§15.14. 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.

In notations like this, only the first-appearing number part is allowed to be negative, and then only when declared with a minus sign:

A secret sign is a kind of value. -2x17 specifies a secret sign with parts mystery and enigma.

Here, the mystery can be negative, but not the enigma.

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.


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