16.11. Understanding values

| Chapter 16: Understanding |

| 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?).

297
| Example 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"). |
RB

298
| Example Baritone, Bass Letting the player pick a gender (or perhaps other characteristics) before starting play. |
RB

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