will have to wait until we know more about Actions. But at least we have abolished the default responses, and given Jeremy a touch of personality, however witless. Example 68 (**): Beekeeper's Apprentice Making the SEARCH command examine all the scenery in the current location. We have to create a suitable action and say what it does, and to repeat what we do through all the scenery items. That needs material from subsequent chapters, but is quite ordinary Inform all the same: "Beekeeper's Apprentice" Studying the vicinity is an action applying to nothing. Report studying the vicinity: if the location does not contain something which is scenery: say "There's little of interest in the [location]." instead; repeat with point of interest running through scenery in the location: say "[point of interest]: [run paragraph on]"; try examining the point of interest. Understand "search" as studying the vicinity. The Yard is a room. The hive and the honey are scenery things in the Yard. The description of the hive is "The honeycombed hive is all around you, thrumming with life." The description of the honey is "Wax-sealed honey has been cached in many of the hexagonal nurseries." Test me with "search". The reason for this example is to show the use of saying "[run paragraph on]". It means we have output such as: >search hive: The honeycombed hive is all around you, thrumming with life. honey: Wax-sealed honey has been cached in many of the hexagonal nurseries. Without the running on, the prompts "hive:" and "honey:" would be separated from the descriptions following them, which would look a little odd. Example 69 (*): Garibaldi 2 Adding coloured text to the example of door-status readouts. The extension "Basic Screen Effects" provides a few more type styles, in the form of coloured lettering. The colours available are red, yellow, green, blue, white, magenta, and cyan, as well as the usual black; and to restore the player's default screen colour, we say "default letters". Thus if we wanted to highlight locked and unlocked doors in our security readout example: "Garibaldi" Include Basic Screen Effects by Emily Short. The security readout is a device. The description of the readout is "The screen is blank." Instead of examining the switched on security readout: say "The screen reads: [fixed letter spacing]"; say line break; repeat with item running through doors: say line break; say " [item] ([front side of the item]/[back side of the item]): [if the item is locked][green letters]LOCKED[default letters][otherwise][red letters]UNLOCKED[default letters][end if]"; say variable letter spacing; say paragraph break. The player carries the security readout. The Docking Bay is a room. The inner airlock is a door. It is north of the Docking Bay and south of the Zocalo. The inner airlock is lockable and unlocked. The outer airlock is lockable and locked. It is a door. It is south of the Docking Bay and north of Space. The quarantine seal is a door. It is west of the Zocalo and east of Medlab. Quarantine seal is locked. The security pass unlocks the inner airlock. The player carries the security pass. Test me with "x readout / turn on readout / x readout / lock inner airlock with security pass / x readout". Note that this extension does not currently produce the desired effects when compiling with the Glulx setting; to see it working, make sure that the settings tab is set to compile to z5 or z8. Example 70 (***): The Über-complète clavier This example provides a fairly stringent test of exotic lettering. The following example puts Inform's support for exotic lettering through its paces. It was useful in testing Inform but is not a very instructive read: still, it does provide a test story file for interpreters, so we are including the source here as an example. "The Über-complète clavier" The story headline is "Pushing the Limits of Unicode in IF". The story description is "This is a demanding test for Unicode compliance by Z-machine interpreters." Include Unicode Character Names by Graham Nelson. Include Basic Screen Effects by Emily Short. The Château Bibliothèque Français is east of the Deutsche Universität Bücherei. "From this Borgesian construction, doorways lead into anterooms in each of the four cardinal directions." South of the Bibliothèque is the Miscellany Mañana. North of the Bibliothèque is the Íslendingabók. East of the Bibliothèque is Alphabet Soup. A framed photograph of Icelandic Prime Minister Halldór Ásgrímsson, a ruler measuring Ångströms, a Bokmål-Lëtzebuergesch Lëtzebuergesch-Bokmål dictionary and a ticket to Tromsø via Østfold are in the Íslendingabók. A paper by Karl Weierstraß, a general feeling of Ärger, an old Österreich passport and the Bach Clavier-Übung open at the fugue à 4 are in the Bücherei. The painting of École normale superiéure students singing Ça ira, the frankly lesser-known journal of Niccolò Polo, Così fan tutte on CD, an extract of Herodotus concerning Artaÿctes and the exit sign reading À BIENTÔT are in the Bibliothèque. A wicker basket marked CHLOË is in the Bibliothèque. A ginger cat is in the basket. A guide to Æsop for naïve æsthetes, Lönnrot's Kalevala, a creed according to the Bahá'ís, FALARÃO magazine, an Estonian poem by Tõnu Trubetsky, a Portuguese-Italian recipe for macarrão, a stripy hanging CANDY PIÑATA bag, a ¿¡Punctuation Turned Upside Down¿¡ pamphlet, an Italian brewers' anti-violence poster declaring BÓTTE NON BÒTTE, a map of È and a dusty book titled The Parnasum of Luís Vaz bearing CAMÕES on its spine are in Miscellany Mañana. The description of the map is "È is a province in the People's Republic of China." In Mañana is something called ÂÊÎÔÛ - The Official Journal of the Society for Vowels bearing Circumflexes. In Mañana is something called âêîôû comic - the youth edition. The description of Alphabet Soup is "A bewildering place of glyphs, sigils and signs. The Library proper leads back west: steps lead upwards to an Observatory, or downwards into what seems to be a dangerous area. A gaming lounge lies to the south." The Greek Alphabet, the Cyrillic Alphabet, the Hebrew alphabet, and the embossed plaque are in Alphabet Soup. The description of the Greek alphabet is "αβγδεζηθικλμνξοπρςστυφχψω.". The description of the Hebrew alphabet is "אבגדהוזחטיךכלםמןנסעףפץצקרשת.". The description of the Cyrillic alphabet is "абвгдежзийклмнопрстуфхцчшщъыьэюя.". Instead of examining the plaque: say "It seems to be a sign in Braille: "; say unicode Braille pattern dots-24, " (I), ", unicode Braille pattern dots-1345, " (N), ", unicode Braille pattern dots-124, " (F), ", unicode Braille pattern dots-135, " (O), ", unicode Braille pattern dots-1235, " (R), ", unicode Braille pattern dots-134, " (M)." The Gaming Lounge is south of Alphabet Soup. The chess position and the book of puzzle canons are in the Gaming Lounge. The Georges de la Tour painting Le Tricheur is in the Gaming Lounge. "Hanging on one wall is Georges de la Tour's masterpiece Le Tricheur (the card-sharp). Visible are 8[unicode black diamond suit], 9[unicode black diamond suit], A[unicode black diamond suit], A[unicode black spade suit], 6[unicode black club suit] but not one of them has a [unicode black heart suit]." The description of Le Tricheur is "If they'd been dice-players instead, they might have thrown [unicode die face-1], [unicode die face-2], [unicode die face-3], [unicode die face-4], [unicode die face-5] or[unicode die face-6], but as it is they stick to cards. Just as well: under Mac OS X, some of those dice have the wrong number of dots!" The description of the book of canons is "A typical fugue is no. 13 (Tovey: [unicode eighth note] = 110) in F[unicode music sharp sign] minor, but you can also make out keys like A[unicode music flat sign] and G[unicode music natural sign]." The empty square text is text that varies. To say empty: say the empty square text. To display the board: say empty, empty, empty, empty, empty, empty, unicode black chess king, empty, line break; say empty, empty, empty, unicode black chess queen, empty, empty, unicode black chess pawn, empty, line break; say unicode black chess pawn, empty, empty, unicode black chess bishop, unicode black chess pawn, empty, empty, unicode black chess pawn, line break; say empty, empty, empty, unicode black chess pawn, empty, unicode black chess rook, empty, empty, line break; say empty, unicode black chess pawn, empty, unicode white chess pawn, unicode black chess pawn, empty, empty, empty, line break; say empty, empty, empty, unicode black chess bishop, unicode white chess queen, empty, unicode white chess pawn, unicode white chess pawn, line break; say unicode white chess pawn, unicode white chess pawn, empty, unicode white chess bishop, empty, unicode black chess rook, unicode white chess bishop, empty, line break; say empty, unicode white chess knight, empty, empty, unicode white chess rook, empty, unicode white chess rook, unicode white chess king, line break. Instead of examining the chess position: say "Fritz Saemisch - Aron Nimzowitsch, Copenhagen 1923: the Immortal Zugzwang Game. Nimzowitsch (black), observing that white will very soon have to play a terrible move, has just advanced his h pawn for no reason other than to wait. So it is white to play..."; say "[fixed letter spacing]......k. [line break]...q..p. [line break]p..bp..p [line break]...p.r.. [line break].p.Pp... [line break]...bQ.PP [line break]PP.B.rB. [line break].N..R.RK [variable letter spacing][line break]"; say "'White must, willy-nilly, eventually throw himself upon the sword', in Nimzowitsch's commentary. "; say "We will now try to display the same position using chess-piece symbols in a Unicode font."; say fixed letter spacing; now the empty square text is " "; display the board; say variable letter spacing. The Astrological Observatory is above Alphabet Soup. The planets are in the Observatory. "Diagrams of the planets are scattered across the dome: Sun [unicode Sun], Mercury [unicode Mercury], Venus [unicode Female Sign], Earth [unicode Earth], Moon [unicode First Quarter Moon] and [unicode Last Quarter Moon], Mars [unicode Male Sign], Jupiter [unicode Jupiter], Saturn [unicode Saturn], Uranus [unicode Uranus], Neptune [unicode Neptune], Pluto [unicode Pluto] and one or two comets [unicode Comet]. Fainter, but all around, you see stars black [unicode black star] and white [unicode white star]." The constellations are in the Observatory. "Ringing the dome are the constellations: Aries [unicode Aries], Taurus [unicode Taurus], Gemini [unicode Gemini], Cancer [unicode Cancer], Leo [unicode Leo], Virgo [unicode Virgo], Libra [unicode Libra], Scorpius [unicode Scorpius], Sagittarius [unicode Sagittarius], Capricorn [unicode Capricorn], Aquarius [unicode Aquarius], Pisces [unicode Pisces]." The weather almanac is in the Observatory. The description of the almanac is "Here nightly observers scrawl in hasty abbreviations for the current weather conditions: clear weather [unicode Black Sun with Rays], cloudy [unicode cloud], rain [unicode umbrella], snow [unicode snowman], lightning [unicode lightning], thunderstorm [unicode thunderstorm]." The Danger Zone is below Alphabet Soup. The printed name of the Danger Zone is "[unicode skull and crossbones] Danger Zone [unicode skull and crossbones]". The warning signs are in the Danger Zone. "A variety of international-standard warning standards suggest that this may not be the safest place: [unicode skull and crossbones], [unicode caution sign], [unicode radioactive sign], [unicode biohazard sign]." This example text was used to produce a story file which has been tried against both Zoom for Mac OS X and Windows Frotz. The Latin, Greek, Cyrillic and Hebrew text all functioned perfectly on both, but a point of difference showed when writing the Hebrew alphabet: Zoom wrote this right-to-left, Windows Frotz left-to-right. The exotic symbols displayed on Zoom (though others not mentioned above, such as "[unicode staff of hermes]", did not): but most appeared only as black squares on Windows Frotz, exceptions being the astrological signs for Venus and Mars and the musical note. Example 71 (*): Fifty Ways to Leave Your Larva Using text substitution to make characters reply differently under the same circumstances. We can use these substitutions to put together fairly complicated variations within a single piece of text: "Fifty Ways to Leave Your Larva" The Beekeeper's Palace is a room. Wasp is a woman in the palace. Drone is a man in the palace. Instead of kissing someone: say "'[denial], [insult]! [boast]!'"; In this context, [denial] is understood to refer to the denial property of the noun -- but we could spell it out with "denial of the noun" if we wanted to. A person has some text called denial. The denial of a person is usually "Stand back". The denial of Drone is "You forget yourself" A person has some text called insult. The insult of a person is usually "Grasshopper". The insult of Wasp is "Larva". A person has some text called boast. The boast of a person is usually "I am ferocious". The boast of Drone is "I have ferocious allies". And then it would be trivial to insert further rules using these responses: Instead of attacking someone: say "'Get away, [insult]!'" Test me with "kiss wasp / hit wasp / hit drone / kiss drone". Example 72 (***): Fifty Times Fifty Ways Writing your own rules for how to carry out substitutions. There is only so much we can cram into a text property, so being able to swap in properties is useful but limited. Fortunately, we can also, if we want, create new phrases for how to say things in brackets: "Fifty Times Fifty Ways" The Beekeeper's Palace is a room. Wasp is a woman in the palace. Drone is a man in the palace. A person can be fierce or mellow. Wasp is fierce. Drone is mellow. A person can be calm or angry. A person is usually calm. A person has some text called insult. The insult of a person is usually "Grasshopper". The insult of Wasp is "Larva". Instead of kissing someone: say "'[denial for the noun], [insult for the noun]! [boast]!'"; Now to provide some meaning to these bracketed forms. We'll start with the easy one: To say boast: say "I have ferocious allies". This is a "to say" phrase; we will learn more about phrases in a later chapter, but for now it may be enough to observe that whatever we write after "to say..." becomes a valid substitution in bracketed speech. In this particular case there is no advantage to using the boast token rather than spelling the text out in the quotation, but we might in theory add further instructions to randomize the output, for instance. To say phrases can be more complex, as well, since we can have them incorporate extra information: To say insult for (speaker - a person): if speaker is angry, say "[the insult of the noun]"; otherwise say "small one". Here where we have (speaker - a person), we are leaving a slot which we can later fill in, madlibs-like, with any person we like. That is why we can write "insult for the noun": we are summoning the To say phrase and telling it to fill in the identity of the unknown speaker with the noun. This differs from "insult of the noun" in the previous example; in that case, each person had his own insult property, and were merely printing that property out. Here we are actually telling Inform to calculate anew what the insult should be, and giving it some instructions about how to do that. Our instructions can also get arbitrarily complex: To say denial for (speaker - a person): if speaker is calm: say "You must not"; otherwise if speaker is female: say "Stand back"; otherwise: say "You forget yourself". Instead of attacking someone: now the noun is angry; say "'Get away, [insult]!'" Test me with "kiss wasp / hit wasp / kiss wasp / kiss drone / hit drone / kiss drone". So the effects we can get with text substitutions are quite flexible. We could even, if we wanted, fill in the substitutions by random choice, or by selecting items from a long list or table, should we have so bellicose a set of characters that they cannot make do with one or two insulting remarks apiece. Example 73 (*): Finishing School The "another" adjective for rules such as "in the presence of another person". It is often useful to write action rules which apply only when the player is observed by a third party. "In the presence of a person", however, will react even if only the player is in the room, because the player is, of course, a person as well. A convenient way around this problem is to define an "other" adjective: "Finishing School" The apple is an edible thing carried by the player. The Hall is a room. Miss Wicket is a woman in the Hall. The Dormitory is south of the Hall. Definition: a person is another if it is not the player. Instead of eating something in the presence of another person: say "Your mannerly upbringing prevents you from eating without a fork or knife in front of someone." Test me with "eat apple / south / eat apple". If we did not have "another" here, Inform would interpret even the player as a possible schoolmarm, leading to such lines as "yourself stares at you coldly...". Clearly not quite the thing. Example 74 (***): Only You... Smoke which spreads through the rooms of the map, but only every other turn. Suppose we want to have smoke that spreads from room to room, gradually filling the entire map with a clogging smoke. Having it spread every single turn would make for a pretty rapid diffusion, so we temper this by having it spread only on even-numbered turns, instead. Conveniently, Inform by default already knows about even and odd numbers, so we can write: "Only You..." Section 1 - The Procedure Every turn when the turn count is even: if every room is smoky, make no decision; if location is unsmoky, let current state be 0; otherwise let current state be 1; repeat with area running through smoky rooms: now every room which is adjacent to the area is smoky; if current state is 0 and the location is smoky, say "[The location] is filling rapidly with smoke." A room can be smoky or unsmoky. Some air is a backdrop. Air is everywhere. Instead of doing something other than examining or smelling to air: say "It's just air." Understand "smoke" as the air when the location is smoky. Instead of examining the air in a smoky room: say "A thick layer of smoke lies just under the ceiling." Instead of smelling the air in a smoky room: say "Agh, acrid." Instead of smelling a smoky room: try smelling the air. After looking in a smoky room: say "A thick layer of smoke has gathered under the ceiling." Section 2 - The Scenario The Guide Lodge is a room. "A very spacious room capable of containing several hundred girls while they eat, talk, or do crafts. It is constructed in a not-unappealing rustic style, with floor-to-ceiling windows overlooking the lake below, and a fieldstone hearth at the center." The Guide Lodge is smoky. The Kitchen is north of the Guide Lodge. "Multiple eight-burner ranges, ovens, and a walk-in refrigerator: you know the sort of thing." The Industrial Pantry is east of the Kitchen. "Awe-inspiring quantities of food line every shelf, from the three-gallon tub of mayonnaise to the 50-pound tub of rice. Perhaps the most astonishing item is a bag of marshmallows big enough to double as a futon." The player is in the Pantry. The Hallway is west of the Guide Lodge. The description of the Hallway is "A perpetually-crammed hallway which has to handle the overflow line for the toilets." A singed sign is fixed in place in the Hallway. The description of the sign is "Where the edge of the sign has not been burnt, the legible words are '...Can Prevent Forest Fires'." The Toilets are north of the Hallway. "Always in full use, at least when the 12-to-15s are here." The Coat Closet is south of the Hallway. "Muddy boots may not be worn inside the lodge; instead, about 250 pair are piled here, along with their owners' damp parkas and umbrellas." The Craft Supply Room is west of the Hallway. "A holding-depot for jugs of white glue and popsicle sticks." Test me with "x smoke / z / z / z / z / x smoke / look". Example 75 (**): Versailles A mirror which will reflect some random object in the room. One of the advantages of descriptions is that we can use them to pick an item randomly from a specified category. (For more on this possibility, see the Change chapter sections on randomness.) For instance, suppose we wanted to create a mirror in which the player would see some item from the room reflected. We might write Instead of searching the mirror: say "You see [a random thing in the location] reflected back at you." This is the same as "a random thing which is in the location": phrase "in..." can be used briefly in Inform as it can in English. But, on a little more thought, we might want to expand on this: the mirror perhaps should reflect not only things that are in the room, but anything that the player can see (even if it's on a supporter or carried by someone). So then we might instead write Instead of searching the mirror: say "You see [a random visible thing] reflected back at you." There's still a risk, though, that this will produce the response You see the mirror reflected back at you. because, of course, the mirror is itself visible. So instead we might write Instead of searching the mirror: say "You see [a random visible thing which is not the mirror] reflected back at you." "Versailles" The Hall of Plywood Boards is a room. "The Hall of Mirrors is under reconstruction: it is currently a dank tunnel enlivened only by short placards about the history of the room. As though to mock tourists such as yourself who bought their tickets without knowing this, the officials have left uncovered a single panel of mirror." The mirror is scenery in the Hall of Plywood Boards. Understand "panel" or "panel of mirror" as the mirror. The description is "Lovingly restored to shimmering brilliance, it suggests how marvelous this room would be if you had had the good sense to arrive after the renovations were complete." Some tourists are a person in the Hall of Plywood Boards. The tourists are scenery. Instead of searching the mirror: say "You see [a random visible thing which is not the mirror] reflected back at you." Test me with "x mirror / look in mirror / g". A final note: we use "searching" here because Inform understands both SEARCH THING and LOOK IN THING as the searching action, and the player is most likely to type LOOK IN MIRROR in order to see the reflection there. In the absence of an example, we can discover the relationship between actions and their command vocabulary in one of two ways. A complete list of actions and the vocabulary associated with them is available in the Actions index. Alternatively, we can type ACTIONS at a prompt, followed by LOOK IN MIRROR, and get the response [searching the mirror] You find nothing of interest. [searching the mirror - failed the can't search unless container or supporter rule] ...which tells us that Inform is understanding the action as "searching the mirror". Example 76 (***): Lean and Hungry A thief who will identify and take any valuable thing lying around that he is able to touch. "Lean and Hungry" Substance is a kind of value. The substances are silver, gold, and lead. Everything has a substance. A thing is usually lead. Definition: a thing is valuable if it is not lead. The Limestone Cave is a room. "Not very big, and it doesn't go back far, but you'd hoped to find some shelter here. Outside it is raining exceptionally hard." The sinister gentleman is a man in the Cave. "Leaning against the wall is a sinister gentleman in a threadbare waistcoat." The description is "He looks as though he might once have been quite well off." After examining the gentleman: say "[The noun] smiles back at you in an unnerving fashion." Now we make the rule that governs the gentleman's behavior. Here we're going to invoke the rules that allow characters besides the player to do actions. More about this can be found in the Advanced Actions chapter: Every turn: if the sinister gentleman can touch something valuable (called the treasure) which is not carried by a person: try the gentleman taking the treasure. Report the gentleman taking something: say "[The gentleman] slyly acquires [the noun] and tucks it into his pocket." instead. That "not carried by a person" prevents the gentleman from stealing from the player (or, less plausibly, from himself). If we did want him to pick pockets, we could just have said "which is not carried by the gentleman". The player is carrying a coin, a bust of Abraham Lincoln, a bottle of sherry, a small pistol, and a wad of Confederate cash. The coin is gold. The pistol is silver. A locket is in the Cave. The locket is gold. "A broken gold locket lies on the ground, a token of your late Mama." Test me with "get locket / i / drop locket / z / drop cash / z / x gentleman / drop all / z / z / look". Example 77 (*): Mistress of Animals A person who moves randomly between rooms of the map. Suppose we want a restless sort of character always pacing from room to room. It is quite easy to use adjacency to achieve this effect: "Mistress of Animals" Corinth is a room. Athens is east of Corinth. Epidaurus is southeast of Corinth and east of Mycenae. Mycenae is south of Corinth. Olympia is west of Mycenae. Argos is south of Mycenae. Thebes is northwest of Athens. Pylos is south of Olympia. Sparta is east of Pylos and south of Argos. Delphi is northwest of Thebes. Artemis is a woman in Thebes. Every turn: if Artemis is in a room (called the current space): let next space be a random room which is adjacent to the current space; if Artemis is visible, say "Artemis heads to [the next space]."; move Artemis to next space; if Artemis is visible, say "Artemis arrives from [the current space]." Test me with "z / z / z / z / z / z". Of course, it helps that Artemis is the sort to like open spaces. The implementation would become more complicated if there were doors which might block transit between these locations. Example 78 (*): All Roads Lead to Mars Layout where the player is allowed to wander any direction he likes, and the map will arrange itself in order so that he finds the correct "next" location. Suppose we want to allow the player to wander freely in any direction, but ourselves maintain control over the order in which he encounters the rooms. This sort of effect emphasizes the order of the story-telling over any kind of rigorous simulation of space; on multiple play-throughs, the player might not find all the same rooms in the same locations. "All Roads Lead to Mars" Before going a direction (called way) when a room (called next location) is not visited: let further place be the room the way from the location; if further place is a room, continue the action; change the way exit of the location to the next location; let reverse be the opposite of the way; change the reverse exit of the next location to the location. The Open Plain is a room. "A wide-open grassy expanse, from which you could really go any way at all." The Hilly Place is a room. "The grassland gives way to a somewhat more hilly area, though there is still very little to guide you any particular way." The Stream is a room. "This is the third place you've been today, and so the stream is welcome. How refreshing!" Test me with "n / s / e / e". If we wanted still to be able to find routes between places, we could define a relationship of connection between rooms, which we would add to as we went along. Example 79 (**): Hotel Stechelberg Signposts such as those provided on hiking paths in the Swiss Alps, which show the correct direction and hiking time to all other locations. The following rule appends a paragraph to every room description. We need not worry about doors (despite the pass in the Bernese Oberland known figuratively as the "Little Door"). "Hotel Stechelberg" After looking: say "Yellow arms on the signpost point:-[line break]"; repeat with destination running through interesting rooms: let the way be the best route from the location to the destination; if the way is a direction, say " [way] for [the destination]: [number of moves from the location to the destination] Std." Hotel Stechelberg is a room. "The wooden hiking inn at the end of the road, with flowerboxes, canton flags, outdoor tables and a triangular paddock for the cows contesting the annual Miss Stechelberg competition. Otto and Marianne do cheerful innkeeper things, while the sun blazes from a gentian-blue sky." A room can be dull or interesting. A room is usually dull. North of Hotel Stechelberg is Trummelbachfalle. North of Trummelbachfalle is Lauterbrunnen. Lauterbrunnen is interesting. Southeast of Hotel Stechelberg is Trachsellauenen. Trachsellauenen is interesting. Test me with "look". With a bit more work, the result might be: Hotel Stechelberg The wooden hiking inn at the end of the road, with flowerboxes, canton flags, outdoor tables and a triangular paddock for the cows contesting the annual Miss Stechelberg competition. Otto and Marianne do cheerful innkeeper things, while the sun blazes from a gentian-blue sky. Yellow arms on the signpost point:- north for Lauterbrunnen: 2 Std. west for Sefinental: 2 Std. west for Schilthorn: 6 Std. southeast for Trachsellauenen: 1 Std. southeast for Oberhornsee: 3 Std. Example 80 (***): A View of Green Hills A LOOK [direction] command which allows the player to see descriptions of the nearby landscape. Suppose a game in which the player is wandering an open landscape with long vistas, allowing him to LOOK in some direction, or even look at an adjacent location. "A View of Green Hills" Corinth is a room. Athens is east of Corinth. Epidaurus is southeast of Corinth and east of Mycenae. Mycenae is south of Corinth. Olympia is west of Mycenae. Argos is south of Mycenae. Thebes is northwest of Athens. Pylos is south of Olympia. Sparta is east of Pylos and south of Argos. Delphi is northwest of Thebes. Understand "look [direction]" as facing. Facing is an action applying to one visible thing. Carry out facing: let the viewed item be the room noun from the location; if the viewed item is not a room, say "You can't see anything promising that way." instead; try looking toward the viewed item. In rules about action handling, "noun" refers to the first object that the player has mentioned in his command, so if the player typed >LOOK WEST, "let the viewed item be the room noun from the location" would be processed as "let the viewed item be the room west from the location", and so on. We can at need override the default behavior, if it is not going to be appropriate for the player to see the next room over. There is only sky above at any time, so... Instead of facing up: say "Above you is bright sky." Understand "look toward [any adjacent room]" as looking toward. Understand "examine [any adjacent room]" as looking toward. Looking toward is an action applying to one visible thing. Carry out looking toward: say "You make out [the noun] that way." This design allows us to create descriptions for rooms (as seen from the outside) which will work regardless of where we're looking from. For instance: Instead of looking toward Athens: say "Even from here you can make out the silhouette of the Acropolis." Test me with "look north / look south / look up / look east / east / look west". Example 81 (***): Unblinking Finding a best route through light-filled rooms only, leaving aside any that might be dark. Suppose we're simulating a situation where the player needs to travel through lit areas only, but we want to give him some hints about which way might be safe. Here we'll find our best route through light-filled rooms. The slightly tricky part is that it's not necessarily easy to tell whether a room has a lamp in it. We may say "if the Crypt is lighted", but that only tells us whether it has been declared to be inherently lighted or dark, not whether it happens to contain a light source that the player would be able to see if he went in. The easiest way to get around this is to create an object -- the light-meter; place it in the target location; and check whether it "can see" a lit object. This preserves all the usual rules about open and closed containers, transparency, etc. "Unblinking" Section 1 - Procedure The light-meter is a privately-named scenery thing. Definition: a room (called the target room) is light-filled: if the target room is lighted: yes; move the light-meter to the target room; if the light-meter can see a lit thing: yes; remove the light-meter from play; no. That done, we're free to use our best-route phrases to choose a particular route. Section 2 - Scenario The Tomb of Angels is a room. "This ancient underground tomb is lightless but for a few shafts from the surface. Everywhere in the shadows are carved angels, their faces worn away by water and pollution, their wings little more than nubs." The Upward Path is above the Tomb of Angels. It is dark. "The staircase switches back on itself many times as it ascends towards the Crash Site." A container called the sarcophagus is in the Upward Path. It is closed and openable. "A sarcophagus rests in the niche here, [if open]the lid pushed aside[otherwise]the lid firmly in place[end if]." The Crash Site is above the Upward Path. "The ceiling has wholly caved in here, and the belly of the spaceship above you is visible -- including the escape hatch." A candle is a kind of thing. A candle is usually lit. The player carries four candles. After looking when the location is not the Crash Site: if the best route from the location to the Crash Site through light-filled rooms is a direction (called next way): say "It looks like there's a safe, lit path [if the number of moves from the location to the Crash Site through light-filled rooms is 1]straight[otherwise]if you go[end if] [next way]."; otherwise: say "It looks like there is no fully lit path from here to the Crash Site." Test me with "up / drop candle / down / up / take the candle / open sarcophagus / put candle in sarcophagus / down / up / close sarcophagus / d". An important word of caution: this method would give false negatives if there were a backdrop lightsource, such as the moon, providing light to the Upward Path. This is because backdrops are actually moved around the map by Inform during play, following the player around. So if the moon backdrop is in the Crash Site with the player, it will not be in the Upward Path as well -- even if it's scheduled to move there as soon as the player does. Example 82 (****): Revenge of the Fussy Table A small game about resentful furniture and inconvenient objects. This example does include a number of features that we haven't met yet, particularly rulebooks. Nonetheless, the basic idea should be relatively clear. Our premise is that the player is faced with a series of disgruntled furnishings, none of which want to be responsible for supporting the cold, hot, drippy, or spiky objects lying around the room. "Revenge of the Fussy Table" Section 1 - The Supporters The Dining Room is a room. "A room of handsome proportions, with an octagonal dining table on a fine parquet floor. The original set of chairs has been taken away, leaving only a red velvet dining chair and a blue suede armchair." The fussy table is a supporter in the Dining Room. It is scenery. The description is "It's hypochondriac: the result of a sojourn in a superior antique shop, where it picked up the scent of almond oil, words like provenance, and a secretive shame about being resurfaced. Chairs don't get along with it. In its mellowest moods, after a really good dusting, it will mention, casually, a cabinet it once knew, which was twelve feet tall, came from the Winter Palace, and had an asking price of $350K." A chair is a kind of supporter with carrying capacity 1. A chair is enterable. A chair is usually scenery. Understand "chair" as a chair. The blue suede armchair and the red velvet dining chair are chairs in the Dining Room. The description of the blue suede is "Quiet, mellow, and with a lingering aroma of clove cigarettes, and possibly something less legal. It doesn't sit up straight, and doesn't let anyone else do so either." The red velvet has the description "In temperament, in bearing, in everything it is the opposite of the blue suede chair. It is concerned for its duty all the time, has a rigidly straight back, and pokes diners in the spine when it suspects them of overdoing things." The carrying capacity of the player is 2. Section 2 - Sources of Unpleasantness A thing can be drippy or dry. Heat is a kind of value. The heats are luke-warm, cold, and scalding. Everything has a heat. Understand the heat property as describing a thing. A thing can be spiky or smooth. The cleated left shoe is a wearable spiky thing. It is worn by the player. The cleated right shoe is a wearable spiky thing. It is worn. Definition: a thing is unpleasant if it is scalding or it is cold or it is spiky or it is drippy. Definition: a supporter is occupied if something is on it. Definition: something is contented if it is not concerned. Definition: a chair is concerned if something unpleasant is on it. Definition: the table is concerned if something drippy is on it or something scalding is on it or something spiky is on it. Definition: the ceramic tile is concerned if something spiky is on it. Definition: a room is concerned if something drippy is in it or something scalding is in it or something spiky is in it or someone which is in it is wearing a spiky thing. Before printing the name of a drippy thing: say "drippy ". Before printing the name of a cold thing: say "cold ". Before printing the name of a scalding thing: say "scalding ". Section 3 - What the Player Can Do About It After putting a cold thing on a scalding thing: say "[The noun] meets [the second noun]; both shriek in pain. But the necessary heat transfer occurs."; now the heat of the noun is luke-warm; now the heat of the second noun is luke-warm. After putting a scalding thing on a cold thing: say "[The noun] meets [the second noun]; both shriek in pain. But the necessary heat transfer occurs."; now the heat of the noun is luke-warm; now the heat of the second noun is luke-warm. After taking a scalding thing: say "'Right,' you say. 'I'll just hold onto [the noun], shall I? Because that won't be in the least uncomfortable for me.'" After taking a drippy thing: say "With a sense of martyrdom, you retrieve [the noun], which dribbles water down your cuffs." After entering a chair when the player is wearing a spiky thing (called the clog): say "You sit on [the noun], lifting [the list of spiky things worn by the player] so that the parquet is no longer affronted." Section 4 - In Which the Furnishings Complain An every turn rule: follow the complaint rules. The complaint rules is a rulebook. A complaint rule: if something (called the offending item) on the table is drippy: say "'Help! Get me a coaster!' screams the table[if the table is visible], its veneer squirming under [the offending item][otherwise] from the Dining Room[end if]."; rule succeeds; if something (called the offending item) on the red chair is drippy: say "'Oh dear,' murmurs the red chair, as [the offending item] drips into its velvety seat. 'Oh dear, I will have a damp spot. This is so very -- what will people think?'"; rule succeeds; if something (called the offending item) on the visible armchair is drippy: say "[The offending item] visibly begins degrading the suede where it sits. The armchair is tactfully silent."; rule succeeds; if a drippy thing (called the offending item) is in the location and the player is in the Dining Room: say "'Cripes,' says the parquet. 'No one mind me at all. Just leave that [offending item] right here. You know I'm the most valuable thing in the room?'"; rule succeeds. A complaint rule: if a cold dry thing (called the offending item) is on the table: say "The table shivers under [the offending item]."; rule succeeds. A complaint rule: if something (called the offending item) on the table is scalding: say "'Hey!' protests the table, practically smoking at [the offending item]. 'Heard of a trivet?'"; rule succeeds; if something (called the offending item) on the armchair is scalding: say "The armchair doesn't complain about [the offending item]; it just begins, quietly, to give off warm sweet clouds of blue steam, as though its inner opium-nature had been released."; rule succeeds; if something (called the offending item) in the Dining Room is scalding: say "'Yes indeed,' [if the location is the Dining Room]says[otherwise]bellows[end if] the parquet. 'That [offending item] won't leave any sort of mark what-so-ever.'"; rule succeeds. A complaint rule: if something (called the offending item) on the table is spiky: say "The table holds very very very still lest [the offending item] mar its finish. But its resentment is palpable."; rule succeeds; if something (called the offending item) on the velvet chair is spiky: say "[The offending item] stabs the velvet of the red velvet chair, which draws itself up even more sharply in a pose of dutiful martyrdom."; rule succeeds; if something (called the offending item) which is spiky is on the ceramic tile: say "'[The offending item] itches!' cries the ceramic tile."; rule succeeds; if something (called the offending item) in the location is spiky: say "'[The offending item] should not be on a parquet floor,' sings the parquet floor sadly."; rule succeeds; if someone (called the offending person) in the location is wearing something spiky and the location is the Dining Room: say "The parquet floor mutters about the things people wear to walk on parquet floors these days."; rule succeeds. A complaint rule: if the table supports something which supports a drippy thing (called the offending item), say "'[The offending item] could still theoretically dribble down here,' says the table nonchalantly. 'It's possible.'"; if the velvet chair supports a concerned thing (called the friend), say "'[The friend] seems a little worried,' remarks the velvet chair helpfully." A complaint rule: if the concerned table can see a supporter (called the object of envy) which is not concerned: say "The table looks jealously at [the object of envy]. 'Some people have such an easy life.'"; rule succeeds. Instead of going to an adjacent room when the player is in the Dining Room: say "'You're not leaving!?' whimpers the table at once." Moreover, every time the player gets close to resolving this issue, his unhelpful companion Alison brings in something else inconvenient. We can use the counting of contented supporters to decide when the player is getting close to winning and it's time for her to bring something else... Section 5 - Source of Further Complications The Tidy Kitchen is south of the Dining Room. Alison is a woman in the Tidy Kitchen. The kettle is a scalding thing. The ceramic tile is a cold portable supporter. It has carrying capacity 1. The platter is a scalding portable supporter. It has carrying capacity 1. The glass of ice water is a cold, drippy thing. Instead of drinking the glass of ice water, say "It's not yours, it's for Alison, once she finishes cooking." Alison carries the kettle, the tile, the platter, and the glass. An every turn rule: follow the behavior rules. The behavior rules is a rulebook. A behavior rule: if ice water is carried by Alison and the player is in the Dining Room and almost all of the supporters are not concerned: let the next victim be a random fixed in place contented supporter; move the ice water to the next victim; say "Humming to herself, Alison brings in [an ice water] and sets it down smack on [the next victim], then goes back out."; rule succeeds. A behavior rule: if platter is carried by Alison and the player is in the Dining Room and almost all of the supporters are not concerned: let the next victim be the red velvet chair; move the platter to the next victim; say "Whistling a jaunty tune, Alison brings in a hot platter and deposits it on [the next victim], then returns to the kitchen."; rule succeeds. A behavior rule: if the tile is carried by Alison and the player is in the Dining Room and almost all of the supporters are not concerned: let the next victim be a random contented chair; move the tile to the next victim; say "Humming to herself, Alison brings in [the tile] and sets it down smack on [the next victim], then goes back out."; rule succeeds. A behavior rule: if kettle is carried by Alison and the player is in the Dining Room and at least three fixed in place supporters are contented: let the next victim be the fussy table; move the kettle to the next victim; say "Just then the kettle boils in the kitchen. Whistling chirpily, Alison brings it in and sets it down smack on [the next victim], then goes back out."; rule succeeds. And just so that the player knows where he stands at the end of each turn: Section 6 - General Assessment An every turn rule: if some of the things are concerned, say "You sense some resentment from [the list of concerned things]." An every turn rule: if the player is carrying more than one scalding thing: let the dropped item be a random scalding thing carried by the player; say "You can't hang onto so many burning hot things, and lose your grip on [the dropped item].[line break]"; silently try dropping the dropped item. An every turn rule: if almost all of the supporters are concerned, say "'I hope everything is going well,' bellows Alison from the other room." Finally, we need some rules to decide when the player is, in fact, finished. Section 7 - Scoring An every turn rule: now score is 5 minus the number of concerned things; if the location is concerned, decrement the score; if all of the supporters are concerned and the location is concerned, end the story; if none of the supporters are concerned and the location is not concerned, end the story finally. The maximum score is 5. When play begins, now score is 4. Test me with "i / take off left shoe / get the glass / put the glass on the platter / get the tile / drop the tile / get the kettle / put the kettle on tile / sit on the blue armchair". Example 83 (**): Yolk of Gold Set of drawers where the item the player seeks is always in the last drawer he opens, regardless of the order of opening. Suppose that for dramatic effect we would like the player to find the thing he is looking for always in the last drawer he opens... "Yolk of Gold" The Turret is a room. "A cramped little room distinguished chiefly by the spiral staircase that descends from it. The windows look out over the rooftop." The Rooftop is outside from the Turret. The staircase is an open unopenable door. It is scenery. It is below the Turret and above the Library. The description is "A winding stair carved out of the single trunk of a massive tree, all in a dark wood; the outside of the stairs left unfinished with the bark still on, but the treads worn smooth by long and constant use." The description of the Library is "Here, it seems, you have found your mark: books line both walls, a dark carpet lies on the floor, and a strange dress hangs up in a presentation case. And the thing you were told to look for, a desk with three drawers. A spiral staircase leads up and out." The cherry desk is scenery in the library. The description is "A deep, satin-lustrous cherry, with scrollwork legs and gilt touches. The years have not been kind, and it has cracked and split in several places; the finish is damaged, and where there is inlaid mother of pearl, it is beginning to come up from its bed. But it is still a sound piece, and features three drawers." After examining the desk for the first time, say "(Your employers were able to tell you to look for it, but not which drawer to look in. Typical.)" A drawer is a kind of container. A drawer is always openable and closed. The description of a drawer is "The usual drawer of heavy wood, inadequately smoothed for ease of use." The top drawer is a drawer. The middle drawer is a drawer. The bottom drawer is a drawer. The top drawer, the middle drawer, and the bottom drawer are part of the desk. A drawer can be explored or unexplored. A drawer is usually unexplored. Instead of searching a closed drawer, try opening the noun. After opening a drawer when no drawers are explored: now the noun is explored; say "There is a tremendous screech, but nothing whatsoever inside, not even dust." After opening an unexplored drawer when exactly one drawer is explored: now the noun is explored; say "You struggle to open this one a bit more quietly, conscious all the time of noise... but no, it's empty. Just stands to reason." After closing a drawer: say "There is a racket of wood protesting against wood as you do so, which makes you wonder if you hadn't better just leave them open from now on. The unhappy owner is probably going to catch on soon enough anyway." Before opening an unexplored drawer when exactly two drawers are explored: move the mysterious thing to the noun; now the noun is explored. There is a mysterious thing. The description is "A very familiar-looking hemispherical weight of metal, goldish in tone though perhaps not made of gold. This one has a slight stickiness about the bottom surface." Instead of opening the desk when at least one drawer is unexplored: let the next drawer be a random unexplored drawer; say "(starting with [the next drawer])[line break]"; try opening the next drawer. Instead of looking under the desk when no drawers are explored: say "You carefully survey the ground around the desk. There don't seem to be any hidden tripwires or traps to prevent you from having a look in the drawers." Instead of looking under the desk when at least one drawer is unexplored: say "Nothing there either. Thoroughness is a virtue with tedium as a side effect, as your mother used to say -- but they always counted her a trifle slapdash." Instead of looking under the desk when all drawers are explored: say "There's nothing down there, but this doesn't come as a great surprise." Instead of searching the desk when at least one drawer is unexplored: move the mysterious thing to the player; say "You perform a hasty, squeaky search of "; if no drawer is explored, say "all three drawers, discovering nothing and nothing in rapid succession. But on the third drawer you "; if exactly two drawers are unexplored, say "the remaining two drawers. There's nothing in the second, but in the third you "; if exactly one drawer is unexplored, say "the last drawer. In it, you "; say "turn up a promising hemispherical object."; now all the drawers are explored. Perhaps, just for fun, we have all the other scenery draw the player's attention back to the main point, as well. The carpet is scenery in the Library. The description is "It is too dark for you to make out details of the antique design, which seems dimly to represent an early voyage to the moon, with ships and the travelling stars." Understand "rug" as carpet. Instead of looking under the carpet: if none of the drawers are explored, say "You peel up a corner of the rug gingerly; nothing results. A perfectly ordinary rug, then." instead; if all of the drawers are explored, say "No time for that kind of nonsense. You'd better get out and away while you can." instead; if some of the drawers are explored, say "No time for that nonsense. The desk's what you want now; what you came for won't be embedded in the flooring." instead. The glass presentation case is transparent scenery in the Library. The description is "The case is taller than you are, framed in wood, with large panels of glass, the better to display the remarkable contents." Instead of attacking the glass presentation case: say "The glass pane of the presentation case shatters, throwing fine glass everywhere, including over the delicate museum-piece inside. Nor does the noise pass unnoted: only a second passes before there are footsteps in the hall, and though you make for the concealing darkness and escape of the turret, you are not swift enough. The servants are soon on you, and you are made to regret, quite painfully, this casual act of vandalism."; end the story saying "You have lost your opportunity." The strange dress is a wearable thing in the glass case. The description is "Not the sort of dress that anyone wears now: such elaboration would be ludicrous. It drips gold -- gilt lace, ruffles of trimmed gold, shimmering golden tracery -- dulled here and there by the sinister black of faceted jet." Test me with "d / x case / x dress / x carpet / look under carpet / look under desk / x desk / open top drawer / close top drawer / look under desk / open bottom drawer / close bottom drawer / open middle drawer / get thing / look under carpet / look under desk / up". Example 84 (*): Grilling A grill, from which the player is not allowed to take anything lest he burn himself. Descriptions of objects can be used in "Instead" rules: we can not only say "Instead of taking the steak", but also "Instead of taking something" or "Instead of taking something which is on the grill". That last rule is useful if, for example, we want to prevent the player from interacting with anything on a specific supporter: "Grilling" The Patio is a room. The Patio contains a grill and an ice chest. The ice chest contains a cold beer. On the grill are a steak and a hot dog. Mom is a woman in the Patio. Instead of taking something which is on the grill: say "'Hey, you'll burn yourself,' says Mom." Test me with "get steak / get all from grill / get all". We could just as easily adapt this rule to affect a container: "Instead of taking something which is in the ice chest," for example. Note also that in older versions of Inform, the pattern "get all from..." was treated differently from "get steak", and had to be accounted for separately. This is no longer the case; this instead of taking... rule will handle all the phrasings which the player might use to try to acquire this object. Example 85 (*): Bad Hair Day Change the player's appearance in response to EXAMINE ME. "Bad Hair Day" The Foyer is a room. "A mirror hangs over the table, tempting you to check your appearance before going in with all the others." Instead of examining the player: say "Oh, stop fussing. You look fine." Test me with "examine me". Example 86 (***): Democratic Process Make PUT and INSERT commands automatically take objects if the player is not holding them. "Stop" and "Continue" are most useful when we need to write rules that will have to stop the action some of the time but at other times let it pass; so for instance: "Democratic Process" Before inserting something which is not carried by the player into something: if the noun is in the second noun, say "Already done." instead; say "(first taking [the noun])[line break]"; silently try taking the noun; if the player is not holding the noun, stop the action. Before putting something which is not carried by the player on something: if the noun is on the second noun, say "Already done." instead; say "(first taking [the noun])[line break]"; silently try taking the noun; if the player is not holding the noun, stop the action. The Assembly Room is a room. "On most days, this room is used for elementary school assemblies; at the moment, it serves as a voting place." The ballot is on the desk. The desk is in the Assembly Room. The machine is a container in the Assembly Room. "On the ballot machine is a sign which reads 'PUT BALLOTS IN ME :)'." Understand "ballot machine" as the machine. Test me with "put ballot in machine". Example 87 (****): Sand Extend PUT and INSERT handling to cases where multiple objects are intended at once. The above example does not quite work when we want the player to be allowed to take multiple objects at once before putting them somewhere: we also need to add a couple of "understand" rules borrowed from many chapters later. While the reasons may not be immediately clear, we include the demonstration here for the sake of thoroughness: "Sand" Before inserting something which is not carried by the player into something: if the noun is in the second noun, say "Already done." instead; say "(first taking [the noun]) "; silently try taking the noun; if the player is not holding the noun, stop the action. Before putting something which is not carried by the player on something: if the noun is on the second noun, say "Already done." instead; say "(first taking [the noun])[line break]"; silently try taking the noun; if the player is not holding the noun, stop the action. Understand "put [things] in [something]" as inserting it into. Understand "put [things] on [something]" as putting it on. The Closet is a room. A lentil is a kind of thing. A black-eyed pea is a kind of thing. The closet contains 3 lentils. The Closet contains 14 black-eyed peas. The round tin is a container in the closet. The round tin contains 17 lentils. The square tin is a container in the Closet. The square tin contains 20 black-eyed peas. Sorting is a scene. Sorting begins when play begins. Sorting ends when all the lentils are in the round tin and all the black-eyed peas are in the square tin. When Sorting ends, end the story finally. When play begins: say "Thanks to your cruel stepmother, you're not going anywhere until the lentils and peas are sorted." Test me with "put peas in square tin / put lentils in round tin". Example 88 (*): Fine Laid Making writing that can be separately examined from the paper on which it appears, but which directs all other actions to the paper. Sometimes it is useful to direct all -- or almost all -- actions from one object to another. For the sake of argument, say we have a sheet of paper with writing on it, and (because we're very meticulous) we want to let the player examine the writing and get a customized response, different from when he just examines the sheet of paper. But for all other purposes -- say, TAKE or TASTE -- we want the two objects to be treated as one. Here, we approach the problem by changing the noun and/or the second noun of the current action, then issuing a new command to "try the current action". Because we've changed the noun and second noun, the "current action" at this point is different from the one generated originally by the player's command. "Fine Laid" High Street Stationer is a room. The sheet of paper is a thing in High Street Stationer. The writing is part of the sheet of paper. The description of the sheet of paper is "A beautiful sheet of heavy cream paper." The description of the writing is "Delicate and spidery." Instead of tasting the sheet of paper, say "You might need more fiber in your diet, but this isn't the way.". Before doing something other than examining when the current action involves the writing: if the writing is the noun, now the noun is the sheet of paper; if the writing is the second noun, now the second noun is the sheet of paper; try the current action instead. Test me with "examine sheet of paper / examine writing / get writing / taste writing". Example 89 (*): Hayseed A refinement of our staircase kind which can be climbed. Presumably all staircase-type connections between rooms should respond when the player says CLIMB STAIRS (or the equivalent). So "Hayseed" A staircase is a kind of door. A staircase is usually open. A staircase is seldom openable. The ladder is a staircase. It is above the Barn and below the Hayloft. Instead of climbing a staircase: try entering the noun. Test me with "climb ladder / g". Attempts to climb other types of door will still be treated as useless. Example 90 (*): Morning After When the player picks something up which he hasn't already examined, the object is described. Suppose we want to make the player's life slightly easier by examining everything he picks up, if he hasn't already examined it. "Morning After" A thing can be examined or unexamined. After taking something unexamined: say "Taken. [run paragraph on]"; try examining the noun. Carry out examining something: now the noun is examined. Carry out rules are explained in more detail in the chapter on advanced action handling. For now, it may be enough to know that what we put into this carry out rule for examining will happen any time anything is examined, but that it will not interfere with the rest of the predefined behavior of the action. The player will still see the object description and so on, as usual. The Red Door Saloon is a room. "This old place is in pretty bad shape since the mine shut down. Now there's not much to see but the pair of deep gouges in the floorboards where they dragged away the Sheriff's corpse with the spurs still on." Jed is a man in the Red Door Saloon. "At 8:30 AM the only person around is old Jed, collecting his hangover cure." The pistol is a thing in the Red Door Saloon. The description of the pistol is "It ain't too accurate, but for two dollars you can't expect much." The hangover cure is a thing in the Red Door Saloon. The description of the hangover cure is "Two yellow egg-yolks unbroken in a red-brown liquid. Yep." Test me with "x pistol / get all". Example 91 (*): Sybil 1 Direct all ASK, TELL, and ANSWER commands to ASK, and accept multiple words for certain cases. Sometimes we do not particularly want to deal with all the variations on asking, telling, or answering someone something, but want to direct everything to a single conversational command: "Consulting the Oracle" The Grove is a room. In the Grove is a woman called the Sybil. Instead of telling someone about something, try asking the noun about it. Instead of answering the noun that something, try asking the noun about it. Instead of asking the Sybil about "persians", say "She nods gravely." And similarly, a difference between GIVE and SHOW is sometimes overkill: Instead of showing something to someone, try giving the noun to the second noun. The player carries a coin. Instead of giving the coin to the Sybil: move the coin to the Sybil; say "She accepts with a smile." It is also often the case that we want to accept more than one form of a term. For instance Instead of asking the Sybil about "Darius/king", say "Her smile unnerves you." will match either "Darius" or "king". If necessary, we can go a step further and define our own token to match a variety of phrases, like this: Understand "Athenians/Spartans/Greeks" or "hoplite army/forces" as "[Greeks]". Instead of asking the Sybil about "[Greeks]", say "She looks encouraging." The token "[Greeks]" will match all of "Athenians", "Spartans", "Greeks", "hoplite army", or "hoplite forces". It will not match "hoplite" or "forces" alone; it is important to note that the / divides individual words which are understood equivalently, but does not define entire phrases as equivalent. More about how Inform understands specific phrases can be found in the chapter on Understanding. Test me with "test one / test two". Test one with "ask sybil about persians / tell sybil about persians / sybil, persians / ask sybil about darius / ask sybil about king". Test two with "ask sybil about greeks / ask sybil about athenians / ask sybil about hoplite army / ask sybil about hoplite forces / give the coin to the sybil". Example 92 (*): Lucy Redirecting a question about one topic to ask about another. Occasionally we will want to replace the player's question topic with another of our own devising. We can do this in the simplest possible case like so: "Lucy" The International Boardgame Championship is a room. Lucy is a woman in the Championship. Instead of asking Lucy about "checkers": try asking Lucy about "games". Instead of asking Lucy about "games", say "'I don't like games,' she sniffs." Test me with "ask lucy about checkers / ask lucy about games". Note that this syntax did not work in older versions of Inform; it is now safe. Example 93 (**): Sybil 2 Making the character understand YES, SAY YES TO CHARACTER, TELL CHARACTER YES, ANSWER YES, and CHARACTER, YES. Inform already understands YES, NO, and SORRY as commands in their own right, which can make things a little sticky when we want a character to ask a question of the player. The most important thing is not to cover some of the possible phrasings while ignoring others. "Replies" The Grove is a room. In the Grove is a woman called the Sybil. Instead of asking the Sybil to try saying no: try saying no. Instead of asking the Sybil to try saying yes: try saying yes. Instead of asking the Sybil to try saying sorry: try saying sorry. Instead of answering the Sybil that "yes", try saying yes. Instead of answering the Sybil that "no", try saying no. Instead of answering the Sybil that "sorry", try saying sorry. Instead of saying yes in the presence of the Sybil: say "She looks interested." Instead of saying no in the presence of the Sybil: say "She looks annoyed." Instead of saying sorry in the presence of the Sybil: say "She looks bored." The complexity arises from the fact that we want to handle both YES and SYBIL, YES. If we only had the latter, 'yes' would be treated as a text given to the Sybil, just as in the commands SAY YES TO SYBIL or ANSWER YES. But because we have defined it as a command (so that the player can use it independently), SYBIL, YES is understood as an order to the Sybil to do the YES action. Fortunately, we can redirect everything, as here, so that the results wind up the same. And if we want yet another variation not covered by the Inform standard: Understand "tell [someone] [text]" as answering it that. Understand "tell [someone] that [text]" as answering it that. But that is a matter for a later chapter. Test me with "yes / sybil, yes / say yes to sybil / answer yes / tell sybil yes / no / sybil, no / say no to sybil / answer no / tell sybil no / sorry / sybil, sorry / say sorry to sybil / answer sorry / tell sybil sorry". Example 94 (***): Costa Rican Ornithology A fully-implemented book, answering questions from a table of data, and responding to failed consultation with a custom message such as "You flip through the Guide to Central American Birds, but find no reference to penguins." The following relies on quite a number of features we haven't met yet: tables, rules for printing names, instructions for understanding the player's commands. It is offered simply as an example of how a fully implemented book might be handled in Inform. "Costa Rican Ornithology" A book is a kind of thing. Understand "book" as a book. A book has a table name called the contents. Instead of consulting a book about a topic listed in the contents of the noun: say "[reply entry][paragraph break]". Report consulting a book about: say "You flip through [the noun], but find no reference to [the topic understood]." instead. With this "topic understood" phrase, we're telling Inform to print back the word or phrase that the player was attempting to look up. This overrides the more general default response, "You discover nothing of interest in the book." We now have the essential elements to construct whatever books we like. Now let's have an example of a specific book: The Guide to Central American Birds is a book carried by the player. The contents of the Guide is the Table of Listed Birds. We will come back to the idea of tables and table names later, but for now the important thing is that we have instructed Inform to look up its answers to consulting the bird guide in this form: Table of Listed Birds topic reply "[red]" or "[red] bird/macaw" "You flip through the Guide for a while and eventually discover a reference to the [scarlet macaw], which appears to correspond with what you see before you." "quetzal/trogon" or "resplendent trogon" "The entry on the quetzal is quite lyrical, describing its brilliant plumage, flashing and igniting in the sunshine, which is supposedly sufficient to lure birdwatchers from all over the world. Unfortunately, the quetzal is described as being bright emerald in color, with a pink fuzz on its head and a long soft tail 'like a feather boa'. None of these describes your visitor." The topic column is a bit special: it matches the player's input, and is not meant to be printed out again. Topic columns will be discussed further in the chapter on Tables. (Note also that, however it may appear in the documentation, the topic column should not be spanning multiple lines in our source text.) We may also compress long or complicated topics by creating bracketed abbreviations, and in fact it's useful to do so now, to explain the red token we just used: Understand "red-orange" or "bird" or "red" or "orange" as the scarlet macaw. Understand "red-orange" or "red" or "orange" or "scarlet" as "[red]". This technique is discussed further in the chapter on Understanding. If we wanted more books, we could define those in the same way, giving each its own separate contents table to be used for consultation. But for the sake of the example we will keep it simple, and move on to the scenario itself: The Veranda is a room. "From here you can see a considerable expanse of dense-growing jungle plants, and eventually the open water beyond." The scarlet macaw is an animal in the veranda. "A vibrantly-colored [scarlet macaw] perches on the rail." A thing can be known or unknown. Before printing the name of the scarlet macaw while consulting: now the scarlet macaw is known. Rule for printing the name of the unknown scarlet macaw: if the macaw is unknown, say "red-orange bird of unknown species". Test me with "look up penguins in the guide / look up quetzal in guide / look up silver nuthatches in the guide / look / look up red bird in the book / look". Example 95 (***): The Art of Noise Things are all assigned their own noise (or silence). Listening to the room in general reports on all the things that are currently audible. This example involves redesigning the LISTEN command, removing its built-in function and replacing that with something more ambitious. We will learn more about how to do this later on. "The Art of Noise" A thing has some text called sound. The sound of a thing is usually "silence". The block listening rule is not listed in the check listening to rules. Carry out listening to something: say "From [the noun] you hear [the sound of the noun]." Instead of listening to a room: if an audible thing can be touched by the player, say "You hear [the list of audible things which can be touched by the player]."; otherwise say "Nothing of note." Definition: a thing is audible if the sound of it is not "silence". Before printing the name of something audible while listening to a room: say "[sound] from the " The Sharper Image is a room. The pet rock is a thing in the Sharper Image. The toy car is a thing in the Sharper Image. The sound of the car is "whirring and zooming". The plastic widget is a thing in the Sharper Image. The sound of the plastic widget is "bleeps and bloops". The pointless gadget is a thing in Sharper Image. The sound of the pointless gadget is "buzzbuzzbuzz". The soundproof case is a transparent openable container in the Sharper Image. It is closed and fixed in place. Test me with "listen / listen to rock / listen to car / get all / open case / put all in case / listen / close case / listen / listen to car". Example 96 (*): Zodiac Several variations on "doing something other than...", demonstrating different degrees of restriction. Notice that the following two scenarios do not have the same effect: "Zodiac" The Secluded Alley is a room. The Capricorn Killer is a man in the Secluded Alley. The player carries a can of mace and a roll of duct tape. Instead of doing something other than examining with the Capricorn Killer: say "You wouldn't dare!" Test me with "x me / x killer / touch killer / smell mace / sing". ...will prevent the player from doing anything else to the killer, but allow him free range of action with other objects. By contrast, the following will prevent him doing anything other than examining to any item: "Zodiac" The Secluded Alley is a room. The Capricorn Killer is a man in the Secluded Alley. The player carries a can of mace and a roll of duct tape. Instead of doing something other than examining something in the presence of the Capricorn Killer: say "You dare not attempt it!" Test me with "x me / x killer / touch killer / smell mace / sing". But notice that because we specified "examining something", actions that take no object (like sing) are still not affected. The most strict statement would be "Zodiac" The Secluded Alley is a room. The Capricorn Killer is a man in the Secluded Alley. The player carries a can of mace and a roll of duct tape. Instead of doing something other than looking or examining in the presence of the Capricorn Killer: say "You dare not attempt it!" Test me with "x me / x killer / touch killer / smell mace / sing". Because we left "something" out, now the pattern does not have to match an activity with an object; it will match any activity at all. Singing too will be deemed too risky in the presence of our sinister foe. But we do need to make an exception for "look", or else we won't get even the room description. Example 97 (*): Ming Vase ATTACK or DROP break and remove fragile items from play. In emulation of a certain annoying aspect of the original Adventure, in which there is a Ming vase that cannot safely be dropped: "Ming Vase" A thing can be strong or fragile. A thing is usually strong. Instead of attacking or dropping a fragile thing: remove the noun from play; say "[The noun] breaks into thousands of pieces!" The Cave is a room. The Ming vase is carried by the player. The vase is fragile. We could also implement an additional refinement from Adventure, that a fragile thing is safe if dropped when there is a cushion nearby. The pillow is a portable supporter. It is carried by the player. Instead of dropping a fragile thing when the pillow is in the location: try putting the noun on the pillow instead. After putting a fragile thing on the pillow: say "You set [the noun] down gently on the pillow." Test me with "drop pillow / drop vase / get vase / get pillow / drop vase". In this rule, the pillow is the second noun; if we had a general rule about setting fragile things on soft things, we could say "You set [the noun] down gently on [the second noun]." for the same effect. If we wanted to be more refined, we would provide extra code so that breaking a container or a supporter would leave behind their contents. We will see how to do that later. Example 98 (*): Beachfront An item that the player can't interact with until he has found it by searching the scenery. Suppose we have our player, a detective, searching for evidence; we don't want him to be able to use this evidence until he has performed the action that reveals it, but after that it should be visible in the room when he looks. A simple way to do this is to start the object -- an envelope, in this scenario -- out of play, and only move it into the location when the player looks for it: "Beachfront" The Stuffy Office is a room. "The windows are closed, making the sultry air even more unbearable. A narrow slice of Caribbean blue is visible between the scuba gear rental shop and the recreated 17th century pirate tavern. The office is cheerfully furnished with wicker chairs and white curtains, but the tropical decorating scheme stopped at the desk, which is heavy oak and absolutely covered with papers." The heavy oak desk is a supporter in the stuffy office. It is scenery. Understand "paperwork" as the desk. The creamy envelope is an openable container. The description is "There is no return address on the outside of the envelope, just the address of the Doctor's office -- but the legs of the capital A are rubbed down in a characteristic way, and the top of every R is open. There's no question that it comes from the same typewriter as the blackmail note." In the envelope is a letter. The envelope can be found or lost. The envelope is lost. Instead of searching the desk when the envelope is lost: now the envelope is found; say "You rifle through the piles of bills and notices; invitations to conventions; advertisements for high-end prescription drugs; pink carbon sheets bearing patients['] names and medical identification numbers in spidery, elderly handwriting. Almost at the bottom of the heap, you find what you were looking for: a creamy envelope with the address typed."; move the envelope to the desk. Here we've changed the property of the envelope to keep track of the fact that it has been found, so that if the player tries again, he won't find anything more. Instead of searching the desk: say "Further investigation of the desk reveals nothing else suspicious." Notice that we have two rules that apply to "searching the desk", but one of them has a more specific set of parameters ("when the envelope is lost"). This means that Inform will consult that rule first and use it if it applies; it will only carry out our plain vanilla "instead of searching the desk" rule when the more restricted rule is not relevant. Test me with "x envelope / x desk / search desk / look / get envelope / x envelope". Example 99 (**): Today Tomorrow A few notes on "In the presence of" and how it interacts with concealed objects. Rules about concealment will affect "in the presence of", too. For instance, suppose we have a man with a pocket pet: "Today Tomorrow" The Temporary Employment Office is a room. "'Tomorrow's Temporary Workers - Today!' proclaims the logo over the door. The office is divided into two areas, the inner sanctum where you take calls and fiddle with the computer, and the outer area where workers take skill exams and watch inspirational videos ('Earn your way to partial benefits!', 'Vacation days and you!', 'Temping the Tomorrow Way', etc.)." Maya is a woman in the Office. "Your coworker Maya sits at her own computer, diligently modifying all the [one of]pay rates in the database down from $9.00 an hour to $8.96[or]billing rates in the database up from $25.00 an hour to $25.04[purely at random]." She wears a trenchcoat. She carries a chihuahua. The description of Maya is "[if Maya is wearing the trenchcoat]She's wearing a trenchcoat, in a bizarre bid to keep your boss unaware of the chihuahua in her pocket. 'Because petsitters are really expensive!' she explained to you in an urgent hiss this morning over the coffeemaker. [otherwise]She looks cold. [end if]To all appearances, she is carrying [a list of unconcealed things carried by Maya]." Maya's computer is scenery in the Employment Office. The description is "You can't see the screen from here, but she was perfectly happy to tell you what she was doing." Rule for deciding the concealed possessions of someone (called carrier): if the particular possession is the chihuahua and the carrier wears the trenchcoat, yes; otherwise no. Instead of eating something in the presence of the chihuahua: say "[The chihuahua] yips at you! Maya looks despairingly at [the noun], which is obviously inciting it." The desk is scenery in the Office. On the desk are a multi-line telephone and a printer. The description of the printer is "Every morning, this instrument of torture spits out a list of the assignments you have to fill - professional, attractive receptionist with level three Excel certification, at $7.05 an hour; that sort of thing. You spend the ensuing three hours trying to meet its tyrannical demands." The description of the multi-line telephone is "Line three blinks urgently at you. You'll pick it up again as soon as you can remember who it was you put on hold." The player carries a double bacon cheeseburger and a chocolate shake. Understand "milkshake" or "beverage" as the shake. The description of the cheeseburger is "A minor self-indulgence to make up for the fact that you have to work through lunch." The cheeseburger is edible. The shake is edible. The description of the shake is "It has the consistency of spackle and is no longer cold, but there is some chocolatey goodness in it still." Understand "burger" or "hamburger" as the cheeseburger. Instead of drinking the chocolate shake: try eating the shake instead. Test me with "x maya / x cheeseburger / drink shake / eat cheeseburger". Unless we somehow get the trenchcoat away from Maya, the chihuahua will not be in view, and will not intervene in our lunch. All very well for the player character, but not so interesting to the story... To this end, we might add an unfortunate event, courtesy of later chapters: The time of day is 11:45 AM. At 11:47 AM: say "Your boss pokes his head in, temporarily free of the round of conference calls that occupy all his days. 'Maya,' he says. 'Your coat?' He shakes his head, clucking sadly. 'It doesn't say professional!' But mercifully Maya manages to take it off so slowly that he doesn't glimpse her pet before her phone rings again."; now Maya carries the trenchcoat. Example 100 (*): Veronica An effect that occurs only when the player leaves a region entirely. Suppose that we want to have something happen when the player leaves a region we've defined. "Instead of going from (the region)..." will not suffice for this, because this rule will be invoked every time the player successfully leaves a room within the region, whether or not he is going to a room that is also in the same region. Instead we need a rule that is a bit more specific, like this: "Veronica" Neptune is a region. Tijuana is a room. High School is north of Tijuana. It is in Neptune. Detective Offices is west of High School. It is in Neptune. The player is in High School. Instead of going from Neptune to a room which is not in Neptune: say "It's a bad time to leave Neptune." Test me with "s / w / e". Example 101 (**): A&E Using regions to block access to an entire area when the player does not carry a pass, regardless of which entrance he uses. Rules about going to regions make it easy to exclude the player from a large portion of the map, even if there are many connecting paths to the region. For instance, in this story it would be annoying to have to write a rule about all four exits by which the player could reach the film set area: "A&E" Winding Street is a room. Winding Street is west of Duck Pond. Sloping Street is north of Winding Street, northwest of Duck Pond, west of Stately Lawn, and southwest of Stately Home. Stately Lawn is north of Duck Pond. Stately Home is north of Stately Lawn. Film Set is a region. Duck Pond, Stately Lawn, and Stately Home are in Film Set. Instead of going to Film Set when the player does not carry the VIP Pass: say "A burly studio guard materializes in your path, convincing you that you would prefer to be elsewhere." The VIP Pass is in the garbage can. The garbage can is in Sloping Street. After going to the Film Set: say "Success! At last you are inside the set of 'Prouder and More Prejudiced'. Next step: locating Mr Firth."; end the story finally. Test me with "e / n / e / get pass / e". Example 102 (***): Polarity A "go back" command that keeps track of the direction from which the player came, and sends him back. The main trick of this is always to record where the player has gone when he has just moved. "Polarity" The former location is a room that varies. Here we record where the player has been before moving him; by calling this the "first carry out going rule", we make sure that this rule is followed during the going action before any other pieces of the movement occur. For more detail, see the chapters on advanced actions and on rules. First carry out going rule: now the former location is the location. Understand "go back" as retreating. Understand "back" or "return" or "retreat" as retreating. Retreating is an action applying to nothing. Carry out retreating: let way be the best route from the location to the former location, using doors; if way is a direction, try going way; otherwise say "You can't see an open way back." And to deal with the case where the player has not yet moved: When play begins: now the former location is the Dome. Instead of retreating when the former location is the location: say "You haven't gone anywhere yet." Dome is a room. North of Dome is North Chapel. South of the Dome is South Chapel. West of the Dome is Western End. Quiet Corner is northwest of the Dome, north of Western End, and west of North Chapel. Loud Corner is east of North Chapel, northeast of Dome, and north of Eastern End. Eastern End is north of Dim Corner and east of Dome. Dim Corner is southeast of Dome and east of South Chapel. Ruined Corner is southwest of Dome, west of South Chapel, and south of Western End. The church door is east of Eastern End and west of the Courtyard. The church door is a door. Test me with "back / n / go back / e / open door / go through door / go back". Example 103 (***): Bumping into Walls Offering the player a list of valid directions if he tries to go in a direction that leads nowhere. "Bumping into Walls" First we add an instruction to determine which ways lead to other rooms. Definition: a direction (called thataway) is viable if the room thataway from the location is a room. Now we build in the instruction for what Inform should say if the player tries to head in a direction that leads nowhere: Instead of going nowhere: let count of exits be the number of viable directions; if the count of exits is 0, say "You appear to be trapped in here." instead; if the count of exits is 1, say "From here, the only way out is [list of viable directions]."; otherwise say "From here, the viable exits are [list of viable directions]." There is no theoretical reason why we have to define "count of exits" here: we could, if we wanted, just say "if the number of viable directions is 0", "if the number of viable directions is 1", and so on. However, each calculation of a "viable direction" takes a bit of computing power, so there is some slight savings in not requiring the game to count viable directions more than once in this routine. Dome is a room. North of Dome is North Chapel. South of the Dome is South Chapel. West of the Dome is Western End. Quiet Corner is northwest of the Dome, north of Western End, and west of North Chapel. Loud Corner is east of North Chapel, northeast of Dome, and north of Eastern End. Eastern End is north of Dim Corner and east of Dome. Dim Corner is southeast of Dome and east of South Chapel. Ruined Corner is southwest of Dome, west of South Chapel, and south of Western End. The Crypt is below the dome. The church door is east of Eastern End and west of the Courtyard. The church door is a door. Test me with "u / n / n / e / n / s / u / open door / e / n". Example 104 (*): Mattress King Adding extra phrasing to the action to PUSH something in a direction. By default, when the player pushes something a direction, Inform checks to make sure that the object is pushable between rooms. If not, it blocks the action; if so, it carries out a normal going action with the pushed object taken along. Also by default, this action produces only a description of the new room that we've traveled into. But suppose we would like to print a short message describing the pushing action first: "Mattress King" Monica's Bedroom is a room. The Living Room is south of Monica's Bedroom. Rachel's Bedroom is south of the Living Room. After going a direction (called way-pushed) with something (called the thing-pushed): say "You push [the thing-pushed] [way-pushed] to [the location]."; continue the action. The race car bed is an enterable supporter in Monica's Bedroom. It is pushable between rooms. Test me with "push bed south". Example 105 (*): No Relation A car which must be turned on before it can be driven, and can only go to roads. We need to designate certain rooms as roads. Since the status of being a road will not change during play, we do this with a kind: "No Relation" A road is a kind of room. Definition: a room is offroad if it is not a road. Instead of going by a vehicle (called the auto) to somewhere offroad: say "You can't drive [the auto] off-road." Trafalgar Square is a road. "The Square is overlooked by a pillared statue of Admiral Lord Horatio Nelson (no relation), naval hero and convenience to pigeons since 1812." The National Gallery is north of Trafalgar Square. The Strand is east of Trafalgar Square. The Strand is a road. The car is a vehicle in Trafalgar Square. The ignition is a device. The ignition is part of the car. Instead of going by the car when the ignition is switched off: say "The ignition is off at the moment." Instead of switching on the car, try switching on the ignition. Instead of switching off the car, try switching off the ignition. Test me with "get in car / n / e / turn on car / n / e / get out / w / n / s / e / get in car / turn off car / w / turn on ignition / w". (In the course of the writing of Inform 7, much of Trafalgar Square was pedestrianised, making this example already out of date.) A further technical note: notice "going by a vehicle" in the above rule, rather than "going by something". A rule such as "Instead of going by something..." will be matched whenever the player tries to go some direction while in an enterable object, whether or not that object is actually capable of movement. This is sometimes useful, but in this case we want the warning to apply only when the player is in a vehicle; if we added Trafalgar Square's statue bases to the scenario, we would not want You can't drive the pedestal off-road. So we restrict the rule to "Instead of going by a vehicle..." Example 106 (**): One Short Plank A plank bridge which breaks if the player is carrying something when he goes across it. Pushing anything over the bridge is forbidden outright. "One Short Plank" The East Jungle is a room. The plank bridge is west of the East Jungle and east of the West Jungle. The plank is an open unopenable door. "A precarious plank bridge extends [if the location is West Jungle]east[otherwise]west[end if] across the chasm." The description of the plank is "Extremely fragile and precarious." Instead of going through the plank when the player is carrying something: say "You step gingerly across the plank, which bows under your weight. But your meagre possessions are the straw which breaks the camel's back!"; end the story. After going through the plank: say "You step gingerly across the plank, grateful that you're not burdened."; continue the action. There is a feather in the East Jungle. But indeed, why stop there? The gigantic stone ball is a thing in the West Jungle. It is pushable between rooms. Before going through the plank with something: say "Surely you jest." instead. Test me with "w / e / w / push ball e / e / get feather / w". Example 107 (***): Provenance Unknown Allowing something like PUSH TELEVISION EAST to push the cart on which the television rests. Suppose we have a series of items that might be stacked on top of one another -- say a heavy television on a rolling cart, and we want the player to be able to move the cart with PUSH TELEVISION EAST just as well as with PUSH CART EAST. This takes a little redirection, using a setting action variables rule. This is not a kind of rule we've encountered yet, and in fact we won't meet it until the Advanced Actions chapter; it is included here for the convenience of authors who want to modify the effect of pushing without reading that far ahead: "Provenance Unknown" Setting action variables for pushing something to: if the noun is enclosed by a pushable between rooms thing (called the pushed item) which is in the location: now the noun is the pushed item instead. This rule says that any time we push an object that is on top of a stack of pushable objects, we should transfer the action to the item at the bottom of the stack. The rest is merely a test case. The heavy golden idol is on a roller board. The roller board is on a hovercraft. The hovercraft, the tea trolley, and the skateboard are pushable between rooms. The hovercraft is in Zeta Proximan Dig Field. Zeta Proximan Dig Field is a room. "During the day, the field is massed with sweating native workers, overseers, and officials from central command. Now the spades, trowels, brushes, metal detectors, ground probes, plumb lines, and sighting tripods have been laid aside. All that remains are the trenches and the fine grey dust that blows slowly across them; the moonlight; and the just-emerging outlines of an ancient and alien wall." The Hover-Road is west of the Dig Field. "A long road hastily laid down, stretching east to west, from the dig site toward the safety of the city." When play begins: say "You have, at last, loaded your illicit cargo without setting off any of the many and sensitive alarms set here; now it remains only to sneak out of the area, under the light of Zeta Proxima's lone green moon." Test me with "push idol west / look / push roller board east / look". Example 108 (***): Zorb Replacing the message the player receives when attempting to push something that isn't pushable, and also to remove the restriction that objects cannot be pushed up or down. There are two aspects of Inform's handling of pushable objects that are particularly prime for modification. One is that we may want to change the language used to refuse the pushing of unpushable objects. Second, Inform by default assumes that it is impossible to push objects in up or down directions. This makes lots of sense if the player is trying to push a wheelbarrow up a ladder; it makes less sense if instead we're pushing a ball up a slope. We solve both problems with some syntax borrowed from the chapter on rulebooks: in the first case, we replace the old rule with a new one with more friendly phrasing; in the second, we remove the rule entirely. More about how to do this is described in the rulebooks chapter; and in general we can find out what rules contribute to any given action by looking at the Actions index. In this case, the action is "pushing it to", which has its own set of prerequisites (called check rules) that make sure the object can safely be pushed, before turning processing over to the going action. "Zorb" Section 1 - Procedure The new can't push unpushable things rule is listed instead of the can't push unpushable things rule in the check pushing it to rules. Include Plurality by Emily Short. [This allows us to use the "is-are" replacement in the following rule.] This is the new can't push unpushable things rule: if the noun is not pushable between rooms: say "[The noun] [is-are] not amenable to being pushed from place to place." instead. The can't push vertically rule is not listed in any rulebook. And now to provide a scenario where the player can push something up and down a hillside. Most of the rest of the example is there for local color and to provide a way to demonstrate these rule adjustments: Section 2 - Scenario The Steep Hill is a room. The Crest is above Steep Hill. The Valley is below Steep Hill. The flat rock is a fixed in place thing in the Steep Hill. The Zorb is a transparent open enterable container in the Steep Hill. "[if the player props the Zorb]The Zorb rests here, kept from further rolling by your support[otherwise]The Zorb is here[end if].". It is pushable between rooms. The description of the Zorb is "A giant plastic inflatable ball, like a hamster ball for humans[if someone is in the Zorb]. Inside [is-are list of people in the Zorb][end if]." Lucy is a woman in the Zorb. Carry out going with the Zorb when the Zorb contains Lucy: say "Lucy whoops delightedly as she rides along in the Zorb." Every turn when the Zorb is not in the Valley and the player does not prop the Zorb: let next room be the room down from the location of the Zorb; if the player is not in the Zorb and the player can see the Zorb: say "The Zorb succumbs to gravity and rolls down toward [the next room]."; move the Zorb to the next room; if the player is in the Zorb: say "The Zorb rolls you down the hill!"; try looking; otherwise if the player can see the Zorb: say "The Zorb rolls ponderously but inevitably into the vicinity."; Propping relates one person to one thing. The verb to prop (it props, they prop, it propped, it is propped, it is propping) implies the propping relation. Carry out going with the Zorb: now the player props the Zorb. Before doing something when the action requires a touchable noun: if the noun is not the Zorb, now the player does not prop the Zorb. Check waving hands when the player is propping something (called casualty): try the player releasing the casualty. Carry out entering the Zorb: now the player does not prop the Zorb. Understand "let go of [something]" or "let [something] go" or "release [something]" or "free [something]" as releasing. Releasing is an action applying to one thing. Check releasing: if the player carries the noun: try dropping the noun instead. Check releasing: if the player does not prop the noun: say "You are not supporting [the noun]." instead. Carry out releasing: now the player does not prop the noun. Report releasing: say "You let go of [the noun]." Test me with "d / push zorb up / look / push zorb up / wave / d / d / push zorb up / release zorb / d / push zorb up / touch rock / push the flat rock south". Example 109 (*): Dearth and the Maiden Our heroine, fallen among gentleman highwaymen, is restrained by her own modesty and seemliness. The following example, indebted to the late Georgette Heyer, is suggestive: "Dearth and the Maiden" The Chequers Inn is a room. "The room is panelled and ceilinged in oak, with blue curtains to the windows and blue cushions on the high-backed settle by the fire." An oil painting is in the Inn. "An oil painting hangs upon one wall, a lascivious work from the Indes in which a very bendy, sloe-eyed courtesan - but no." A man called Mr Carr is in the Inn. "Standing bashfully aside is one Mr Carr, who we have been led to understand is by profession a Highwayman (yet whose visage oddly recalls Lord John Carstares, disgraced eldest son of the Earl of Wyncham)." Kissing Mr Carr is unmaidenly behaviour. Doing something to the painting is unmaidenly behaviour. Instead of unmaidenly behaviour in the Inn, say "How unmaidenly! Why, one might just as wantonly strip a rose of its petals, letting each fragrant leaf flutter slowly to the ground." Test me with "examine painting / take painting / kiss mr carr". Example 110 (***): Mimicry People who must be greeted before conversation can begin. Suppose we want to add a sense of some conversational flow, so that the player is forced to acknowledge the presence of people before beginning detailed conversations with them. We collect all speech actions into a single category: "Mimicry" Asking someone about something is speech. Telling someone about something is speech. Answering someone that something is speech. Asking someone for something is speech. And then write a general rule. Before speech in the presence of an ungreeted person: try waving hands. One complication is that "asking someone to try doing something", which describes commands such as FRED, GO SOUTH, cannot be made into a kind of action. This requires its own rule: Before asking someone to try doing something in the presence of an ungreeted person: try waving hands. Now we define what greetings are going to look like: Check waving hands: unless the player can see someone who is not the player, say "You are alone." instead. Carry out waving hands: say "You nod hello to [the list of ungreeted people who can be seen by the player]."; now every ungreeted person who can be seen by the player is greeted. The block waving hands rule is not listed in the check waving hands rulebook. Because of the way we've defined the command, this will now also work if the player waves. A person can be greeted or ungreeted. A person is usually ungreeted. The player is greeted. And now the scenario: The International Convention of Mimes is a room. Lester, Harold, Geoff, Kwame, and Peter are men in the Convention. Elouise is a woman in the Convention. The Invisible Box is an enterable container in the Convention. "You can detect, from the way people keep leaning on it, an invisible box in the middle of the room." Lester carries a bowler hat. Instead of speech in the presence of someone: describe poor reception. Definition: a person is other if it is not the player. At 9:01 AM: move Phineas to the location; say "A mime called Phineas appears from the non-existent bathroom." Phineas is a man. A persuasion rule: describe poor reception; persuasion fails. To describe poor reception: if the player is in the Invisible box, say "Everyone convulses with silent laughter as you try to shout from within the invisible box."; otherwise say "You attempt to convey your meaning with gesture and interpretive dance, but [the list of visible other people] scorn[if the number of visible other people is 1]s[end if] your performance, refusing to respond." Test me with "ask lester about work / lester, east / ask lester for bowler / lester, nice not talking to you / get in box / ask lester for hat / phineas, east". Example 111 (*): Y ask Y? Noticing when the player seems to be at a loss, and recommending the use of hints. Suppose we'd like to watch for signs that the player is floundering, and if we see them, recommend that he try the hints. There are probably more sophisticated diagnostics, but as a first cut, let's assume that a player who repeatedly reviews descriptions of objects he's already seen, looks around the room, and takes inventory, is at a loss for more productive activities. So then... "Y ask Y?" A thing can be examined or unexamined. A thing is usually unexamined. Carry out examining something: now the noun is examined. Taking inventory is acting confused. Looking is acting confused. Examining an examined thing is acting confused. After acting confused for the sixth turn: say "(If you are feeling lost, try typing HELP for suggestions.)" And now we write a scenario which will, alas, rather encourage even a deft and clueful player to play as though he were hopelessly confused: The story headline is "or: Bad Author, No Biscuit". The description of a thing is usually "Hm. [The item described] reminds you quite a lot of [a random visible thing which is not the item described]." The Yurt is a room. Food is a kind of thing. Food is always edible. In the Yurt are a yam and a dish of yakitori. The yam and the yakitori are food. The description of food is "Well, at least it's not [a random edible thing which is not the item described]." In the Yurt is an animal called a yapok. The player wears a yukata. The player carries a yataghan. Every turn: if a random chance of 1 in 2 succeeds and something is examined: say "Your eye is attracted by some kind of surreptitious movement from [the random examined thing]."; otherwise if the player carries something and a random chance of 1 in 3 succeeds: say "[The random thing carried by the player] tries to slip from your grasp." Test me with "x yam / x yam / look / x yam / i / look / i / help / quit". And finally a little dollop of perversity from a later chapter: Check quitting the game: say "You're sure? "; if player consents, say "[line break]You were getting close to a breakthrough, you know.[line break]"; otherwise stop the action. Understand "help" as a mistake ("You're doing fine! Just keep at what you're doing now."). Example 112 (****): A Day For Fresh Sushi A complete story by Emily Short, called "A Day for Fresh Sushi", rewritten using Inform 7. Noteworthy is the snarky commenter who remarks on everything the player does, but only the first time each action is performed. The following is an almost-completely-faithful rewrite of Emily Short's "A Day for Fresh Sushi", which was originally written using the (very different) Inform 6 programming language. The -- let us be honest and call it a gimmick -- of this game is the evil fish, who has some unpleasant remark to offer on pretty much every action. But the effect would wear off fast if he repeated himself, so these comments need to be single-use only. Inform 7's repeated action syntax makes it much tidier to write the same scenario, so: "A Day For Fresh Sushi" by Emily Short. The story headline is "Your basic surreal gay fish romance". The Studio is a room. "[if visited]Decorated with Britney's signature flair. It was her innate sense of style that first made you forgive her that ludicrous name. And here it is displayed to the fullest: deep-hued drapes on the walls, the windows flung open with their stunning view of old Vienna, the faint smell of coffee that clings to everything. Her easel stands over by the windows, where the light is brightest.[otherwise]This is Britney's studio. You haven't been around here for a while, because of how busy you've been with work, and she's made a few changes -- the aquarium in the corner, for instance. But it still brings back a certain emotional sweetness from the days when you had just met for the first time... when you used to spend hours on the sofa... You shake your head. No time for fantasy. Must feed fish.[end if]" Instead of smelling the Studio: say "The evil fish notices you sniffing the air. 'Vanilla Raspberry Roast,' it remarks. 'You really miss her, don't you.' You glance over, startled, but the fish's mouth is open in a piscine equivalent of a laugh. You stifle the urge to skewer the thing..." Instead of jumping: say "'Er,' says the fish. 'Does that, like, EVER help??'" Instead of going nowhere: say "You can't leave until you've fed the fish. Otherwise, he'll complain, and you will never hear the end of it." The cabinet is an openable closed container in the Studio. It is fixed in place. "A huge cabinet, in the guise of an armoire, stands between the windows." The description is "Large, and with a bit of an Art Nouveau theme going on in the shape of the doors." Understand "armoire" as the cabinet. Instead of looking under the cabinet for the first time: say "'Dustbunnies,' predicts the fish, with telling accuracy. It executes what for all the world looks like a fishy shudder. 'Lemme tell you, one time I accidentally flopped outta the tank, and I was TWO HOURS on the floor with those things STARING ME IN THE NOSE. It was frightening.'" After opening the cabinet for the first time: say "'There ya go,' says the fish. 'The girl is getting WARMER.'" After closing the cabinet for the first time: if the fish food is not found, say "'Ooh, what do you think, Bob? I think we're going to have to dock the girl a few points. HAVE ANOTHER LOOK, sweetcakes, there's a doll.'" The cabinet contains some paints and some cloths. The description of the paints is "A bunch of tubes of oil paint, most of them in some state of grunginess, some with the tops twisted partway off." After taking the paints for the first time: say "'Boy,' says the fish, apparently to himself, 'I sure hope that's some food she's finding for me in there. You know, the yummy food in the ORANGE CAN.'" After examining the paints for the first time: say "'Tons of useful stuff in there,' hollers in the fish, in a syncopated burble." The description of the cloths is "Various colors of drapery that Britney uses to set up backgrounds and clothe her models. She does a lot of portraiture, so this comes in handy. It's all a big messy wad at the moment. Organized is not her middle name." Understand "drapery" or "cloth" as the cloths. The indefinite article of the cloths is "a heap of". [see 3.17] Instead of searching or looking under the cloths for the first time: now the player is carrying the fish food; now the fish food is found; say "Poking around the cloths reveals -- ha HA! -- a vehemently orange can of fish food." Instead of showing the cloths to the fish: say "'What are you, some kind of sadist? I don't want to see a bunch of cloths! What kind of f'ing good, 'scuse my French, is that supposed to do me? I don't even wear pants for God's sake!' He really looks upset. You start wondering whether apoplexy is an ailment common to fish." After examining cloths for the first time: say "'Whatcha looking at? I can't see through the doors, you know.'" There is a can of fish food. Understand "canister" as the can. The description is "A vehemently orange canister of fish food." The fish food can be found or hidden. The fish food is hidden. Instead of giving the can to the fish: say "'I don't want the whole can, GeniusChyk. Just feed me and we'll ALL be happy, 'kay?" Instead of showing the can to the fish: say "'That's the ticket, sweetie! Bring it on.'" Instead of opening the can: say "'Oh, for--!' The evil fish breaks out in exasperation and hives. 'Screw the screwing around with the screwtop. SHE never has to do that.' 'Well, SHE is not here,' you reply. 'What do you suggest?' '>FEED FISH<' says the fish promptly, making fishy faces and pointing at you with his fin. 'Simplicity. Try it.'" Instead of inserting the can into something: say "'HelLLLOOO,' screams the fish. 'Whatever happened to FEEDING MEEE?'" The easel is a supporter in the Studio. It is scenery. On the easel is a painting. Understand "portrait" or "image" as the painting. The description of the painting is "Only partway finished, but you can tell what it is: Britney's mother. You only met the old woman once, before she faded out of existence in a little hospice in Salzburg. In the picture, her hands are grasping tightly at a small grey bottle, the pills to which she became addicted in her old age, and strange, gargoyle-like forms clutch at her arms and whisper in her ears. But the disturbing thing, the truly awful thing, is the small figure of Britney herself, down in the corner, unmistakable: she is walking away. Her back turned. You thought she'd finally talked this out, but evidently not. Still feels guilty for leaving. You only barely stop yourself from tracing, with your finger, those tiny slumped shoulders..." Instead of taking the painting, say "No, you'd better leave it. It'd freak her out if you moved it." Before examining the painting for the first time: say "A ferocious banging from the aquarium attracts your attention as you go to look at the painting. 'Hey!' screams the fish. 'She doesn't like strangers looking at her paintings before they're DOONNNE!' 'Shut up, you,' you reply casually. 'I'm not a stranger.' But the fish puts you off a little bit, and your heart is already in your mouth before you see the painting itself...". Instead of examining the painting more than once: say "Once is really enough. It's pretty much embedded in your consciousness now." After doing something to the painting: say "'So what's it of?' asks the fish, as you turn away. 'She never asks if I want to see them, you know?' 'Her mother,' you respond without thinking. 'Yeah? Man. I never knew my mother. Eggs, that's the way to go.'" The window is scenery in the Studio. The window can be openable. The window can be open. It is openable and closed. Understand "windows" as the window. The description of the window is "[if open]Through the windows you get a lovely view of the street outside. At the moment, the glass is thrown open, and a light breeze is blowing through.[otherwise]Through the windows, you get a lovely view of the street outside -- the little fountain on the corner, the slightly dilapidated but nonetheless magnificent Jugendstil architecture of the facing building. The glass itself is shut, however.[end if]" After opening the window for the first time: say "'Thank god some air,' says the fish. 'Man, it was getting hard to breathe in here.' Two beats pass. 'Oh wait.'" The table is scenery in the Studio. On the table is a vase. The vase is an open container. It is not openable. The description of the table is "A monstrosity of poor taste and bad design: made of some heavy, French-empire sort of wood, with a single pillar for a central leg, carved in the image of Poseidon surrounded by nymphs. It's all scaley, and whenever you sit down, the trident has a tendency to stab you in the knee. But Britney assures you it's worth a fortune." The description of the vase is "A huge vase -- what you saw once described in a Regency romance as an epergne, maybe -- something so big that it would block someone sitting at the table from seeing anyone else also sitting at the table. But it does function nicely as a receptacle for hugeass bouquets of flowers." Instead of looking under the table for the first time: say "'You're not going to find anything down there,' whines the fish. 'I mean, c'mon. It's the fricking floor. Please tell me you can see that. I can see that. I'm a myopic fish in a tank ten feet away and I can tell you there is nothing there but floor.'" After examining the table: say "'That there is MY PA,' says the fish, pointing at the scaley triton figure with one fin." Instead of inserting something which is not the bouquet into the vase: say "'Okay, so, what were you, raised in a barn? Normal folks like to use that for flowers. Or so I've observed.'" After inserting the bouquet into the vase for the first time: say "You settle the flowers into the vase and arrange them so that they look sprightly. 'Oooh,' says the fish. 'No one ever changes the plant life in HERE. It's the same seaw--' 'Cut me a break and cork it,' you reply tartly." The player is carrying a telegram, a bouquet, and a lingerie bag. The player is wearing a chef hat. The description of the telegram is "A telegram, apparently. And dated three days ago. [fixed letter spacing]TRIUMPH OURS STOP BACK SOON STOP BE SURE TO FEED FISH STOP[variable letter spacing]". [For printing options see 4.13.] Understand "yellow paper" as the telegram. After examining the telegram for the first time: say "'So,' blubs the evil fish. 'How about it? Little food over here?'" After examining the telegram: choose a random row in the Table of Insulting Fish Comments; say "[comment entry][paragraph break]". Table of Insulting Fish Comments comment "'Yeah, yeah,' says the fish. 'You having some trouble with the message, there? Confused? Something I could clear up for you?'" "'Oookay, genius kid has some troubles in the reading comprehension department.' The fish taps his head meaningfully against the side of the tank. 'I'm so hungry I could eat my way out, you get my meaning?'" "'I'll translate for you,' screams the fish in toothy fury. 'It says GIVE FOOD TO FISH!! How much more HELP do you NEED???" The description of the chef hat is "A big white chef hat of the kind worn by chefs. In this case, you. Just goes to show what a hurry you were in on the way out of the restaurant." Understand "big" or "white" or "chefs" or "chef's" as the chef hat. [Inform knows that this is clothing because the player starts out wearing it, so there's no need to say so separately.] The aquarium is a transparent open container in the Studio. It is not openable. "In one corner of the room, a large aquarium bubbles in menacing fashion." The description of the aquarium is "A very roomy aquarium, large enough to hold quite a variety of colorful sealife -- if any yet survived." Understand "tank" as the aquarium. The aquarium contains some gravel and some seaweed. Understand "little rocks" as the gravel. Understand "weed" as the seaweed. The description of the gravel is "A lot of very small grey rocks." The description of the seaweed is "Fake plastic seaweed of the kind generally bought in stores for exactly this purpose." A procedural rule while examining the aquarium: ignore the examine containers rule. After examining the gravel for the first time: say "The fish notices your gaze; makes a pathetic mime of trying to find little flakes of remaining food amongst the gravel." After examining the seaweed for the first time: say "'Nice, hunh?' blubs the fish, taking a stabbing bite out of one just by way of demonstration. 'Look so good I could eat it.'" The aquarium contains an animal called an evil fish. The description of the fish is "Even if you had had no prior experience with him, you would be able to see at a glance that this is an evil fish. From his sharkish nose to his razor fins, every inch of his compact body exudes hatred and danger." Instead of taking the evil fish: say "The fish swims adroitly out of range of your bare hand. 'Hey,' he says, and the bubbles of his breath brush against your fingers. 'Count yourself lucky I don't bite you right now, you stinking mammal.'" Instead of attacking the evil fish: say "Oh, it's tempting. But it would get you in a world of hurt later on." Instead of kissing the evil fish: say "You're saving all your lovin for someone a lot cuddlier." After examining the evil fish for the first time: say "The fish glares at you, as though to underline this point." After examining the evil fish for the second time: say "'If you're looking for signs of malnutrition,' says the fish, 'LOOK NO FURTHER!!' And it sucks in its gills until you can see its ribcage." An every turn rule: choose a random row in the Table of Fish Banter; say "[comment entry][paragraph break]". Table of Fish Banter comment used "'Hey, nice SKIN TONE,' shouts the evil fish. His words reach you in a spitting gurgle of aquarium water. 'You gone over to a pure eggplant diet these days?'" 0 "The evil fish is floating belly up! ...oh, curse. He was toying with you. As soon as he sees you looking, he goes back to swimming around." 0 "The evil fish darts to the bottom of the tank and moves the gravel around with his nose." 0 "The evil fish is swimming around the tank in lazy circles." 0 "The evil fish begins to butt his pointy nose against the glass walls of the tank." 0 The description of the bouquet is "Okay, so it's silly and sentimental and no doubt a waste of money, of which there is never really enough, but: you miss her. You've missed her since ten seconds after she stepped aboard the shuttle to Luna Prime, and when you saw these -- her favorites, pure golden tulips like springtime -- you had to have them." Understand "flowers" or "tulip" or "tulips" as the bouquet. After examining the bouquet for the first time: say "'Oh, you shouldn't have,' says the fish. 'For me??' You just respond with a livid glare." Instead of smelling the bouquet for the first time: say "'Mmm-mm,' says the fish. 'Damn, I sure wish I had olfactory abilities. Hey, if I did, I might be even better at noticing the presence or absence of FOOD.'" The description of the lingerie bag is "You grant yourself the satisfaction of a little peek inside. You went with a pale, silky ivory this time -- it has that kind of sophisticated innocence, and it goes well with the purple of your skin. A small smirk of anticipation crosses your lips." After examining the lingerie bag for the first time: say "'What's in THERE?' asks the fish. 'Didja bring me take-out? I don't mind Chinese. They eat a lot of carp, but what do I care? I'm not a carp. Live and let live is what I s--' 'It's NOT take-out.' You stare the fish down and for once he actually backstrokes a stroke or two. 'It's PRIVATE.'" After examining the lingerie bag for the second time: say "'If it's not take-out, I don't see the relevance!' shouts the fish. 'Food is what you want in this situation. Food for MEEEE.'" Understand the command "feed" as something new. Understand "feed [something]" as feeding. Feeding is an action applying to one visible thing. Check feeding: if the noun is not the evil fish, say "That doesn't make much sense." instead; if the player is not carrying the fish food, say "You need the fish food first." instead. Carry out feeding: increment the score; say "Triumphantly, you dump the remaining contents of the canister of fish food into the tank. It floats on the surface like scum, but the fish for once stops jawing and starts eating. Like a normal fish. Blub, blub.[paragraph break]"; say "[bold type] *** TWO HOURS LATER ***[roman type][paragraph break]'So,' Britney says, tucking a strand of hair behind your ear, 'where shall we go for dinner? Since I made the big bucks on this trip, it's my treat. Anywhere you like.'[paragraph break]'I've had a hankering all day,' you admit, as the two of you turn from the shuttle platform and head toward the bank of taxis. 'I could really go for some sashimi right now.'"; end the story finally. Before feeding the fish food: try feeding the evil fish instead. When play begins: say "You're on the run. You've got a million errands to do -- your apartment to get cleaned up, the fish to feed, lingerie to buy, Britney's shuttle to meet-- [paragraph break]The fish. You almost forgot. And it's in the studio, halfway across town from anywhere else you have to do. Oh well, you'll just zip over, take care of it, and hop back on the El. This'll be over in no time.[paragraph break]Don't you just hate days where you wake up the wrong color?[paragraph break]". The maximum score is 1. Test me with "x fish / g / kiss fish / x aquarium / x gravel / x seaweed / i / x telegram / x bouquet / smell bouquet / x lingerie / g / x hat / x window / open window / x painting / g / x cabinet / open cabinet / x cloths / search cloths / open food / feed fish". Example 113 (***): Don Pedro's Revenge Combat scenario in which the player's footing and position changes from move to move, and the command prompt also changes to reflect that. Suppose our game features a detailed simulated combat between the player character and his opponent. He might have several weapons available, and several types of attack available; and at any given time he might be perched up in the rigging of his ship, standing on the open deck, or boxed in between some barrels. His options will vary depending on his position, and obviously it would detract from the pacing to make the player keep LOOKing in the middle of combat in order to remind himself where he is. Instead, we'll roll this information into the command prompt: "Don Pedro's Revenge" The Deck of the Helene Marie is a room. "The two crews are embattled all around you, but your attention is reserved for your particular enemy: Don Pedro." Table of Random Prompts position prompt boxed "So securely boxed-in that you can really only parry or thrust, you try to " boxed "Trapped between your barrels, you decide to " perched "Able to slice at your attackers but not to advance or retreat, you choose to " perched "Perched up here with the advantage of height (but little mobility), you attempt to " free "Out on the open deck with no impediments, free to advance or retreat, you decide to " When play begins: reset the prompt. Every turn: reset the prompt. To reset the prompt: sort the Table of Random Prompts in random order; repeat through the Table of Random Prompts: if the position entry is the placement of the player: now the command prompt is prompt entry; stop. After reading a command: say conditional paragraph break. A placement is a kind of value. The placements are boxed, perched, free. The player has a placement. The player is free. Understand "retreat" or "parry" as retreating. Retreating is an action applying to nothing. Check retreating: if the player is perched, say "You can't move backward or parry very successfully from this position." instead. Carry out retreating: now the player is boxed; say "You protect yourself, but end up wedged in between two barrels." Understand "thrust" or "advance" as advancing. Advancing is an action applying to nothing. Check advancing: if the player is perched, say "You can't move forward from here, only slash." instead. Carry out advancing: now the player is free; say "You push forward aggressively, making your way to the open deck." Instead of jumping: now the player is perched; say "You leap and swing yourself boldly up into the rigging, leaving your attackers beneath you." Instead of jumping when the player is perched: now the player is free; say "You leap down from your position, into the middle of the deck." Test me with "advance / jump / advance / retreat / jump / retreat / retreat / advance". Of course, this won't be much fun until we also provide the player with a few weapons, some more fighting maneuvers, and, most of all, a Don Pedro to defeat. Example 114 (*): Politics as Usual Have the status line indicate the current region of the map. Suppose a game with a large map entirely subdivided into regions. We could define: "Politics as Usual" When play begins: now the right hand status line is "[map region of the location]". Washington is west of Idaho. Red is a region. Blue is a region. Idaho is in red. Washington is in blue. Test me with "e / w". Note that, since regions can be stacked, we technically can be within more than one region at once. In the Port Royal example, for instance, the Tavern region is inside the Inland region. If there is any ambiguity, "the map region of the location" will be construed as "the smallest region that the location belongs to": so we would see "Tavern" rather than "Inland" in the status bar, when the player was in the Feathers or the Feathers Bedroom. Some extra finesse would be necessary if the names of map regions were very long or if there were some rooms that were not considered to belong to any region at all. Example 115 (***): Centered Replacing the two-part status line with one that centers only the room name at the top of the screen. If we want to lay out the status line in some other way than with left-hand and right-hand entries, it is possible to do this as well. Later we will learn about the "rule for constructing the status line", but here is a basic effect using this rule and an Inform extension included as part of the standard distribution, called Basic Screen Effects. "Centered" When play begins: say "After months of boring through the Earth's crust in this metal-jawed vehicle, you break through..." The Hollow Core is a room. "Truly a magnificent sight: the land curves up away from you in every direction, covered with the cities and fields of the Core People. Molten rock runs in the canals, bringing heat and light to every home. At the center of the Earth hangs a dense black sun." Include Basic Screen Effects by Emily Short. Rule for constructing the status line: center "[location]" at row 1; rule succeeds. Test me with "look". Basic Screen Effects also provides a mechanism for building complicated status lines of more than one row. To read its documentation, we include the extension, press Go!, and then consult the contents index that results. Example 116 (*): Vitrine An electrochromic window that becomes transparent or opaque depending on whether it is currently turned on. "Vitrine" Plaza View is a room. "Your uncle's apartment, on loan to you for viewing the parade and celebrations today. This would be more of a sacrifice on his part if he weren't currently yachting around Corfu." The smart window is a device in Plaza View. It is fixed in place. "A vast smart window [if transparent]overlooks the park[otherwise]has turned to a sheet of hazy blue[end if]." The smart window can be transparent. The smart window is transparent. The description is "An electrochromic device which changes shade and transparency in response to the application of current. Curtains are so last year." Note the "can be transparent" line. Devices ordinarily are not allowed to have transparency or opaqueness, but we can make an exception in this case. Without that line, attempts to change the transparency of the window will fail. Carry out switching off the window: now the window is transparent. Carry out switching on the window: now the window is opaque. Instead of searching a transparent window: say "Isn't it lovely out there?" Instead of searching an opaque window: say "The window is currently darkened." Test me with "look through window / switch window / look through window / look". Example 117 (*): Thirst A waterskin that is depleted as the player drinks from it. "Thirst" The player carries a waterskin. The waterskin can be full, partly drained, or empty. The waterskin is full. Understand "water" as the waterskin. Instead of drinking the waterskin when the waterskin is empty: say "There is no water left." Instead of drinking the waterskin: if the waterskin is partly drained, now the waterskin is empty; if the waterskin is full, now the waterskin is partly drained; say "You drink a long draught." After printing the name of the waterskin: say " ([waterskin condition])" Campsite is a room. "It is solid night now, and the stars have come out. Unfamiliar stars. On the other side of the valley -- a valley round-bottomed but shallow, like a soup bowl -- burn other campfires, most likely bandits. Their voices do not carry, but the smoke rises and obscures the starlight over that way." A sleepsack is an enterable container in the Campsite. "Your sleepsack is laid out in a pocket of sandy soil and coarse grass." The sandy soil, the stars, the distant campfires, and the coarse grass are scenery in the Campsite. Understand "smoke" as the campfires. Instead of listening in the presence of your campfire: say "All you hear are the reassuring snaps and cracks of the sticks in your fire." Understand "campfires" or "fires" as the distant campfires. Your campfire is scenery. Instead of pushing, pulling, turning, tasting, or touching your campfire, say "You would burn yourself." Understand "fire" as your campfire. The description of your campfire is "A reassuring protection against wild animals and cold." The description of the stars is "You invent constellations for them. The slingshot. The scroll. The heart (upside down)." Instead of going nowhere when the player is in Campsite: say "Now is not the time for wandering, alone in the dark. Better to keep here[if your campfire is visible], by the fire[end if]." Instead of singing: say "You sing, deep and low, a song from home. It is a good night for singing and the song raises your spirits." Test me with "i / drink water / i / drink water / i". Example 118 (*): Thirst 2 A campfire added to the camp site, which can be lit using tinder. "Thirst" The player carries a waterskin. The waterskin can be full, partly drained, or empty. The waterskin is full. Understand "water" as the waterskin. Instead of drinking the waterskin when the waterskin is empty: say "There is no water left." Instead of drinking the waterskin: if the waterskin is partly drained, now the waterskin is empty; if the waterskin is full, now the waterskin is partly drained; say "You drink a long draught." After printing the name of the waterskin: say " ([waterskin condition])" Campsite is a room. "It is solid night now, and the stars have come out. Unfamiliar stars. On the other side of the valley -- a valley round-bottomed but shallow, like a soup bowl -- burn other campfires, most likely bandits. Their voices do not carry, but the smoke rises and obscures the starlight over that way." A sleepsack is an enterable container in the Campsite. "Your sleepsack is laid out in a pocket of sandy soil and coarse grass." The sandy soil, the stars, the distant campfires, and the coarse grass are scenery in the Campsite. Understand "smoke" as the campfires. Instead of listening in the presence of your campfire: say "All you hear are the reassuring snaps and cracks of the sticks in your fire." Understand "campfires" or "fires" as the distant campfires. Your campfire is scenery. Instead of pushing, pulling, turning, tasting, or touching your campfire, say "You would burn yourself." Understand "fire" as your campfire. The description of your campfire is "A reassuring protection against wild animals and cold." The description of the stars is "You invent constellations for them. The slingshot. The scroll. The heart (upside down)." Instead of going nowhere when the player is in Campsite: say "Now is not the time for wandering, alone in the dark. Better to keep here[if your campfire is visible], by the fire[end if]." Instead of singing: say "You sing, deep and low, a song from home. It is a good night for singing and the song raises your spirits." The player carries a tinderbox. The tinderbox contains a flint, a steel, some tinder, and a patch of carbonized cloth. The description of the flint is "A flat grey stone with flaked edges." The description of the steel is "Curved so that you can hold it over the knuckles of your right hand and strike it against the flint. There is a knack to it. Those without the knack end up with bloody knuckles and no fire." The steel is wearable. The description of the tinder is "Dried grass and similar." The description of the cloth is "The little, precious, spark-preserving scraps without which the fire would never begin." Instead of attacking the flint when the steel is not worn by the player: say "You must wear the steel over your knuckles, in order to hit the flint at the best angle." Instead of attacking the flint when the steel is worn and the cloth is not in the location: say "Though you strike the flint sharply with the steel and throw sparks, they have nothing to catch on, since the patch of cloth does not lie beneath." Instead of attacking the flint when the steel is worn and the cloth is in the location and the cloth is not unlit: say "The patch of cloth has already caught." Instead of attacking the flint: now the cloth is glowing; say "You strike the flint against the steel and throw sparks onto the patch of cloth; they make tiny circles of orange there, which will only prosper if blown into flame." Realistically, we ought to attach a randomization to this so that each step of the fire-starting has a good chance of failure. But because our player may not be as patient as someone who actually needs a fire started, we allow him to succeed the first time in every case. Ignition is a kind of value. The ignitions are whole, fading, glowing, flaming. A thing has an ignition. Blowing on is an action applying to one thing. Understand "breathe on [something]" or "blow on [something]" as blowing on. Instead of blowing on the whole cloth: say "There is no point, since no sparks have caught there." Instead of blowing on the fading cloth: now the cloth is flaming; say "You blow on the faint sparks on the cloth and turn them into the beginnings of flame." Instead of burning the whole tinder: if the cloth is not flaming: say "The patch of cloth must catch flame before you can light anything with it."; otherwise: now the tinder is flaming; remove the cloth from play; say "You light the tinder with the patch of cloth, and have the elements of a fire." Every turn: unless the cloth is flaming or the cloth is whole: now the ignition of the cloth is the ignition before the ignition of the cloth; say "Now the patch of cloth is [ignition of the cloth]." Some kindling is in the campsite. Instead of burning the whole kindling: if the tinder is not flaming: say "You need the tinder to be flaming, first."; otherwise: remove the tinder from play; remove the kindling from play; move the campfire to the location; say "You succeed in lighting yourself a proper campfire."; now the printed name of Campsite is "By The Campfire". Test me with "i / drink water / i / drink water / i / wear steel / get flint / get cloth / drop cloth / get tinder / hit flint / blow on cloth / burn tinder / burn kindling / look". Example 119 (**): Meteoric I and II A meteor in the night sky which is visible from many rooms, so needs to be a backdrop, but which does not appear until 11:31 PM. The timing of the meteor's arrival uses features of Inform which the next chapter will go into at greater detail: suffice to say that the game below begins at half past eleven, and that one turn later is meteor time. "Meteoric I" The time of day is 11:30 PM. At 11:31 PM: move meteor to the great outdoors; say "A meteor streaks across the sky.". The great outdoors is a region. The Spanish Balcony is east of the Inner Court. The Court and Balcony are in the great outdoors. Inside from the Court is the Swimming Pool. The meteor is a backdrop. Instead of doing something to the meteor, say "The meteor is no longer visible, now nothing more than a memory." Test me with "wait / wait / examine meteor / west / examine meteor / in / examine meteor". Or for something a little slower-moving and with no after-image: "Meteoric II" The time of day is 4:30 PM. At 4:31 PM: move Phobos to the great outdoors; say "Phobos rises from the western horizon." At 10:06 PM: remove Phobos from play; say "Phobos sets over the eastern horizon." The great outdoors is a region. The Martian Balcony is east of the Inner Court. The Court and Balcony are in the great outdoors. Inside from the Court is the Heavy Water Swimming Pool. Phobos is a backdrop. Instead of doing something to Phobos, say "Phobos orbits a mere 6000km above you, which is practically touching range for astronomy. On the other hand, astronomy isn't all that practical." Test me with "wait / wait / examine phobos / west / examine phobos / in / examine phobos". Though we should not really use Earthly time-keeping, since the Martian day is about half an hour longer than ours. Example 120 (***): Orange Cones Creating a traffic backdrop that appears in all road rooms except the one in which the player has laid down orange cones. Because we can invent our own adjectives (see the chapter on Phrases), we can make the conditions for a backdrop as simple or as complicated as we like. In this scenario, we want the player to be able to take, move, and drop orange traffic cones to seal off one street or another. So we create our own "accessible" adjective as follows: Definition: a road is accessible if the orange cones are not in it. ...and now move the traffic backdrop to all accessible roads. will tell the traffic backdrop where to appear. "Orange Cones" A road is a kind of room. The traffic is a backdrop. It is not scenery. The initial appearance is "Dense traffic snarls the streets, making it difficult to cross even with the lights. Men on motorbikes edge between the cars, and sometimes pull up onto the sidewalks to go around." The description is "It is more or less as usual for this time of day. It's a wonder it ever dissipates, really." When play begins: move the traffic backdrop to all accessible roads. A line of orange cones are a thing. Definition: a road is accessible if the orange cones are not in it. After dropping the orange cones in a road: say "With steely determination you begin to lay out the orange cones, blocking access to this segment of street. This produces honking and swearing -- but you persevere."; update backdrop positions. After taking the orange cones: say "You go around taking up the orange cones, and within moments the traffic begins to flow into the street again."; update backdrop positions. That accomplishes everything we set out to do, but let's add a very simple puzzle to test it out with: The Town Square is a road. North of the Town Square is Candle Street. Candle Street is a road. East of Town Square is Mortar Street. Mortar Street is a road. The line of orange cones are in Mortar Street. The player wears a reflective vest and a hard hat. The manhole cover is a door. "[if location is accessible]Under the cars in the middle of the street, you can just make out the cover of the manhole you need to get into.[otherwise]There's a promising manhole in the middle of the street.[end if]". It is closed and openable. It is below the Town Square and above the Access Tunnel. Instead of opening the manhole cover when the location is an accessible road: say "You can't get anywhere near the manhole cover with all these cars above it." Instead of taking the orange cones in Town Square: if the manhole cover is closed or Town Square is accessible, continue the action; otherwise say "You'd better not let the traffic back in until you've closed the manhole. There'll be accidents otherwise." After going to the Access Tunnel: say "With a stealthy glance left and right, you lower yourself into the access tunnel, thus accomplishing your mission for Chapter 2. To continue your adventure, see Chapter 3: The Vault of Peaquod."; end the story finally. And finally, a couple of features from the Activities chapter to make the output more elegant: Rule for writing a paragraph about the orange cones: say "A line of orange cones holds back the traffic from entering here." Rule for printing the name of the orange cones when the cones are carried by the player: say "stack of orange cones". Test me with "x traffic / open manhole / n / x traffic / s / e / x traffic / get cones / look / x traffic / w / drop cones / look / open manhole / take cones / d". Example 121 (***): Terror of the Sierra Madre Multiple player characters who take turns controlling the action. Suppose we have a game where we want the player to control two different characters, swapping bodies from one turn to the next. First, the setting, and the two people who will alternately play: "Terror of the Sierra Madre" The Hay-Strewn Corridor is a room. "[if the player is Maleska]The horse stalls are empty: you have already drained the animals, and carried off their corpses. The house will not long sustain you now. The window throws on the floor a bright square of malevolent sunlight[otherwise]The stalls for horses run down one side of the room, but the house has long stood empty. A square window without shutters looks out over the ranch, away toward the Sierras[end if]." Teresa is a woman in the Hay-Strewn Corridor. "Teresa stands opposite you[if Teresa carries something], her fingers wrapped tightly around [a list of things carried by Teresa][end if]." Teresa carries a bulb of garlic and a cross. Maleska is a man in the Hay-Strewn Corridor. "Maleska watches you from eyes entirely black." Maleska carries a skull. If we tried the text above in Inform, we would find ourselves in the Hay-Strewn Corridor and confronted by both Teresa and Maleska. If "player" is not set to any named person, Inform creates a bland person called "yourself" to represent the player. To avoid this, we set "player" to the person we want to begin as: The player is Maleska. Now the Corridor contains just two people, and we arrive on the scene as Maleska, with only Teresa facing us. At the end of every turn we will use the 'change the player to...' phrase. (This looks as if it simply changes the value of "player": which it does, but it also carries out a complicated operation behind the scenes to effect the switch.) Every turn: if the player is Maleska, now the player is Teresa; otherwise now the player is Maleska. Our two characters already see the Corridor differently, but let's differentiate them further: Every person has a number called strength. The strength of Teresa is 3. The strength of Maleska is 5. In this small example, strength is not used for anything, except that we will display it on the status line: When play begins: now the command prompt is "[bold type][player][roman type] > "; now the left hand status line is "[player]"; now the right hand status line is "STR: [strength of the player]". That last rule doesn't quite do what we might have expected. When we print "[player]", we find that Inform usually prints "yourself". This is because Inform says "you" to mean Teresa when talking to the player-being-Teresa, and likewise for Maleska. We want to override that in this particular story, because the rapid switches of personality are otherwise hard to follow. So: Rule for printing the name of Teresa: say "Teresa". Rule for printing the name of Maleska: say "Maleska". Test me with "look / look". Example 122 (*): Beverage Service A potion that the player can drink. Some kinds of game objects -- food, for instance -- can only sensibly be used once, and should then be destroyed. The EAT command already implements this, but suppose we also had a category of drinkable potions: "Beverage Service" A potion is a kind of thing. The sparkly blue potion is a potion carried by the player. Level 3 is a room. Instead of drinking a potion: remove the noun from play; say "You quaff [the noun]. It goes down beautifully." Test me with "drink sparkly / i". Example 123 (*): Spring Cleaning A character who sulks over objects that the player has broken (and which are now off-stage). Here we have a destruction action that allows the player to break any fragile items. Once destroyed, these things are removed from play, but we can still refer to them: they are now off-stage. This makes it easy for our sulking character to list the ones that have been destroyed: "Spring Cleaning" A thing can be tough or fragile. A thing is usually tough. Instead of attacking something fragile: say "You smash [the noun] to smithereens!"; remove the noun from play. A knick-knack is a kind of thing which is fragile. Every turn when a knick-knack is off-stage and Granny Blue can see the player: say "'Ohh,' whimpers Granny to herself softly. 'How I will miss [the list of off-stage knick-knacks]!'" The Parlor is a room. Granny Blue is a woman in the Parlor. A china lamb, a porcelain milkmaid, a frolicking Dutch cow, and a crystal unicorn are knick-knacks in the Parlor. Test me with "break lamb / break milkmaid / break cow / break unicorn". Example 124 (**): Extra Supplies A supply of red pens from which the player can take another pen only if he doesn't already have one somewhere in the game world. Suppose we have a supply closet in our game from which the player is allowed to take red pens. To keep modeling simple, we only allow him to have one in play at a time, and we test this by seeing whether the red pen is "off-stage" before moving it to his possession. This approach might seem no different from having a single red pen sitting in the closet, but it may be preferable, for two reasons. First, it's not very plausible for a supply closet to contain nothing but a single red pen (well, assuming a well-regulated supplier, anyway); and second, it gives the player a way to get a new red pen should the original be destroyed in a tragic handwriting accident. "Extra Supplies" The Supply Closet is a room. A supply of red pens is in the Supply Closet. Understand "pen" as the supply of red pens when the red pen is not visible. There is a red pen. Instead of taking the supply of red pens: if the red pen is off-stage: move the red pen to the player; say "You help yourself to a fresh red pen."; otherwise: say "You're only allowed one pen at a time. The department secretary is very strict." South of the Supply Closet is the Furnace Room. The incinerator is a thing in the Furnace Room. It is a container. "The incinerator is here, working full blast." After inserting something into the incinerator: remove the noun from play; say "A fiery blast consumes [the noun]!" Test me with "get pen / i / get pen / get supply / s / put pen in incinerator / n / get pen". Example 125 (*): Bee Chambers A maze with directions between rooms randomized at the start of play. Mazes are a traditional element of interactive fiction, often consisting of apparently identical rooms with exits that do not work reciprocally and which cause confusion. The methods of mapping mazes are now fairly well understood and mazes themselves tend to be regarded as tiresome rather than enjoyable by a large portion of the playing audience. However, if we did want to ignore the common wisdom and create a maze, randomly generated at the start of play, here would be one way to go about it: "Maze of Gloom" A Bee Chamber is a kind of room. The printed name of a Bee Chamber is usually "Hexagonal Room". The description of a Bee Chamber is usually "Waxy, translucent walls surround you on six sides; the floor and ceiling are made of the same material, gently uneven. There are exits in every direction, cut into the faces or the corners." Bee1, Bee2, Bee3, Bee4, Bee5, Bee6, Bee7, Bee8, Bee9, and Bee10 are Bee Chambers. When play begins: now right hand status line is "[number of visited rooms]/[number of rooms]"; repeat with place running through Bee Chambers: now a random Bee Chamber is mapped north of place; now a random Bee Chamber is mapped northwest of place; now a random Bee Chamber is mapped west of place; now a random Bee Chamber is mapped southwest of place; now a random Bee Chamber is mapped south of place; now a random Bee Chamber is mapped southeast of place; now a random Bee Chamber is mapped east of place; now a random Bee Chamber is mapped northeast of place; now a random Bee Chamber is mapped above place; now a random Bee Chamber is mapped below place; now a random Bee Chamber is mapped inside place; now a random Bee Chamber is mapped outside place. Test me with "in / out / up / down / n / ne / nw / e / w / sw / se / s". Example 126 (**): Hatless It's tempting to use "now..." to distribute items randomly at the start of play, but we need to be a little cautious about how we do that. Suppose we want a game in which each scenario starts with the characters wearing hats -- randomly passed out. We might be tempted to write our scenario like this: "Hatless" The Costumery is a room. Larry, Curly, and Moe are men in the Costumery. Janine is a woman in the Costumery. Rule for writing a paragraph about a person (called the target) who wears a hat (called attire): say "[The target] is here, looking stylish in [an attire]." Rule for writing a paragraph about a hatless person (called the target): say "[The target] mopes about, hatless." A hat is a kind of thing. A hat is always wearable. Definition: a person is hatless if he does not wear a hat. The indigo bowler, the polka-dotted fedora, the pink beret, and the scarlet cloche are hats. When play begins: now every hat is worn by a random hatless person. And we might hope that this would choose a new hatless person for each hat, but we would be wrong. It will instead choose one hatless person and put all the hats on him -- and everyone else has to go bare-headed. That's clearly no good. Let's try again: "Hatless 2" The Costumery is a room. Larry, Curly, and Moe are men in the Costumery. Janine is a woman in the Costumery. Rule for writing a paragraph about a person (called the target) who wears a hat (called attire): say "[The target] is here, looking stylish in [an attire]." Rule for writing a paragraph about a hatless person (called the target): say "[The target] mopes about, hatless." A hat is a kind of thing. A hat is always wearable. Definition: a person is hatless if he does not wear a hat. The indigo bowler, the polka-dotted fedora, the pink beret, and the scarlet cloche are hats. When play begins: now every hatless person wears a random hat. But this selects one random hat and assigns it to each hatless person in turn -- so it will only wind up being worn by the last of them (since Inform knows that only one person can wear a hat at a time). In this case, we do have to expand out our loop so that the game makes an explicit distribution: "Hatless 3" The Costumery is a room. Larry, Curly, and Moe are men in the Costumery. Janine is a woman in the Costumery. Rule for writing a paragraph about a person (called the target) who wears a hat (called attire): say "[The target] is here, looking stylish in [an attire]." Rule for writing a paragraph about a hatless person (called the target): say "[The target] mopes about, hatless." A hat is a kind of thing. A hat is always wearable. Definition: a person is hatless if he does not wear a hat. The indigo bowler, the polka-dotted fedora, the pink beret, and the scarlet cloche are hats. When play begins: repeat with item running through hats: now the item is worn by a random hatless person. Each time Inform considers the instruction "now the item is worn by a random hatless person", there is one fewer such person to choose from -- so we can guarantee that the hats are distributed one per customer and that all hats are distributed. Hatless 3 is only guaranteed to work because the number of hats is less than or equal to the number of people; otherwise the final use of random will return "nothing" and then a problem message will appear during play. Example 127 (***): Technological Terror A ray gun which destroys objects, leaving their component parts behind. "Technological Terror" The Decomposition Ray Gun is a thing carried by the player. First we need to define our shooting action: Shooting it with is an action applying to two things. Check shooting something with something: if the player is not carrying the Ray Gun, say "You are pathetically unarmed!" instead; if the second noun is not the Ray Gun, say "[The second noun] does not fire." instead; if the noun is the Ray Gun, say "Nice trick if you can do it!" instead; if the noun is the player, say "That would be disastrous!" instead. Next, some grammar to allow the player to use this action: Understand "shoot [gun] at [something ungunlike]" as shooting it with (with nouns reversed). Definition: a thing is ungunlike if it is not the gun. Understand "shoot [something ungunlike] with [gun]" as shooting it with. Understand "shoot [something] with [something]" as shooting it with. Understand "shoot [something] at [something]" as shooting it with (with nouns reversed). Understand "fire [gun] at [something ungunlike]" as shooting it with (with nouns reversed). Understand "fire at [something ungunlike] with [gun]" as shooting it with. Understand "fire at [something] with [something]" as shooting it with. Strictly speaking, we only need these last grammar lines (with "understand shoot something...") in order to define an action that the player can take. Adding more grammar lines means that Inform will try to match the most specific ones first, which is useful when the player types something ambiguous and there is one choice that obviously fits this action better than the others. See the chapter on Understanding for a further discussion. Here we get to use "now..." to give it its destructive effect: Carry out shooting something with something: say "ZAP! [The noun] twinkles out of existence! [if something is part of the noun][The list of things which are part of the noun] clatter to the ground! [end if][paragraph break]"; now every thing which is part of the noun is in the location; remove the noun from play. The Deathbot Assembly Line is a room. "Here is the heart of the whole operation, where your opponents are assembled fresh from scrap metal and bits of old car." The dangerous robot is a thing in the Assembly Line. "One dangerous robot looks ready to take you on!" A robotic head, a drill arm, a needle arm, a crushing leg and a kicking leg are parts of the dangerous robot. Instead of examining something when something is part of the noun: say "[The noun] consists of [a list of things which are part of the noun]." Test me with "x robot / shoot robot / fire at kicking leg / shoot gun at drill arm / look". Example 128 (*): Higher Calling All doors in the game automatically attempt to open if the player approaches them when they are closed. "Called" is quite useful in the context of rules about going, since go rules often refer to things other than the noun the player typed. For instance, suppose we want to have doors which politely open when the player tries to pass through them: "Higher Calling" Before going through a closed door (called the blocking door): say "(first opening [the blocking door])[line break]"; silently try opening the blocking door; if the blocking door is closed, stop the action. Dome is a room. North of Dome is North Chapel. South of the Dome is South Chapel. West of the Dome is Western End. Quiet Corner is northwest of the Dome, north of Western End, and west of North Chapel. Loud Corner is east of North Chapel, northeast of Dome, and north of Eastern End. Eastern End is north of Dim Corner and east of Dome. Dim Corner is southeast of Dome and east of South Chapel. Ruined Corner is southwest of Dome, west of South Chapel, and south of Western End. The church door is east of Eastern End and west of the Courtyard. The church door is a door. Test me with "e / e". A fuller set of such rules is included in the Locksmith extension. Example 129 (*): Do Pass Go A pair of dice which can be rolled, and are described with their current total when not carried, and have individual scores when examined. "Do Pass Go" Go is a room. "A giant square area, where you and your other pewter ornament friends gather before setting out to purchase London." The pair of dice is carried by the player. The pair of dice has a number called first die. The pair of dice has a number called second die. The first die of the pair is 6. The second die of the pair is 6. Rule for printing the name of the pair of dice while taking inventory: say "pair of dice". Rule for printing the name of the pair of dice: say "pair of dice showing [first die of the pair plus second die of the pair]". To say detailed state of the dice: if the first die of the pair is the second die of the pair, say "double [first die of the pair]"; otherwise say "[first die of the pair] and [second die of the pair]". The description of the pair of dice is "The pair of dice are [if the dice are carried]itching to be rolled[otherwise]showing [detailed state of the dice][end if]." Rolling is an action applying to one carried thing. Understand "roll [something preferably held]" as rolling. Check rolling when the noun is not the pair of dice: say "Not something you can roll." instead. Carry out rolling: now the pair of dice is in the holder of the actor; now the first die of the pair of dice is a random number from 1 to 6; now the second die of the pair of dice is a random number from 1 to 6. Report rolling: say "You roll [detailed state of the dice]." Test me with "i / roll dice / look / x dice / get dice / x dice / roll dice / roll dice / roll dice / roll dice / roll dice / roll dice / roll dice". Because we remember the states of the individual dice, not just a total, we can make use of the combination rolled. The doubles count is a number that varies. After rolling: if the first die of the pair is the second die of the pair, increment the doubles count; otherwise now the doubles count is 0; continue the action. Jail is a room. "This is Jail, and not the Just Visiting periphery, either." Every turn when the doubles count is 3: say "The blue-uniformed policemen blows his whistle and beckons you sternly..."; now the player carries the pair of dice; now the player is in Jail; now the doubles count is 0. Every turn when the doubles count is 1 and the player is in Jail: say "The warden gruffly releases you."; now the player carries the pair of dice; now the player is in Go. Example 130 (*): Lanista 1 Very simple randomized combat in which characters hit one another for a randomized amount of damage. "Lanista, Part One" The Arena is a room. "Sand, blood, iron. These festivals are normally held on hot days, but the sun has gone behind a cloud and fat drops of rain now and then spatter the arena floor." The gladiator is a man in the Arena. "A bare-chested Scythian gladiator faces you, wielding a trident." We start by recording, for each person, a maximum number of points of damage the person can sustain when starting from health, and the current number of points remaining. In the tradition of role-playing games, these are referred to as hit points. A person has a number called maximum hit points. A person has a number called current hit points. The maximum hit points of the player is 35. The maximum hit points of the gladiator is 25. The current hit points of the player is 35. The current hit points of the gladiator is 25. Now our rule for the actual attack. We want first to calculate how much damage the player's attack does, inflict that damage, and remove the enemy if he's dead; then, if he doesn't die, the enemy counter-attacks, also for a randomized amount of damage, and if this kills the player, the game ends in defeat. Instead of attacking someone: let the damage be a random number between 2 and 10; say "You attack [the noun], causing [damage] points of damage!"; decrease the current hit points of the noun by the damage; if the current hit points of the noun is less than 0: say "[line break][The noun] expires, and is immediately carried away by the Arena slaves!"; remove the noun from play; end the story finally; stop the action; let the enemy damage be a random number between 2 and 10; say "[line break][The noun] attacks you, causing [enemy damage] points of damage!"; decrease the current hit points of the player by the enemy damage; if the current hit points of the player is less than 0: say "[line break]You expire!"; end the story. This last bit is a refinement to help the player keep track of how the contest is going: When play begins: now the left hand status line is "You: [current hit points of player]"; now the right hand status line is "Gladiator: [current hit points of gladiator]". Test me with "hit gladiator / g / g / g". Example 131 (*): Weathering The automatic weather station atop Mt. Pisgah shows randomly fluctuating temperature, pressure and cloud cover. "Weathering" A cloud pattern is a kind of value. The cloud patterns are cumulus, altocumulus, cumulonimbus, stratus, cirrus, nimbus, nimbostratus. The Mount Pisgah Station is a room. "The rocky peak of Mt. Pisgah (altitude 872m) is graced only by an automatic weather station. The clouds, close enough almost to touch, are [a random cloud pattern]. Temperature: [a random number from 7 to 17] degrees, barometric pressure: [950 + a random number from 0 to 15] millibars." Test me with "look / look / look". Example 132 (***): Uptown Girls A stream of random pedestrians who go by the player. Suppose we have an urban space we want to populate with random passers-by. These should have a range of characteristics and not always be described in the same way; and once the player has noticed one, he should be able to look at her further, until another pedestrian crosses his path. "Uptown Girls" Riverside Drive is a room. "There's a pleasant late-afternoon view of the Hudson, and a snap in the air, and you would rather be here than anywhere." Instead of going a direction, say "Oh, you know where you're going; no need to deviate from the usual path." Instead of waiting, say "You stroll along enjoying the November crispness." It gets a little annoying to have a random event occurring every single turn of play, so let's introduce some randomness to determine how often the message appears: Every turn when a random chance of 1 in 3 succeeds: reset passerby; choose a random row in the Table of Atmospheric Events; say "[event entry][paragraph break]" Table of Atmospheric Events event "Slowly [a passerby] strolls by, turning to look at you as she passes." "Some [passerby] nearly bumps into you." "You dodge to avoid [a passerby]." "You weave around [a passerby], who has stalled to look into a window." "There's a ruckus as one of the ubiquitous taxis nearly collides with [a passerby] crossing the street." "[The passerby] beside you waves to a friend across the street." "To your left, [a passerby] drops her purse, and swears as she retrieves it." Hair color is a kind of value. A person has hair color. the hair colors are red-headed, brunette, blonde. Height is a kind of value. A person has height. The heights are tall, medium-height, short. Grooming is a kind of value. A person has grooming. The groomings are messy and tidy. To reset passerby: now the hair color of the passerby is a random hair color; now the height of the passerby is a random height; now the grooming of the passerby is a random grooming. The passerby is a woman in Riverside Drive. The passerby is scenery. Understand "woman" or "lady" as the passerby. The printed name of the passerby is "[one of]woman[or]lady[purely at random]". At this point we borrow some techniques from later to describe the woman with a random combination of characteristics, and to let the player refer to her by those traits: Before printing the name of the passerby: if a random chance of 1 in 4 succeeds, say "[height] "; if a random chance of 1 in 4 succeeds, say "[grooming] "; if a random chance of 1 in 4 succeeds, say "[hair color] ". Understand the hair color property as describing the passerby. Understand the height property as describing the passerby. Understand the grooming property as describing the passerby. If we also wanted each of those combinations to mean some more specifically-described woman: Instead of examining a passerby: repeat through Table of Passerby Descriptions: if hair entry is the hair color of the passerby and height entry is the height of the passerby and grooming entry is the grooming of the passerby, say "[description entry][paragraph break]". Table of Passerby Descriptions hair height grooming description red-headed tall messy "An older woman with long red hippie-hair poking out of a ponytail in straggles, and bent to hide how tall she is." red-headed medium-height messy "A shaggy red-head with shingled hair." red-headed short messy "Almost an urchin, and very young, with ginger hair and a smudged nose and far too many freckles." red-headed tall tidy "A precise career woman with henna-red hair." red-headed medium-height tidy "Her hair is red in the way that lollipops and fire trucks are red: not by nature but by art. The rest of her clothing is pretty ordinary, though." red-headed short tidy "Thin and small in every sense, with chin-length red-hair. Even high heels do not bring her head much above your shoulder." brunette tall messy "A Juno-esque woman with dark hair, wearing something resembling a tent." brunette medium-height messy "An unremarkable woman with dark brown hair and the aura of needing a wash." brunette short messy "There are mustard stains on the t-shirt of this short brown-haired woman. Estimated age ca. 40. Possibly homeless." brunette tall tidy "A leggy brunette in business attire." brunette medium-height tidy "Medium-height, brown-haired, generally nondescript." brunette short tidy "A neat little dark-haired girl." blonde tall messy "A tall blonde of about thirteen who looks as though she has not yet figured out how to get her wardrobe to catch up with her rate of growth. Her t-shirt and her pants are too short." blonde medium-height messy "Black leather pants and the wall-o-hair look." blonde short messy "One of those shocking platinum blonde types, with a tiger-patterned skirt. Reeally trashy." blonde tall tidy "Elfin and severe, with perfectly straight hair falling to the middle of the back." blonde medium-height tidy "A rounded, Marilyn-esque blonde." blonde short tidy "Pin-precise in a blue-and-white striped suit and a boyish haircut." Test me with "z / z / x passerby / z / z / x passerby". Example 133 (*): Candy One of several identical candies chosen at the start of play to be poisonous. Suppose we want to give the player a bag of candies, of which a random one is poisonous. We can pick which one should be poisoned at the start of play, like this: "Candy" The plural of piece of candy is pieces of candy. A piece of candy is a kind of thing. A piece of candy is always edible. Four pieces of candy are in the Halloween bag. Toxicity is a kind of value. The toxicities are safe and poisonous. A piece of candy has a toxicity. A piece of candy is usually safe. The Porch is a room. The player carries the Halloween bag. After eating a poisonous piece of candy: say "Oh, that didn't taste right at all. Oh well!" When play begins: now a random piece of candy is poisonous. Test me with "eat candy / g / g / g". Example 134 (*): Zork II A "Carousel Room", as in Zork II, where moving in any direction from the room leads (at random) to one of the eight rooms nearby. All we need to do is select the player's destination for him at random: "Zork II" The Carousel Room is a room. Instead of going from the Carousel Room: move the player to a random adjacent room. To avoid infringing the original game too much, let's try a somewhat different setting: The Games of Chance is north of the Carousel Room. The Haunted Funhouse is northwest of the Carousel Room. The Ferris Wheel is east of the Carousel Room. The Topsy-Turvy is northeast of the Carousel Room. The Reproduction Henge is south of the Carousel Room. The Women's Toilet is southwest of the Carousel Room. The Men's Toilet is southeast of the Carousel Room. The Cotton Candy Shop is west of the Carousel Room. Test me with "s". And the following means that the test runs consistently even though the numbers are theoretically random. To make them truly random, remove this line. When play begins, seed the random-number generator with 1234. Or if we want to add the refinement that the Carousel Room can be switched off: "Zork II" The Carousel Room is a room. The spinning machine is a switched on device in the Carousel Room. And then Instead of going from the Carousel Room when the spinning machine is switched on: move the player to a random adjacent room. The Games of Chance is north of the Carousel Room. The Haunted Funhouse is northwest of the Carousel Room. The Ferris Wheel is east of the Carousel Room. The Topsy-Turvy is northeast of the Carousel Room. The Reproduction Henge is south of the Carousel Room. The Women's Toilet is southwest of the Carousel Room. The Men's Toilet is southeast of the Carousel Room. The Cotton Candy Shop is west of the Carousel Room. Test me with "turn off machine / s / n / turn on machine / s". When play begins, seed the random-number generator with 1234. Example 135 (*): Clueless A murderer for the mystery is selected randomly at the beginning of the game. "When play begins" is the best point to initialize any aspects of the game that are meant to change between playings. For instance, in this scenario, we would randomly select one of the other characters to be guilty of murder: "Clueless" The murderer is a person that varies. When play begins: now the murderer is a random person who is not the player. The Billiards Room is a room. Colonel Mustard and Professor Plum are men in the Billiards Room. Miss Scarlet and Mrs White are women in the Billiards Room. Instead of examining the murderer: say "[The noun] certainly looks fiendish!" Test me with "x mustard / x plum / x scarlet / x white". Example 136 (**): Mutt's Adventure Awarding points for visiting a room for the first time. Suppose we want to reward the player the first time he reaches a given room. The "unvisited" attribute is useful for this: unlike such constructions as "going to a room for the first time", it doesn't develop false positives when the player has merely tried to go to the room in question. "Every turn when the player is in a room for the first time" is also unhelpful, because it continues to be true as long as the player is in a room on his first visit there. "Mutt's Adventure" Section 1 - Procedure A room can be scored or unscored. Carry out going to a unvisited scored room: increment the score. Section 2 - Scenario The Incan Palace Compound is a room. "After numerous false leads through the jungles of Peru, and an arduous trek along the Amazon, you have arrived, at last, here: at Atagon, the lost city of untold treasure." The startlingly intricate door is a door. It is inside from Incan Palace Compound and outside from the Treasure Room. "A door carved all over with figures of ancient gods, and protected by an assortment of gears and latches, [if open]stands open[otherwise]blocks progress[end if] towards [the other side of the intricate door]." The description of the Treasure Room is "To your considerable surprise, the treasure room is stocked with art objects from a vast range of eras and geographical locations: beside the expected pre-Columbian gold there are Cycladic figurines, Chinese Tang-dynasty pottery, purses that might have been stolen from Sutton Hoo. [one of]If the British Museum developed a nasty expectorant cough, this is what you'd find in its hanky.[or][stopping]". The Treasure Room is scored. Test me with "in / out / in". Example 137 (***): No Place Like Home Recording a whole table of scores for specific treasures. Suppose we want to assign scores for a whole range of objects the player might pick up. One systematic way to do this would be with a table of point values for things: "No Place Like Home" The Hall of the Gnome King is a room. The emerald cow is a thing in the Hall of the Gnome King. The ivory chessman is a thing in the Hall of the Gnome King. The book of incantations is a thing in the Hall of the Gnome King. Table of Point Values item score cow 10 incantations 4 chessman 1 Report taking an item listed in the Table of Point Values: increase the score by the score entry; blank out the whole row. Test me with "take all". "Blank out the whole row" removes the line from the table, so that each award will occur only once. The player will not be able to earn more and more points by dropping and taking the same item again. Example 138 (***): Big Sky Country Allowing the player to continue play after a fatal accident, but penalizing him by scattering his possessions around the game map. Some older games allowed the player to be resurrected after a death, but punished him by distributing his possessions far and wide. Here we emulate that effect. "Big Sky Country" When play begins: say "There's a bit of a drive over from Anaconda, Montana, and then through a couple or three ghost towns, but finally you find what you're looking for, and strike out on foot..." Entrance to Devil's Canyon is a room. "You are at the top of a steep road, which proceeds down into the canyon proper." A sign is in Devil's Canyon. It is fixed in place. "An ominous sign has been put up by the local sheriff's office." The description is "PROCEED AT OWN RISK - NO RESCUES!" Instead of going down when a random chance of 1 in 3 succeeds: say "Whoooops, your footing is not as secure as you thought..."; end the story. Dusty Path is below Entrance. "A dusty path, with grey-brown thorny bushes on either side. Immediately to your right is a sheer drop; far below you can see the rusting remains of a Model T that some fool tried to drive by here." Hairpin is below Dusty Path. "A sharp bend in the road, doubling back down towards the bottom of the canyon. Just north of here there is also a small cavern of some kind[if the stick pin is in the cavern], which attracts your eye with some glittery thing[end if]." The Cavern is north of Hairpin. "Really not much more than a little hollow in the side of the canyon." In the cavern are a snake and a diamond stick pin. The snake is an animal. The description of the snake is "You're no expert, but it looks like a rattler." Instead of taking the diamond stick pin in the presence of the snake: say "Turns out the snake is partial to that there pin, and takes exception to your intending to make off with it."; end the story. In a fuller implementation of this game, we might make it possible to get by the snake, but in this version, it's just going to remain troublesome. Crooked Path is below Hairpin. "You're about two thirds of the way down to the bottom of the cavern at this point." At the Spot is below Crooked Path. "This'll be it: a bare patch of ground that might as well have an X painted right on it." Rule for supplying a missing noun while digging: now noun is the location. Understand "dig" or "dig hole/here" or "dig in ground/dirt/earth" as digging. Digging is an action applying to one thing. Instead of digging at the spot: say "You dig and dig, and after a half hour or so, sure enough, you do turn up a big box of gold! You're going to be richer than God and Bill Gates put together."; increase the score by 5; end the story finally. Instead of digging at the spot when the player does not carry the shovel: say "What, without your shovel? That won't work too well." The player carries a walking stick. The player wears a hat, a whistle, and a daypack. The daypack contains a mylar blanket, a granola bar, a cellular phone, a water bottle, a folding shovel, and a photocopied map. The granola bar is edible. Instead of drinking the water, say "You quench your thirst, for the time being." The description of the map is "The map shows the winding path of Devil's Canyon, with a large X down by the south end. That would be where your uncle Jesse buried the gold from the train robbery." The maximum score is 5. When play ends when the story has not ended finally: say "Oh dear, that ought to be fatal! However, if you like I can get you out of it... Shall I? >"; if the player consents: repeat with item running through things had by the player: move the item to a random visited room; say "A strong wind picks you up and sets you back at [the location], though perhaps minus a few of your things."; resume the story; try looking. "If the player consents" is just a convenient way to ask a yes/no question that the player must answer before going on with the game. Example 139 (***): Witnessed 1 A kind of battery which can be put into different devices, and which will lose power after extended use. The following example makes fairly ample use of material that we haven't seen yet, but gives some idea of the flexibility of every turn rules. Suppose we want to have a number of electrical devices, all of which may be powered by a set of batteries. The batteries will all need to be discharged as they are used (regardless of what device they happen to be controlling at the moment). So: "Witnessed" A battery is a kind of thing. A battery has a number called charge. The charge of a battery is usually 15. Every turn: repeat with hollow running through battery compartments: if the hollow is part of a switched on device (called the machine): if a battery (called cell) is in the hollow: decrement the charge of the cell; carry out the warning about failure activity with the machine; if the cell is discharged, carry out the putting out activity with the machine; otherwise: carry out the putting out activity with the machine. Warning about failure of something is an activity. Rule for warning about failure of a device (called the machine): if a random battery compartment which is part of the machine contains a battery (called the power source): if the charge of the power source is 2, say "[The machine] is obviously going to go out quite soon." Putting out something is an activity. Rule for putting out a device (called the machine): say "[The machine] loses power and switches off![line break]"; silently try switching off the machine. A battery compartment is a kind of container. A battery compartment is usually closed and openable. One battery compartment is part of every device. Instead of inserting something which is not a battery into a battery compartment, say "Only batteries should go in a battery compartment." And to get rid of annoying messages like "Which would you like to close, the flashlight or the flashlight's battery compartment?" when only the compartment is closable, we might add some understanding instructions: Understand "turn on [device]" as switching on. Understand "turn off [device]" as switching off. Understand "open [openable closed thing]" as opening. Understand "close [openable open thing]" as closing. Understand "put [something] in [container]" as inserting it into. Instead of opening a device, try opening a random battery compartment which is part of the noun. Instead of closing a device, try closing a random battery compartment which is part of the noun. Instead of inserting a battery into a device, try inserting the noun into a random battery compartment which is part of the second noun. Instead of switching on an empty device: say "Nothing happens, perhaps because there isn't a charged battery in [the noun]." Instead of switching on a battery compartment which is part of a device (called the power user), try switching on the power user. Definition: a device is empty: if a random battery compartment which is part of it contains a battery (called the power source): if the power source is discharged, yes; no; yes. Definition: a battery is discharged if its charge < 1. A light source is a kind of device. Carry out switching on a light source: now the noun is lit. Carry out switching off a light source: now the noun is unlit. The flashlight is a light source. A D battery is a battery carried by the player. The cassette recorder is a device. Every turn: if the cassette recorder is switched on, say "The cassette recorder hisses faintly." Rule for warning about failure of the cassette recorder: if a random battery compartment which is part of the cassette recorder contains a battery (called the power source): if the charge of the power source is 2, say "The hiss from [the cassette recorder] begins to warble ominously." The player wears a backpack. The backpack is openable. In the backpack is the flashlight and the cassette recorder. The description of the cassette recorder is "Useful both for recording your notes and for capturing any odd ghostly sounds you may hear." The description of the backpack is "An old familiar pack, which you know so well that you can find all its pockets and take things in and out of it in pitch darkness. To avoid it showing up oddly in photographs, it is entirely black, with no shiny or metallic attachments." The description of the flashlight is "You bought a new one just for this occasion, because you were worried about bringing something too small or light. This is a heavy-duty flashlight with an adjustable-focus beam. The case is made of metal, rather than plastic, and there is a spare light-bulb inside as well. You've put a band of masking tape around the handle and written in your initials in red marker. There is a piece of red cellophane attached to the business end of the flashlight to keep it from being overly bright." The red cellophane is part of the flashlight. Instead of doing something to the red cellophane: say "You need the cellophane on the flashlight so that using it does not completely destroy your night vision." Thirtieth Street Station is a room. "A huge, high, rectangular room with coffered ceilings, which looks grand but mostly makes you feel lonely and small. There are long benches in rows down the middle of the room, and an information desk with the train times, and a series of ticket windows, none of which matters very much at the moment." The benches are an enterable supporter. They are scenery in the Station. The information desk is scenery in the Station. Some ticket windows are scenery in the Station. Instead of examining scenery in the Station: say "You're fairly sure that whatever is going on here has nothing to do with [the noun]." Understand "window" as ticket windows. The mural is fixed in place in Thirtieth Street. "At the north side of the station is a particularly pointless and empty annex to the main room. It is dominated by a huge relief of sorts, and this is what you remember." Understand "metal" or "relief" or "huge" as the mural. The description of the mural is "It is both stylized and confusing, but you think it might be supposed to represent the various tasks and occupations of Philadelphia's population. The portions closer to the ground look as though they have recently been subjected to a light dusting of talcum powder. No unusual prints are evident." The wind chimes are fixed in place in Thirtieth Street. "Carefully attached to the wall with a piece of duct tape and a hook is a light-weight set of wind chimes. Someone else has been here before you, it seems." The description is "Several of your friends use wind chimes as a sort of ghost alarm, since ghosts sometimes cause very localized movements of air when there is no natural breeze." And this last bit, borrowed from the chapter on Understanding, adds some special instructions to help Inform decide when the player is likely to be referring to a compartment and when he's likely to be referring to the device itself. Does the player mean doing something other than searching to a battery compartment: it is unlikely. [We discourage Inform from choosing a compartment when the player uses just the name of a device or the word 'battery'.] We also need to deal with commands like PUT BATTERY IN FLASHLIGHT, where Inform might construe BATTERY as the D battery, the flashlight's battery compartment, or the cassette recorder's battery compartment -- and might also construe FLASHLIGHT as either the flashlight's battery compartment or the flashlight itself. Does the player mean inserting into a battery compartment: if the noun is nothing: it is very likely; otherwise: make no decision. Does the player mean inserting a battery compartment into: it is very unlikely. Does the player mean inserting something into a device: it is unlikely. Does the player mean searching a battery compartment: it is very likely. Test me with "test first / test second". Test first with "i / open flashlight compartment / put battery in it / turn on flashlight / take d battery / open cassette compartment / turn on cassette / put battery in cassette compartment / turn on cassette / z / z / z / z". Test second with "get d battery / put d battery in flashlight compartment / turn on flashlight / z / z / z / z / z / z / turn off flashlight / z / z / turn on flashlight / z". Example 140 (****): Text Foosball A game of foosball which relies heavily on every-turn rules. Suppose we want a game of foosball in which our opponent acts every turn, but does different things depending on where the ball currently lies. We can put together a sequence of every-turn rules to account for this, as follows: "Text Foosball" The Lounge is a room. "The Lounge is appointed with everything necessary to rest and relaxation: a vending machine, a potted palm, a stack of Entertainment Weekly issues from 1993, and -- your pride and joy -- a foosball game." The foosball game is scenery in the Lounge. Understand "table" or "football" or "foozball" or "fussball" or "soccer" as the foosball game. The game is a supporter. On the game is a small white ball. The ball can be still, approaching, receding, or unreachable. The description of the ball is "Currently [small white ball condition]." After printing the name of the small white ball, say " ([small white ball condition])". When play begins: now left hand status line is "You: [score]"; now right hand status line is "Joey: [Joey's score]". Some tiny men on sticks are part of the game. Understand "handles" as the tiny men. The description is "Okay, a couple of the tiny men have had their feet broken off, and the table surface itself is a bit warped, and the ball resembles a quail egg in respect of shape and color. This makes for a game of unusual randomness, but skill is overrated." Instead of attacking or pulling or pushing the game when the ball is unreachable: say "You give the table a good shove, and the ball moves ever-so-slightly."; now the ball is still. Instead of taking the white ball: say "You'd forfeit the game if you did that." Instead of turning the tiny men when the ball is unreachable: say "The ball has somehow gotten to a mystical point on the table where it cannot be reached, no matter what. Close inspection reveals that this point has been marked in chalk with a tiny X. Not that that does any good." Instead of turning the tiny men when the ball is approaching: if a random chance of 2 in 3 succeeds: if a random chance of 1 in 2 succeeds, now the ball is receding; otherwise now the ball is still; say "[if the ball is still]Thunk. [otherwise]Thwack! [end if]You keep the ball from reaching its goal! Now it is [small white ball condition]."; otherwise: let Joey score. To let Joey score: now the ball is still; now Joey's score is Joey's score + 1; say "The ball rolls neatly into your goal, despite your efforts. "; if Joey's score < score, say "You put the ball back in the center with a snap. No reason to worry yet; you're still ahead. Joey looks determined, though."; otherwise say "After allowing a moment or two for Joey's gloating to pass, you replace it at the center." Instead of turning the tiny men when a random chance of 1 in 13 succeeds: if the ball is unreachable, continue the action; now the ball is unreachable; say "You hit the ball off-center and it rolls sluggishly into a little dip in the surface of the foosball table. "; if Joey's score > 7, say "'You did that on purpose!' Joey exclaims indignantly."; otherwise say "You and Joey exchange glances. This is never good." Instead of turning the tiny men: say "You madly rotate the tiny men on sticks! "; if a random chance of 1 in 2 succeeds: say "Hoorah! You hit the ball!"; now the ball is receding; otherwise: say "Somehow you fail to bring your monopodal player into contact with the ball." Joey is a man in the Lounge. "Joey is hunkered over the foosball handles on his side of the table." Joey can be active or inactive. Joey's score is a number that varies. Every turn: now Joey is active. Every turn when the ball is approaching and Joey is active: let total be Joey's score + score; if total > 9, make no decision; now Joey is inactive; let Joey score; rule succeeds. Every turn when the ball is unreachable and Joey is active: let total be Joey's score + score; if total > 9, make no decision; now Joey is inactive; say "Joey glares angrily at the stuck ball." Every turn when the ball is receding and Joey is active: let total be Joey's score + score; if total > 9, make no decision; if the ball is unreachable, make no decision; now Joey is inactive; if a random chance of 1 in 2 succeeds: if a random chance of 1 in 2 succeeds, now the ball is still; otherwise now the ball is approaching; say "Joey connects with your shot. Now the ball is [small white ball condition]!"; otherwise: now the ball is still; say "Joey tries to block, but misses! Back it goes in the center, where it is [small white ball condition]."; increment the score. Every turn when the ball is still and Joey is active: let total be Joey's score + score; if total > 9, make no decision; if the ball is unreachable, make no decision; now Joey is inactive; if a random chance of 1 in 2 succeeds: now the ball is approaching; say "Joey hits the ball solidly down towards your goal. Now it is [small white ball condition]."; otherwise: say "Joey fails to hit the ball in your direction. It remains [small white ball condition]." Every turn: let total be Joey's score + score; if total > 9: if Joey's score > score, end the story saying "Rats! Joey wins!"; if Joey's score < score, end the story finally saying "Victory is yours!"; if Joey's score is score, end the story saying "A perfect tie." Example 141 (**): IPA Shops which each have opening and closing hours, so that it is impossible to go in at the wrong times, and the player is kicked out if he overstays his welcome. Suppose we wanted a game set in a living town, with locations opening and closing at different times of day, and business carrying on as usual. The point might be to force the player to plan his itinerary carefully to hit the right spots at the right times; or we might be writing a more contemplative piece, where part of the enjoyment came from just watching the characters wander around doing their daily business... "IPA" When play begins: now the right hand status line is "[time of day]". The time of day is 9:50 AM. A shop is a kind of room. A shop has a time called the opening hour. The opening hour of the shop is usually 8 AM. A shop has a time called the closing hour. A shop usually has closing hour 6 PM. Check going to a shop (called the target): if the time of day is before the opening hour of the target, say "[The target] is locked up until [the opening hour of the target]." instead. Check going to a shop (called the target): if the time of day is after the closing hour of the target, say "[The target] has been closed since [the closing hour of the target]." instead. Every turn when the location is a shop: let deadline be the closing hour of the location; if the deadline is before the time of day: let target be a random adjacent room which is not a shop; say "You are gently but firmly ushered out, since [the location] is closing."; move the player to the target. The Strip-mall Parking Lot is a room. "Dead Christmas trees are heaped outside the bagel shop. Strips of dirty ice survive along the curb, and in the shadows of the lamp-posts. A wet, almost illegible sheet of algebra homework is plastered to the asphalt. Pinewood Brewing Supply is at the east end of the lot." Pinewood Brewing Supply is a shop. It is east of Parking Lot. The opening hour of Pinewood Brewing Supply is 10:00 AM. The closing hour of Pinewood Brewing Supply is 3:30 PM. "Shelves and shelves of malt and hops; large glass carboys, and plastic tubing; empty bottles; bottle-caps; bottle-labeling kits; starters for vinegar, sourdough, root beer. A sweet malty smell hangs in the air." Instead of going to Brewing Supply when the time of day is before the opening hour of Brewing Supply for the second time: say "You rattle at the door again. 'Hold your horses, for crying out loud,' yells a voice from within." Noah's Bagels is a shop. It is north of the Parking Lot. The opening hour of Noah's Bagels is 6:00 AM. The closing hour of Noah's Bagels is 11:00 AM. "The selection has been somewhat picked over, leaving you with your choice of Pumpernickel, Asiago, or Everything." Test me with "e / e / n / z / s / e / z / e / z / z / e". Example 142 (*): Situation Room Printing the time of day in 24-hour time, as in military situations. Though Inform normally prints times in AM/PM terms, it stores the hours and minutes as 24-hour time; so, if we like, we can easily extract that information again thus: "Situation Room" The Situation Room is a room. To say (relevant time - a time) as 24h time: let H be the hours part of relevant time; let M be the minutes part of relevant time; say "[H]:[if M is less than 10]0[end if][M]". When play begins: now the time of day is 6:09 PM; now the right hand status line is "[time of day as 24h time]". Test me with "z". Example 143 (*): MRE Hunger that eventually kills the player, and foodstuffs that can delay the inevitable by different amounts of time. Many older interactive fiction games required the player to find food and eat on a regular basis in order to avoid death. This effect was often unrealistic (since most people can survive much longer than a few hours without eating) and is often seen as an annoyance. However, for the sake of argument, suppose that we do want to construct a hunger-and-death system. To make things a little more interesting, we will postulate that different foods are differently filling, so that if the player manages to find something really caloric, he is off the hook on his hunger search for a while. We will also implement the system so that the player gets messages when he is hungry, then dies a short time later. (The times involved are ludicrously short, but this allows us to see the effects within a simple example. In a real game we would want to allow a considerably longer timer for the hunger to play out.) First, a little scene-setting: "MRE" When play begins: now the right hand status line is "[time of day]"; say "The procedure was painless at first: increased strength was the first sign, followed by a sensation of delayed time, as though everyone around you moved more slowly. Your ability to dodge and perform feats of agility doubled, then trebled. You were heralded as a triumph of medicine. They told you there would be no side effects worth speaking of. They were wrong." The Base Camp Larder is a room. "This room has been reinforced after each incident -- and there have been dozens in the last two months -- so that it now rivals Fort Knox. Only your new skill and speed enabled you to dodge the motion sensors, knock out the computerized security system, fool the retinal scanner, and punch a hole in the steel containment grating. But you're inside now." Now we define our food, and add some special instructions for what happens to our hunger counters when the food is eaten: Food is a kind of thing. Food is usually edible. Food has a time called the satisfaction period. The satisfaction period of a food is usually 5 minutes. A person can be hungry or replete. The player is hungry. The Larder contains an apple, a candy bar, and a large plate of pasta. The apple, the candy bar, and the pasta are food. The satisfaction period of the apple is 2 minutes. The satisfaction period of the pasta is 125 minutes. Check eating something: if the noun is not food, say "[The noun] might be edible, but it's not what you'd consider really food." Carry out eating something: now the player is replete; hunger resumes in the satisfaction period of the noun from now. The first of those two phrases, "now the player is replete", causes the player to cease to be hungry; the second one sets up a future event in which the hunger sets in again. The length of time until that event depends on how satisfying the specific food is. Now we define that event: At the time when hunger resumes: starvation occurs in three minutes from now; now the player is hungry. At the time when starvation occurs: if the player is hungry, end the story saying "You have starved". Note "if the player is hungry": it is possible that the starvation event will be set up but the player will eat before it occurs; in that case, we want it not to take effect. And now, since we really ought to give the player some warning of what is happening to him: Every turn when the player is hungry: choose a random row in the Table of Hunger Complaints; say "[hunger entry][paragraph break]". Table of Hunger Complaints hunger "Gosh, you're starving." "It feels as though you haven't eaten in days. Weeks, almost." "The world seems to slow down and everything becomes sharper and brighter. You are a hunter, a hunter of foodstuffs." "You find yourself staring at [the random visible thing that is not the player] and wondering how it would taste." Test me with "eat apple / z / z / z / eat candy bar / z / z / z / z / z / z / z / z / z". Example 144 (**): Totality To schedule an eclipse of the sun, which involves a number of related events. First we define the events, and then we create a phrase to schedule them: "Totality" At the time when the penumbra appears: say "The sunlight dies away to an eerie, brownish penumbra." At the time when the eclipse begins: say "The moon passes across the disc of the sun, plunging the world into darkness."; now the Chamber is dark. At the time when the eclipse ends: say "The moon passes away from the sun, and a gloomy penumbral light returns."; now the Chamber is lighted. At the time when normal sunlight returns: say "The sun shines once more bright in the sky, not to be eclipsed again on this spot for another thirty-seven years." To schedule an eclipse for (totality - a time): the penumbra appears at two minutes before totality; the eclipse begins at totality; the eclipse ends at three minutes after totality; normal sunlight returns at five minutes after totality. Now we make use of the new phrase: When play begins, schedule an eclipse for 3:27 PM. The Chamber is a room. The time of day is 3:25 PM. Test me with "z / z / z / z / z / z / z / z / z". We shall see much more about creating phrases later. Their advantage is that they enable a complicated sequence of operations to be given a meaningful name, and that they can be re-used many times as needed. Example 145 (**): Empire A train which follows a schedule, stopping at a number of different locations. Suppose we want to have a train which, at fixed times, arrives at and leaves stations. It should be possible for the player to get on and off the train when it is stopped, but not while the train is in motion. "Empire" The Empire Builder Train is a room. The Train has a room called the station. The station of the Train is Seattle. The description of the Empire Builder is "One of the (relatively) plush long-distance Amtrak trains. You're in a two-story car with toilets and a cafe at one end, not having sprung for a sleeper. [if the station of the Train is the train]Outside the window there is rapidly-passing countryside.[otherwise]Through the windows you can see the [station of the Train] train station.[end if]" Instead of exiting when the player is in the Train: if the station of the Train is the Train: say "The train is not stopped at a station." instead; otherwise: move the player to the station of the train instead. Before going outside when the player is in the Train: try exiting instead. Before going inside when the player is in the station of the Train: move the player to the Train instead. Seattle, Edmonds, Everett, Wenatchee, and Spokane are rooms. The description of a room is usually "The scenic train station of [the location][if the location is the station of the train]. The pompously-titled Empire Builder train is pulled up here, soon to continue its journey towards Chicago[end if]." And now our schedule for the train -- somewhat truncated, admittedly, since the full three-day journey from Seattle to Chicago is a bit long even for an ambitious example. At 4:45 PM: if the player is in the train or the player is in the station of the train, say "The train pulls out of [the station of the Train]!"; now the station of the Train is the Train. At 5:10 PM: now the station of the Train is Edmonds; if the player is in the train or the player is in the station of the train, say "The train pulls into Edmonds and comes to a stop." At 5:17 PM: if the player is in the train or the player is in the station of the train, say "The train pulls out of [the station of the Train], running north along the shore towards Everett."; now the station of the Train is the Train. At 5:39 PM: now the station of the Train is Everett; if the player is in the train or the player is in the station of the train, say "The train arrives in scenic Everett, WA: the last stop before it turns east and heads over the mountains." At 5:44 PM: if the player is in the train or the player is in the station of the train, say "The train pulls out of [the station of the Train] and turns east."; now the station of the Train is the Train. At 8:39 PM: if the player is in the train or the player is in the station of the train, say "In darkness the train rolls into Wenatchee; which is just fine, considering that there is nothing to see here at all."; now the station of the Train is Wenatchee. At 8:44 PM: if the player is in the train or the player is in the station of the train, say "The train pulls out of [the station of the Train] and continues east through the darkness towards Spokane."; now the station of the Train is the Train. Playing this out would of course require near inhuman patience. Let's set things up so that the player at least doesn't have to wait too long for his first departure: The time of day is 4:43 PM. ...and provide fair warning of how slowly time is elapsing. When play begins: now the right hand status line is "[time of day]". Test me with "out / in / z/ z / z / out / z / z / z / z / z / z / z / z / z / z / z / z / z / z / z / z / z / z / z / z / z / z / z / out / in / out / z / z". Test more with "out / z/ z / z / z / z / z / z / z / z / z / z / z / z / z / z / z / z / z / z / z / z / z / z / z / z / z / z / z". Example 146 (***): Hour of the Wren Allowing the player to make an appointment, which is then kept. Here we allow the player to set the time at which some future event is going to happen, rather than letting the game decide. We'll need to borrow the syntax for defining new actions from a later chapter: "Hour of the Wren" When play begins: say "You more or less stumble across them in Central Park: a disparate group of people, all of different ages, sitting in a circle. They aren't talking to one another -- in fact, they seem to be trying very hard to ignore one another, like people in the waiting room of an especially embarrassing kind of doctor. You are about to go around when a woman in a grey pressed suit comes