Documentation

• Section: Grouping Some Relations Together
• Section: The Printing a Relation Activity
• Section: Reference
• Section: Esoterica

Section: Grouping Some Relations Together

We can already pass "abstract-relations" to phrases. This is typically used for pathfinding.
    let footprints be the number of steps via the acts-with relation from Jodie Foster to Kevin Bacon;

This extension provides us a "holds between" phrase that decides whether or not the abstract-relation is true for the two objects given it. A variant, "holds between X and Y or vice-versa", will try X~Y and Y~X and return true if at least one of those was true.

The intended usage is to group and iterate through object-to-object relations involving feelings and knowledge. The built-in physical object relations of Inform are also supported. Relations to numbers and kinds of value are not supported.

We accomplish our primary tasks like so:
    To decide whether (sponsor - a person) has a reason to help (supplicant - a person):
        let many reasons be { the love relation, the marriage relation, alliance relation, the owed-favor relation };
        repeat with a relationship running through many reasons begin;
            if a relationship holds between the sponsor and the supplicant, decide yes;
        end repeat;
        decide no.
    
    To decide what indexed text is reason for (sponsor - a person) to help (supplicant - a person):
        let many reasons be { the love relation, the marriage relation, alliance relation, the owed-favor relation };
        repeat with relationship running through many reasons begin;
            if the relationship holds between the sponsor and the supplicant, decide on the name of the relation relationship;
        end repeat;
        decide on "".
    
    To decide whether (R - an abstract-relation) is a favorite:
        let L be { the love relation, the friendship relation, alliance relation, marriage relation };
        decide on whether or not R is listed in L.


A phrase cannot decide on a relation, so we decide on the text of its name instead. We also cannot put relations directly into tables:
    Table of Emotional Relationships

	relationship
	an abstract-relation
	the love relation
	the alliance relation

But curiously, we can put them into lists, and then put the lists into tables:
    A relation group is a kind of value. Some relation groups are defined by the table of relationships.
    
    Table of Relationships

	mood [a relation group]	articulate [a list of abstract-relations]
	puzzly	{ the incorporation relation, the containment relation }
	mushy	{ love relation, marriage relation }

    
    After looking:
        let vagueness be a random relation group;
        say "'I'm kinda in a [vagueness] mood.'";
        choose row with a mood of vagueness from the table of relationships;
        repeat with relationship running through the articulate entry begin;
            say "Are you in the mood for some [relationship]?";
        end repeat.


Another thing we cannot do is directly create a variable to hold a relation:
    let configurations be { the containment relation, friendship relation };
    let config be entry 2 of configurations;

We have to reference the relation indirectly, every time:
    let configurations be { the containment relation, friendship relation };
    if entry 2 of configurations holds between....

Our only way of putting a relation into a variable (other than converting it to a number with "as a number") is to pass it to a To phrase, or put a list of them in a repeat loop.