To recognise certain kind names as familiar built-in ones.

• §11. Kind names in Inter code
• §12. Kind names in source text

§1. In the Inform source code, we're clearly going to need to refer to some kinds explicitly, and we need a way to do that. We adopt two naming conventions:

• (i) Kinds are written as K_source_text_name, that is, K_ followed by the name of the kind in I7 source text, with spaces made into underscores. For instance, K_number. These are all kind * global variables which are initially NULL, but which, once set, are never changed.
• (ii) Constructors are likewise written as CON_source_text_name if they can be created in source text; or by CON_TEMPLATE_NAME, that is, CON_ followed by the constructor's identifier as given in the command which created it (but with the _TY suffix removed) if not. These are all kind_constructor * global variables which are initially NULL, but which, once set, are never changed.

We will now define all of the K_... and CON_... used by the core of Inform. The kinds module does not need all of these to be created: for example, in a Basic Inform compilation, stored action never will be. The variable K_stored_action will then remain NULL, but will also never be used for anything, so no harm is done.

§2. We begin with the protocol-like "kinds of kinds", the superheroes of the kinds world:

kind *K_value = NULL;
kind *K_stored_value = NULL;
kind *K_pointer_value = NULL;
kind *K_sayable_value = NULL;
kind *K_understandable_value = NULL;
kind *K_arithmetic_value = NULL;
kind *K_real_arithmetic_value = NULL;
kind *K_enumerated_value = NULL;

§3. Next, some awkward punctuation-like special base kinds needed in order to construct things. These are used in combination to make tuples, that is, collections \((K_1, K_2, ..., K_n)\) of kinds of value.

kind_constructor *CON_TUPLE_ENTRY = NULL;
kind *K_void = NULL;
kind_constructor *CON_VOID = NULL;

§4. Thus we store \(()\) (the empty tuple) as CON_VOID, we store \((A)\) as:

    CON_TUPLE_ENTRY
        A
        CON_VOID

so that \(A\) and \((A)\) are distinguishable, and continue. For example, \((A, B, C)\) is:

    CON_TUPLE_ENTRY
        A
        CON_TUPLE_ENTRY
            B
            CON_TUPLE_ENTRY
                C
                CON_VOID

This traditional LISP-like device enables us to store tuples of arbitrary size without need for any constructor of arity greater than 2.

§5. K_unknown plays no role in the type system — as noted in What This Module Does, the way to express "unknown kind" is to use the value NULL. The purpose of K_unknown is purely so that run-time code generated by Inform has a way to mark out empty lists as having entries of no known kind.

kind *K_nil = NULL;
kind_constructor *CON_NIL = NULL;
kind *K_unknown = NULL;
kind_constructor *CON_UNKNOWN = NULL;

§6. CON_INTERMEDIATE is used to represent kinds which are brought into being through uncompleted arithmetic operations: see Dimensions for a full discussion.

kind_constructor *CON_INTERMEDIATE = NULL;

§7. CON_KIND_VARIABLE is used to formally represent kind variables, such as the letter K:

kind_constructor *CON_KIND_VARIABLE = NULL;

§8. So much for the exotica: back onto familiar ground for anyone who uses Inform. Some standard kinds follow. Some belong only to features; if the feature in question is inactive, they will remain NULL and do nothing.

kind *K_equation = NULL;
kind *K_grammatical_gender = NULL;
kind *K_natural_language = NULL;
kind *K_number = NULL;
kind *K_object = NULL;
kind *K_real_number = NULL;
kind *K_response = NULL;
kind *K_snippet = NULL;
kind *K_table = NULL;
kind *K_text = NULL;
kind *K_truth_state = NULL;
kind *K_unicode_character = NULL;
kind *K_use_option = NULL;
kind *K_verb = NULL;

§9. And here are two more standard kinds, but which most Inform users don't realise are there, because they are omitted from the Kinds index:

• (a) K_rulebook_outcome. Rulebooks end in success, failure, no outcome, or possibly one of a range of named alternative outcomes. These all share a single namespace, and the names in question share a single kind of value. It's not a very elegant system, and we really don't want people storing these in variables; we want them to be used only as part of the process of receiving the outcome back. So although there's no technical reason why this kind shouldn't be used for storage, it's hidden from the user.
• (b) K_understanding is used to hold the result of a grammar token. An actual constant value specification of this kind stores a command_grammar * pointer.

kind *K_rulebook_outcome = NULL;
kind *K_understanding = NULL;

§10. Finally, the standard set of constructors:

kind_constructor *CON_list_of = NULL;
kind_constructor *CON_description = NULL;
kind_constructor *CON_relation = NULL;
kind_constructor *CON_rule = NULL;
kind_constructor *CON_rulebook = NULL;
kind_constructor *CON_activity = NULL;
kind_constructor *CON_phrase = NULL;
kind_constructor *CON_property = NULL;
kind_constructor *CON_table_column = NULL;
kind_constructor *CON_combination = NULL;
kind_constructor *CON_variable = NULL;

§11. Kind names in Inter code. We defined some "constant" kinds and constructors above, to provide values like K_number for use in this C source code. We will also want to refer to these kinds in the Inter code generated by Inform, where they will have identifiers such as NUMBER_TY.

So we need a way of pairing up names in these two source codes, and here it is. There is no need for speed here.

define IDENTIFIERS_CORRESPOND(text_of_I6_name, what_have_you)
    if ((sn) && (Str::eq_narrow_string(sn, text_of_I6_name))) return what_have_you;

kind_constructor **FamiliarKinds::known_con?Usage of FamiliarKinds::known_con:
Kind Constructors - §10(text_stream *sn) {
    IDENTIFIERS_CORRESPOND("ACTIVITY_TY", &CON_activity);
    IDENTIFIERS_CORRESPOND("COMBINATION_TY", &CON_combination);
    IDENTIFIERS_CORRESPOND("DESCRIPTION_OF_TY", &CON_description);
    IDENTIFIERS_CORRESPOND("INTERMEDIATE_TY", &CON_INTERMEDIATE);
    IDENTIFIERS_CORRESPOND("KIND_VARIABLE_TY", &CON_KIND_VARIABLE);
    IDENTIFIERS_CORRESPOND("LIST_OF_TY", &CON_list_of);
    IDENTIFIERS_CORRESPOND("PHRASE_TY", &CON_phrase);
    IDENTIFIERS_CORRESPOND("NIL_TY", &CON_NIL);
    IDENTIFIERS_CORRESPOND("VOID_TY", &CON_VOID);
    IDENTIFIERS_CORRESPOND("PROPERTY_TY", &CON_property);
    IDENTIFIERS_CORRESPOND("RELATION_TY", &CON_relation);
    IDENTIFIERS_CORRESPOND("RULE_TY", &CON_rule);
    IDENTIFIERS_CORRESPOND("RULEBOOK_TY", &CON_rulebook);
    IDENTIFIERS_CORRESPOND("TABLE_COLUMN_TY", &CON_table_column);
    IDENTIFIERS_CORRESPOND("TUPLE_ENTRY_TY", &CON_TUPLE_ENTRY);
    IDENTIFIERS_CORRESPOND("UNKNOWN_TY", &CON_UNKNOWN);
    IDENTIFIERS_CORRESPOND("VARIABLE_TY", &CON_variable);
    return NULL;
}

kind **FamiliarKinds::known_kind?Usage of FamiliarKinds::known_kind:
Kind Constructors - §10(text_stream *sn) {
    IDENTIFIERS_CORRESPOND("ARITHMETIC_VALUE_TY", &K_arithmetic_value);
    IDENTIFIERS_CORRESPOND("ENUMERATED_VALUE_TY", &K_enumerated_value);
    IDENTIFIERS_CORRESPOND("EQUATION_TY", &K_equation);
    IDENTIFIERS_CORRESPOND("TEXT_TY", &K_text);
    IDENTIFIERS_CORRESPOND("NUMBER_TY", &K_number);
    IDENTIFIERS_CORRESPOND("OBJECT_TY", &K_object);
    IDENTIFIERS_CORRESPOND("POINTER_VALUE_TY", &K_pointer_value);
    IDENTIFIERS_CORRESPOND("STORED_VALUE_TY", &K_stored_value);
    IDENTIFIERS_CORRESPOND("REAL_ARITHMETIC_VALUE_TY", &K_real_arithmetic_value);
    IDENTIFIERS_CORRESPOND("REAL_NUMBER_TY", &K_real_number);
    IDENTIFIERS_CORRESPOND("RESPONSE_TY", &K_response);
    IDENTIFIERS_CORRESPOND("RULEBOOK_OUTCOME_TY", &K_rulebook_outcome);
    IDENTIFIERS_CORRESPOND("SAYABLE_VALUE_TY", &K_sayable_value);
    IDENTIFIERS_CORRESPOND("UNDERSTANDABLE_VALUE_TY", &K_understandable_value);
    IDENTIFIERS_CORRESPOND("SNIPPET_TY", &K_snippet);
    IDENTIFIERS_CORRESPOND("TABLE_TY", &K_table);
    IDENTIFIERS_CORRESPOND("TRUTH_STATE_TY", &K_truth_state);
    IDENTIFIERS_CORRESPOND("UNDERSTANDING_TY", &K_understanding);
    IDENTIFIERS_CORRESPOND("UNKNOWN_TY", &K_unknown);
    IDENTIFIERS_CORRESPOND("UNICODE_CHARACTER_TY", &K_unicode_character);
    IDENTIFIERS_CORRESPOND("USE_OPTION_TY", &K_use_option);
    IDENTIFIERS_CORRESPOND("VALUE_TY", &K_value);
    IDENTIFIERS_CORRESPOND("VERB_TY", &K_verb);
    IDENTIFIERS_CORRESPOND("NIL_TY", &K_nil);
    IDENTIFIERS_CORRESPOND("VOID_TY", &K_void);
    return NULL;
}

int FamiliarKinds::is_known?Usage of FamiliarKinds::is_known:
Neptune Syntax - §5.2(text_stream *sn) {
    if (FamiliarKinds::known_con(sn)) return TRUE;
    if (FamiliarKinds::known_kind(sn)) return TRUE;
    return FALSE;
}

§12. Kind names in source text. Inform creates the "natural language" kind in source text, not by loading it from a file, but we still need to refer to it in the compiler. Similarly for "grammatical gender". The others here are not referred to in the compiler, but are indexed together.

<notable-linguistic-kinds> ::=
    natural language |
    grammatical gender |
    grammatical tense |
    narrative viewpoint |
    grammatical case

• This is Preform grammar, not regular C code.

§13.

void FamiliarKinds::notice_new_kind?Usage of FamiliarKinds::notice_new_kind:
Kinds - §20(kind *K, wording W) {
    if (<notable-linguistic-kinds>(W)) {
        KindConstructors::mark_as_linguistic(K->construct);
        switch (<<r>>) {
            case 0: K_natural_language = K;
                #ifdef NOTIFY_NATURAL_LANGUAGE_KINDS_CALLBACK
                NOTIFY_NATURAL_LANGUAGE_KINDS_CALLBACK(K);
                #endif
                break;
            case 1: K_grammatical_gender = K; break;
        }
    }
}