When instances are adjectives as well as nouns.

§1. Some constant names can be used adjectivally, but not others. This happens when their kind's name coincides with a name for a property, as might for instance happen with "colour". In other words, because it is reasonable that a ball might have a colour, we can declare that "the ball is green", or speak of "something blue", whereas "number" is not a coinciding property, and we would not ordinarily write "the ball is 4".¹

These instances make "enumerative adjectives" because they arise from enumerations such as:

The ball can be red, green or blue.

• ¹ A quirk in English does allow this, implicitly construing number as an age property, but we don't go there in Inform. ↩

adjective_meaning_family *enumerative_amf = NULL;

void InstanceAdjectives::start?Usage of InstanceAdjectives::start:
Knowledge Module - §3(void) {
    enumerative_amf = AdjectiveMeanings::new_family(2);
    METHOD_ADD(enumerative_amf, ASSERT_ADJM_MTID, InstanceAdjectives::assert);
}

int InstanceAdjectives::is_enumerative(adjective_meaning *am) {
    if ((am) && (am->family == enumerative_amf)) return TRUE;
    return FALSE;
}

§2. Let's reconstruct the chain of events, shall we? It has been found that an instance, though a noun, must be used as an adjective: for example, "red". Inform has run through the permissions for the property ("colour") in question, and found that, say, it's a property of doors, scenes and also a single piece of litmus paper. Each of these three is an inference subject, so InferenceSubjects::make_adj_const_domain was called for each in turn.

By different means, those calls all ended up by passing the buck onto the following function: twice with the domain set being a kind ("door" and then "scene"), once with set being null and singleton an instance ("litmus paper").

So, then, we make the instance I have an adjectival use setting the property P when applied to either set or singleton, whichever is not null.

void InstanceAdjectives::make_adjectival?Usage of InstanceAdjectives::make_adjectival:
Instance Subjects - §1
Kind Subjects - §7(instance *I, property *P,
    kind *set, instance *singleton) {
    kind *D = NULL;
    Find the kind domain within which the adjective applies2.1;
    adjective_meaning *am = NULL;
    Create the adjective meaning for this use of the instance2.2;
    Write I6 schemas for asserting and testing this use of the instance2.3;
}

§2.1. Find the kind domain within which the adjective applies2.1 =

    if (singleton) D = Instances::to_kind(singleton);
    else if (set) D = set;
    if (D == NULL) internal_error("No adjectival constant domain");

• This code is used in §2.

§2.2. Create the adjective meaning for this use of the instance2.2 =

    wording NW = Instances::get_name(I, FALSE);
    adjective *adj = Adjectives::declare(NW, NULL);
    am = AdjectiveMeanings::new(enumerative_amf, STORE_POINTER_instance(I), NW);
    I->as_adjective = AdjectiveAmbiguity::add_meaning_to_adjective(am, adj);
    if (singleton) AdjectiveMeaningDomains::set_from_instance(am, singleton);
    else if (set) AdjectiveMeaningDomains::set_from_kind(am, set);

• This code is used in §2.

§2.3. Write I6 schemas for asserting and testing this use of the instance2.3 =

    i6_schema *sch = AdjectiveMeanings::make_schema(am, TEST_ATOM_TASK);
    Calculus::Schemas::modify(sch,
        "%k >> *1 . %n == %d",
            D, RTProperties::iname(P), I->enumeration_index);
    sch = AdjectiveMeanings::make_schema(am, NOW_ATOM_TRUE_TASK);
    Calculus::Schemas::modify(sch,
        "WriteGProperty(%k, *1, %n, %d)",
            D, RTProperties::iname(P), I->enumeration_index);

• This code is used in §2.

§3. Asserting such an adjective simply asserts that the property has this value: for example, asserting "green" on X is saying that the value of the "colour" property of X is "green".

We refuse to assert the falseness of such an adjective since it's unclear what to infer from, e.g., "the ball is not green": is it red, or blue?

int InstanceAdjectives::assert?Usage of InstanceAdjectives::assert:
§1(adjective_meaning_family *f, adjective_meaning *am,
    inference_subject *infs_to_assert_on, int parity) {
    if (parity == FALSE) return FALSE;
    instance *I = RETRIEVE_POINTER_instance(am->family_specific_data);
    property *P = Properties::property_with_same_name_as(Instances::to_kind(I));
    if (P == NULL) internal_error("enumerative adjective on non-property");
    PropertyInferences::draw(infs_to_assert_on, P, Rvalues::from_instance(I));
    return TRUE;
}