14. Adaptive Text and Responses

A conspicuous difference between interactive fiction and a traditional novel is the point of view from which it's told. Inform usually produces text like:

where a novel would usually write:

Standard interactive fiction (IF) is second person singular, and present tense; most novels are told in the third person singular, and past tense.

But these are just conventions - a few novels, for example, use the so-called present historic ("Napoleon looks up at the sky and sighs. Must Ney always be so doubting?"), and plenty are told in the first person singular ("I always get the shakes before a drop."). Inform allows some of this flexibility, too. The two values:

control the style of the text produced. The story viewpoint has to be one of the values:

(which are actually the six possible values of a kind called "narrative viewpoint"), while the story tense must be one of:

(from a kind called "grammatical tense"). Combining these gives 30 possibilities in all, though only a few are at all commonly used.

It's important to make a very large caveat here: Inform uses these settings in producing the replies ("responses") by the built-in actions, but the only way for all of our own text to have a particular tense or narrative viewpoint is to write it that way. If we write:

then we're likely to see the following peculiar transcript:

That's because the response ("We couldn't go that way") was constructed to follow the settings for viewpoint and tense, but the fixed text of the room description wasn't. In fact there are ways to write the room description so that it would adapt itself automatically, as we'll see, but it takes a fair amount of work. More simply:

In short, tense and viewpoint switching is neat, but it isn't magic.

If we want to write text which will work in whatever the current tense is, the following turn out to be useful little conveniences:

Paying attention to the tense and viewpoint is one reason why text might need to adapt. Another is that it might need to adapt according to whether nouns are singular or plural, or whether it talks about the player or some third party. For example, the following rule isn't ideal:

Most of the time it's fine ("The V-ray is pinned down by Dr Zarkov's force field"), but then:

Which is a little unfortunate. But the correction is very easy:

The result is much better: "The V-ray is pinned down…"; "You are…"; "The condensers are…". In fact, it's also convenient because it adapts to the story viewpoint and story tense: "The condensers will be pinned down…"; "He was pinned down…".

How does Inform do this? The answer is not that "[are]" is a specially-written text substitution. In fact Inform can do this with any verb that it has a definition of. For example,

would also adapt itself - "The V-ray carries too much static charge", and so on. There aren't many verbs built in to Inform, but "[have]" and "[carry]" and "[wear]" and "[can]" may be useful, and "[can see]" and "[can touch]". Negative forms like "[are not]" are also available:

might produce "The V-ray will not be able to touch the ionizer terminal.", for example.

As these examples hint, the verb adapts itself to the most recently printed object name. All of this only works if the previous object's name is printed from a substitution. So:

will work -- correctly forming "The condensers are working.", "The condensers will be working." or "The condensers were working.", according to the story tense -- but

probably won't work. Inform doesn't have any way to understand the raw text outside of the text substitution marks "[" and "]", and it doesn't recognise "The condensers" as being something's name.

Something else to be careful with is the use of lists. If we write this:

then Inform is likely to print:

because it looks at the most recently named object - the V-ray, singular - to decide whether to use "is" or "are". On the other hand, Inform gets this right:

Because Inform constructs the list itself, it's able to appreciate that the things listed are jointly the subject of the verb, and it uses that information to decide on "is" or "are". So:

If we need an adaptive message with a verb which doesn't belong to Inform's built-in set, all we need do is define it. In the previous chapter we defined verbs by giving them meanings, but in fact that's optional. For example:

defines a verb without telling Inform what it means. Inform will throw a Problem message if we try to write text like:

because, after all, it doesn't know what "retrofit" means. But it does still know how to print it, so this works:

which might come out as "Dale retrofits the Mecha-Mole", or "Barin's archers retrofitted the Mecha-Mole", and so on.

This is especially neat for writing a single response to an action which works regardless of who the actor was. For example, the Standard Rules include:

And this can make either:

In second-person-singular IF, the player is always "you". Many messages look like so:

where the subject, or the object, of the sentence is "you". But what if we want to have this text adapt itself to different narrative viewpoints?

The solution is to use the following:

The capitalised and uncapitalised versions are identical except, of course, that the initial letter of the resulting text is upper case in one but not the other. As examples of these:

Notice that all five of these forms are differently worded, in English. That's the reason why we use the plural to write them - the traditional second person plural forms would be "you", "you", "your", "yours" and "yourself", so we wouldn't know if "[you]" was supposed to be the subject or the object of the verb. So the convention with all of these adaptive forms is that we use "we" and its variations. (That's also why the verbs are written in the plural - "[carry]", not "[carries]".)

The family in the previous section - "[we]", "[us]", "[our]", "[ours]", "[ourselves]" - always referred to the player. But we also sometimes want to refer to other things without naming them. For example, how should we adapt this?

We can easily make the verb adapt - change the "has" to "[have]" - but the trick here is to make the "It" adapt to cases where what's examined is plural, or animate. What we want is:

For example, this produces:

Note that we have to say "[regarding the noun]", not just start in with "[They]", because nothing has been named so far in the sentence - so Inform doesn't know what object it refers to. "[regarding the noun]" prints nothing, and simply tells the printing part of Inform that the subject has changed.

This isn't always needed:

works fine, because printing "[the noun]" changes the subject to that, and then "[they]" agrees with it automatically. The text might come out, for example, as:

We have a family of five text substitutions here, matching those in the previous section:

There's also the peculiar impersonal non-object for English sentences like "It is raining" or "There are books":

These look pointless - but consider the two texts

The first one risks printing "We took the scissors. It rain harder.", because it makes "[rain]" agree with "scissors", which are plural. But the second text makes "[rain]" agree with "[it]". And, as a convenience:

do the obvious thing using the current story tense.

Finally, we occasionally want to agree with a number:

Consider the following message: how might we make this adaptive?

The verbal part is easy enough, but "that" needs a new feature.

This could then adapt to, say,

Notice that it's "[regarding the noun][those]", not just "[those]". If we wrote "[those]", Inform would make it agree with the player, who was printed earlier in the sentence by the "[We]".

Lastly, how about:

This time we want:

which might adapt to, say,

Actually, "[regarding …]" can be used for a description of possibly many items, too. For example:

Every turn when the player carries something:

So if the player carries just a single coin, say, this automatically becomes:

but if the player carries a pair of scissors (a single plural-named item) or a coin and an iPhone, it becomes:

Once again these text substitutions are available in capitalised and uncapitalised forms:

In fact "[Those]" and "[those]" do subtly different things, besides the capital letter, because "[Those]" expects to be the subject of the sentence and "[those]" the object, and this makes a difference if the noun in question is a person. If the noun is an odious person called Tilly then

would come out as "She is unacceptable" - so "[Those]" becomes "She" - but "You've never liked her" - so "[those]" becomes "her". If we need these in different cases, we can explicitly ask for that:

English uses so-called "modal verbs" to change a sentence so that it talks about something only possibly happening. For example, the sentence "Fred goes to school" can be modified to "Fred must go to school", "Fred should go to school" or even "Fred might go to school".

Inform supports the use of modal verbs in text substitutions. For example,

would in the present tense come out as "Fred might go to school.", but could alternatively be "Fred might have gone to school." As this example shows, all that's needed is to take a verb we'll call V - this case, "go" - and we can write any of these:

That helps us to handle informal usages like this one:

To make this message adaptive, we write:

which can adapt in surprising ways -- "They won't be able to go that way.", for example.

Note that the verb V has to be one that Inform knows. But that's easy:

and then

could produce "Fred might not have discombobulated so easily", for example.

Contractions usually take the form of part of a word being missed out and replaced by an apostrophe. We've already seen "[can't]", "[couldn't]", "[mayn't]", "[mightn't]", "[mustn't]", "[shouldn't]" and "[wouldn't]", for example. But Inform supports other contractions, too, as follows.

The English verbs "to be" and "to have" are unique in having contracted forms, which we can write "['re]" and "['ve]", like this:

which might produce, say, "I've got rhythm. I'm cool.", or "He'll have rhythm. He'll be cool.", or "You had got rhythm. You were cool." (The contractions don't appear in the past tense; but the spacing fixes itself automatically.)

The Standard Rules often use a special text substitution for responses like this one:

This is exactly like "[Those]['re] hardly portable" except that if the plural is needed, Inform prints "They're hardly portable" rather than the correct, but not quite idiomatic, "Those're hardly portable". (If we wrote "[They]['re] …", that would get the plural form right, but then the singular would be "It's hardly portable" not "That's hardly portable".)

Only a few English verbs have contracted negative forms, beyond those already mentioned. Inform knows these informal forms:

For example,

can produce variations like these:

Each verb known to Inform is actually a value of the kind "verb". To refer to a verb as a value, we have to put the word "verb" in front, as in these examples:

all of which appear in the Standard Rules.

Two adjectives are provided for use with verbs: "modal" (or "non-modal") to pick out verbs like might, could, should, and so on; and "meaningful" (or "meaningless") to pick out verbs which have a defined meaning as an Inform relation. For example, in the Standard Rules, the verb contain is meaningful, the verb might is modal, and the verb provoke is meaningless.

If V has a meaning as a relation of objects, then "meaning of V" produces that relation. For example,

produces:

As this demonstrates, if a verb has no meaning, or its meaning doesn't relate to objects, we get just the equality relation.

In fact, Inform even defines a verb "to mean": it's meaningful, and its meaning is the meaning relation. Thus:

is true. More usefully, we can search our vocabulary like this:

which, unless any non-Standard Rules definitions have been added, produces:

Note that the meaning relation can't be changed at run-time: it is not clear what it would even mean to do something like -

with the story already started, so this will produce a problem message.

Note that the verb doesn't have to be named explicitly for use by the adapt or negate phrases, so for example:

produces:

Lastly, we can get at three other useful parts of a verb, too. These aren't adaptive, of course: a verb only has one infinitive form.

Most of the text which the player sees is drawn from the source, but mixed in with this are messages apparently added by Inform itself - usually in the form of short sentences saying that something has been done, or that something can't be done. Such pieces of text are called "responses", because they are almost always replies to commands. For example:

Responses like this, which don't appear anywhere in the source text, come from one of the extensions being used; most often from the Standard Rules, the "extension" which is automatically included in every project. The SR contain many small rules, and almost all of these are capable of producing one or two standard responses. These are labelled with the rule's name and then a bracketed letter - (A), (B), (C), … as needed so that every response has its own unique name. There's nothing very mysterious about how this is done. For example, here is a rule with one response:

which makes the familiar text "You are carrying nothing." a response named:

These names are actually values, belonging to the kind "response". Because of that, if we try this:

Inform will produce

since we gave Inform a value to print, and that's just what it then did. As an alternative:

Thus,

produces

These responses are named so that they can be changed. Most IF authors dislike one or two of the existing responses, and some would like to change almost all of them to give the text a different style; and extensions for IF in languages other than English change literally every response, of course.

It's very easy to change responses:

and we can even do this dynamically during play:

just as if we were setting a variable.

In practice we can't change these responses unless we know what they're called. One way to find out is just to read through the extensions we're using, but that's a laborious process. A more practical answer is to type:

which replies by listing the sets of responses currently available; for example, it says that RESPONSES 1 is the set of responses for the Standard Rules. We can then type exactly that:

and so on. This lists all of the responses, rule by rule, along with their current texts.