Writing in Inform

WI §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:

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 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:

We have already seen that we can list the items fitting a given description:

It's also sometimes convenient to count them up:

It is because descriptions are so widely useful that they deserve a chapter of their own, and this is it.

WI §6.2. Adjectives and nouns

Descriptions can contain a noun, but need not, and can contain any number of adjectives:

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:

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.)

WI §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

...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.

WI §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:

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 talk about rooms being occupied. We could give a second definition thus:

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:

The "rather than..." part of the definition is optional, but it saves having to write a boringly similar definition of "unoccupied" out in longhand. (Note that Inform does not guess the meaning of "unoccupied" unless it has been explicitly told it. Such guesses are too risky, when so many "un-" words fail to conform to this pattern: "unified", "uncle", "ungulate" and so on.)

Newly defined adjectives cannot be used when creating things, because they are not explicit enough. Inform could not satisfy:

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:

which is a good deal easier to read than

WI §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:

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:

Similarly, two useful adjectives are built in to talk about text:

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:

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,

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:

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.

WI §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:

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:

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:

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:

Inform then judges whether someone is or is not "tall" using different standards for men and for women, and

creates a man 72 inches tall and a woman 68 inches tall.

WI §6.7. Comparatives

The special definitions in the previous section have a further effect. When we define:

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,

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:

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:

WI §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

then we can talk about things like this:

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).

WI §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,

are all valid descriptions. These are really abbreviations, having missed out the words "which is" or "who is", as appropriate:

and indeed those are also valid descriptions. The other sentence verbs can all be used here, too. So for instance:

And sometimes we should spell out "who is" regardless:

Since these clauses can be attached to the end of any valid description, descriptions can grow longer still:

Pedants who flinch when "which" is used to introduce a restrictive clause are welcome to use "that" instead.

WI §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:

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:

Another reason might be that we want to create something but not put it anywhere. If Inform reads the sentence:

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:

Or even:

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:

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:

or, of course, we needn't use "there is" at all:

And we can also test non-existence:

WI §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:

or if we ask a question like:

This kind of "in" talks only about direct containment. If we ask

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

...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

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:

is meaning 2, because "Garden Area" is the name of a region. That seems fair enough, but values are indeed 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

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:

because "regionally in" is always meaning 2 of "in".

WI §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:

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) 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,

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.

WI §6.13. To be able to see and touch

Two of the adjectives built into Inform are:

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:

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:

are synonymous. Similarly for touch; and we can write such conditions as

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:

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.

WI §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:

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:

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:

Alternatively, and particularly if the direction is not a constant,

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.

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:

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.)

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:

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.

WI §6.15. All, each and every

When testing conditions, we normally talk only about specific things, or else ask if a particular circumstance happens:

But we can also use "all", "each" or "every" to check the whole range:

Inform allows other English "determiners" (as they are sometimes called), as well:

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:

though it may be clearer style to find a positive way of putting things:

All, each and every can be applied to values, too - but only in some cases. For example, suppose we write:

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:

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:

(even supposing the adjective "palindromic" has been defined) - there are practically infinitely many possible numbers and texts, so the search cannot sensibly be done.

WI §6.16. Counting while comparing

Lastly we can also ask for a more specific number of possibilities, like so:

Likewise for "less than", "at least", "all except". Something to watch out for is that

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

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:

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.)