To declare I6 constants and arrays.

• §2. Constant values
• §3. Arrays
• §5. Actions
• §6. Literals

§1.

void I6TargetConstants::create_generator?Usage of I6TargetConstants::create_generator:
Generating Inform 6 - §1(code_generator *gtr) {
    METHOD_ADD(gtr, DECLARE_CONSTANT_MTID, I6TargetConstants::declare_constant);
    METHOD_ADD(gtr, BEGIN_ARRAY_MTID, I6TargetConstants::begin_array);
    METHOD_ADD(gtr, ARRAY_ENTRY_MTID, I6TargetConstants::array_entry);
    METHOD_ADD(gtr, END_ARRAY_MTID, I6TargetConstants::end_array);
    METHOD_ADD(gtr, NEW_ACTION_MTID, I6TargetConstants::new_action);
    METHOD_ADD(gtr, COMPILE_DICTIONARY_WORD_MTID, I6TargetConstants::compile_dictionary_word);
    METHOD_ADD(gtr, COMPILE_LITERAL_NUMBER_MTID, I6TargetConstants::compile_literal_number);
    METHOD_ADD(gtr, COMPILE_LITERAL_REAL_MTID, I6TargetConstants::compile_literal_real);
    METHOD_ADD(gtr, COMPILE_LITERAL_TEXT_MTID, I6TargetConstants::compile_literal_text);
    METHOD_ADD(gtr, COMPILE_LITERAL_SYMBOL_MTID, I6TargetConstants::compile_literal_symbol);
}

§2. Constant values. Constants are layered by depth, so that if the initial value for X depends on that for Y then the declaration for Y will always be placed earlier in the code than that for X. See Code Generation for how this is done.

void I6TargetConstants::declare_constant?Usage of I6TargetConstants::declare_constant:
§1(code_generator *gtr, code_generation *gen,
    inter_symbol *const_s, int form, text_stream *val) {
    text_stream *const_name = InterSymbol::trans(const_s);
    Leave undeclared any array used as a value of a property2.1;
    Leave undeclared any constant auto-declared by the I6 compiler2.2;

    int depth = 1;
    if (const_s) depth = ConstantInstruction::constant_depth(const_s);
    segmentation_pos saved = CodeGen::select_layered(gen, constants_I7CGS, depth);
    text_stream *OUT = CodeGen::current(gen);

    if (Str::eq(const_name, I"Release")) Declare the Release constant with a directive2.4;
    if (Str::eq(const_name, I"Serial")) Declare the Serial constant with a directive2.5;

    int ifndef_me = FALSE;
    Certain constants should be declared only if I6 has not already declared them2.3;
    if (ifndef_me) WRITE("#ifndef %S;\n", const_name);
        WRITE("Constant %S = ", const_name);
        VanillaConstants::definition_value(gen, form, const_s, val);
        WRITE(";\n");
    if (ifndef_me) WRITE("#endif;\n");
    CodeGen::deselect(gen, saved);
}

§2.1. A curious feature of Inform, going back to the original 1970s design of the Z-machine VM, is that properties of objects can be small arrays rather than single values. These are, for some reason, called "inline arrays". The I6 generator is going to take advantage of this feature: if it sees that a property is actually an address of a small array, it will compile that array directly into the body of the relevant object or class declaration. It therefore does not need to declare the name of this small array, and so —

Leave undeclared any array used as a value of a property2.1 =

    if (ConstantInstruction::is_inline(const_s))
        return;

• This code is used in §2.

§2.2. We cannot declare these constants because they exist automatically, and declaring them will therefore throw an error message calling them duplicates. (The initial values these have in the Inter tree are perfectly correct, and on other targets they will be compiled normally.)

The FLOAT_* constants are defined only when I6 compiles to the Glulx VM, but then, they are only present in the Inter tree when we are headed that way anyway.

Leave undeclared any constant auto-declared by the I6 compiler2.2 =

    if ((Str::eq(const_name, I"FLOAT_INFINITY")) ||
        (Str::eq(const_name, I"FLOAT_NINFINITY")) ||
        (Str::eq(const_name, I"FLOAT_NAN")) ||
        (Str::eq(const_name, I"nothing")) ||
        (Str::eq(const_name, I"#dict_par1")) ||
        (Str::eq(const_name, I"#dict_par2")))
        return;

• This code is used in §2.

§2.3. In addition to those are constants which are only sometimes auto-declared, depending on, for example, the choice of virtual machine I6 is compiling to. Some of this goes back to the fact that support for the Glulx VM was a retrofit to the I6 compiler some years after its original design: there was no need for a TARGET_ZCODE constant back when Z-code was the only code it could make, for example.

Certain constants should be declared only if I6 has not already declared them2.3 =

    if ((Str::eq(const_name, I"WORDSIZE")) ||
        (Str::eq(const_name, I"TARGET_ZCODE")) ||
        (Str::eq(const_name, I"TARGET_GLULX")) ||
        (Str::eq(const_name, I"DICT_WORD_SIZE")) ||
        (Str::eq(const_name, I"DICT_ENTRY_BYTES")) ||
        (Str::eq(const_name, I"DEBUG")) ||
        (Str::eq(const_name, I"cap_short_name"))) {
        ifndef_me = TRUE;
    }

• This code is used in §2.

§2.4. The release number is just another constant integer, but in I6 it has to be declared with the Release directive, so:

Declare the Release constant with a directive2.4 =

    WRITE("Release ");
    VanillaConstants::definition_value(gen, form, const_s, val);
    WRITE(";\n");
    return;

• This code is used in §2.

§2.5. Likewise the Serial code (e.g., "211010"), which must be a double-quoted literal:

Declare the Serial constant with a directive2.5 =

    WRITE("Serial ");
    VanillaConstants::definition_value(gen, form, const_s, val);
    WRITE(";\n");
    return;

• This code is used in §2.

§3. Arrays. Now for arrays, which we turn into Verb or Array directives in I6. We will return FALSE in the Verb case to tell Vanilla that the entire array has now been declared, so it need do nothing further; TRUE in the more typical Array case, whereupon Vanilla will lead us through the rest of the declaration.

int I6TargetConstants::begin_array?Usage of I6TargetConstants::begin_array:
§1(code_generator *gtr, code_generation *gen,
    text_stream *array_name, inter_symbol *array_s, inter_tree_node *P, int format,
    int zero_count, segmentation_pos *saved) {
    if (ConstantInstruction::list_format(P) == CONST_LIST_FORMAT_GRAMMAR) {
        Write a complete I6 Verb directive3.1;
        return FALSE;
    } else {
        Begin an I6 Array directive3.2;
        return TRUE;
    }
}

§3.1. Here we hijack a command-verb grammar array entirely. Verb directives in I6 have a fruity sort of syntax, using reserved words not found elsewhere, and punctuation markers like * and ->, and constructs like scope=F for functions F, and so on; so it's not really practical to create such directives as if they were any other arrays. Here goes:

Write a complete I6 Verb directive3.1 =

    if (saved) *saved = CodeGen::select(gen, command_grammar_I7CGS);
    text_stream *OUT = CodeGen::current(gen);
    WRITE("Verb");
    int marker = NOT_APPLICABLE;
    for (int i=0; i<ConstantInstruction::list_len(P); i++) {
        WRITE(" ");
        inter_pair val = ConstantInstruction::list_entry(P, i);
        if (InterValuePairs::is_symbolic(val)) {
            inter_symbol *A = InterValuePairs::to_symbol_at(val, P);
            if (A == NULL) internal_error("bad aliased symbol");
            text_stream *S = InterSymbol::trans(A);
                 if (A == RunningPipelines::get_symbol(gen->from_step, verb_directive_meta_RPSYM))        WRITE("meta");
            else if (A == RunningPipelines::get_symbol(gen->from_step, verb_directive_divider_RPSYM))     WRITE("\n\t*");
            else if (A == RunningPipelines::get_symbol(gen->from_step, verb_directive_reverse_RPSYM))     WRITE("reverse");
            else if (A == RunningPipelines::get_symbol(gen->from_step, verb_directive_slash_RPSYM))       WRITE("/");
            else if (A == RunningPipelines::get_symbol(gen->from_step, verb_directive_result_RPSYM))      WRITE("->");
            else if (A == RunningPipelines::get_symbol(gen->from_step, verb_directive_special_RPSYM))     WRITE("special");
            else if (A == RunningPipelines::get_symbol(gen->from_step, verb_directive_number_RPSYM))      WRITE("number");
            else if (A == RunningPipelines::get_symbol(gen->from_step, verb_directive_noun_RPSYM))        WRITE("noun");
            else if (A == RunningPipelines::get_symbol(gen->from_step, verb_directive_multi_RPSYM))       WRITE("multi");
            else if (A == RunningPipelines::get_symbol(gen->from_step, verb_directive_multiinside_RPSYM)) WRITE("multiinside");
            else if (A == RunningPipelines::get_symbol(gen->from_step, verb_directive_multiheld_RPSYM))   WRITE("multiheld");
            else if (A == RunningPipelines::get_symbol(gen->from_step, verb_directive_held_RPSYM))        WRITE("held");
            else if (A == RunningPipelines::get_symbol(gen->from_step, verb_directive_creature_RPSYM))    WRITE("creature");
            else if (A == RunningPipelines::get_symbol(gen->from_step, verb_directive_topic_RPSYM))       WRITE("topic");
            else if (A == RunningPipelines::get_symbol(gen->from_step, verb_directive_multiexcept_RPSYM)) WRITE("multiexcept");
            else if (A == RunningPipelines::get_symbol(gen->from_step, verb_directive_noun_filter_RPSYM)) marker = TRUE;
            else if (A == RunningPipelines::get_symbol(gen->from_step, verb_directive_scope_filter_RPSYM)) marker = FALSE;
            else if (Str::begins_with_wide_string(S, U"##")) Write without sharps3.1.1
            else {
                if (marker == FALSE) WRITE("scope=");
                if (marker == TRUE)  WRITE("noun=");
                I6TargetConstants::compile_literal_symbol(gtr, gen, A);
                marker = NOT_APPLICABLE;
            }
        } else {
            CodeGen::pair(gen, P, val);
        }
    }
    WRITE(";\n");

• This code is used in §3.

§3.1.1. When an action is named in a Verb directive, it appears without its ## prefix; so the following ensures that we write, say,

    Verb 'help' * -> Help;

rather than

    Verb 'help' * -> ##Help;

which would be a more consistent design, but is a syntax error in I6.

Write without sharps3.1.1 =

    LOOP_THROUGH_TEXT(pos, S)
        if (pos.index >= 2)
            PUT(Str::get(pos));

• This code is used in §3.1.

§3.2. Enough of verbs. A general array is more straightforward, except for a quirk (read: blunder) in I6 syntax. In I6,

    Array X table 10 20 30;

makes a table array with three entries, so that X ends up as a pointer to a block of four words in memory: 3, 10, 20, 30. However,

    Array X table 10;

makes a table with 10 entries, initially zeroes, so that X points to the block 10, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0. We do not want this: there are times when we genuinely need a 1-entry table array. So we use the alternate syntax, provided by Inform 6 since at least 2000 but for some reason not documented in the DM4:

    Array X table [ 10 ];

Begin an I6 Array directive3.2 =

    if (saved) *saved = CodeGen::select(gen, arrays_I7CGS);
    text_stream *OUT = CodeGen::current(gen);
    WRITE("Array %S ", array_name);
    switch (format) {
        case WORD_ARRAY_FORMAT: WRITE("-->"); break;
        case BYTE_ARRAY_FORMAT: WRITE("->"); break;
        case TABLE_ARRAY_FORMAT: WRITE("table"); break;
        case BUFFER_ARRAY_FORMAT: WRITE("buffer"); break;
    }
    if (zero_count >= 0) {
        WRITE(" %d", zero_count);
    } else {
        WRITE(" [");
    }

• This code is used in §3.

§4. A further quirk (again, blunder) is that I6 has no delimiter syntax to mark off one entry from the next — in most languages, such as C, a comma would be used, but I6 uses only white space.

That's fine until entries begin with operators which are ambiguously unary or binary — in other words, with minus signs. In I6, this:

    Array X --> [ 2 4 -5 ];

makes a two-element array, with X pointing to 2, -1, because 4 -5 is read as a binary operation (subtraction), not as 4 followed by a unary operation (negation) applied to 5.

We avoid this by placing semicolons after every entry, just in case:

    Array X --> [ 2; 4; -5; ];

Again, though undocumented in the DM4, this is a long-established syntax in I6.

void I6TargetConstants::array_entry?Usage of I6TargetConstants::array_entry:
§1(code_generator *gtr, code_generation *gen,
    text_stream *entry, int format) {
    text_stream *OUT = CodeGen::current(gen);
    WRITE(" %S;", entry);
}

void I6TargetConstants::end_array?Usage of I6TargetConstants::end_array:
§1(code_generator *gtr, code_generation *gen, int format,
    int zero_count, segmentation_pos *saved) {
    text_stream *OUT = CodeGen::current(gen);
    if (zero_count < 0) WRITE(" ];\n");
    else WRITE("; ! blank with extent %d\n", zero_count);
    if (saved) CodeGen::deselect(gen, *saved);
}

§5. Actions. In I6, actions are implicitly created when they are used in command-grammar syntax (i.e. in Verb directives); so if true_action is set, we do nothing.

Fake actions, where true_action is not set, are those which are valid actions in principle but which never occur in any command grammar. It follows that these must be explicitly declared, which we do with the I6 Fake_Action directive:

void I6TargetConstants::new_action?Usage of I6TargetConstants::new_action:
§1(code_generator *gtr, code_generation *gen,
    text_stream *name, int true_action, int N) {
    if (true_action == FALSE) {
        segmentation_pos saved = CodeGen::select(gen, fake_actions_I7CGS);
        text_stream *OUT = CodeGen::current(gen);
        WRITE("Fake_Action %S;\n", name);
        CodeGen::deselect(gen, saved);
    }
}

§6. Literals. Integer literals are written in the obvious way. In hexadecimal, I6 uses a single $ prefix. Real literals also begin with a $, but then continue with a real-number notation including a decimal point. The same notation is used by Inter, so we need do nothing to modify it here.

void I6TargetConstants::compile_literal_number?Usage of I6TargetConstants::compile_literal_number:
§1(code_generator *gtr,
    code_generation *gen, inter_ti val, int hex_mode) {
    text_stream *OUT = CodeGen::current(gen);
    if (hex_mode) WRITE("$%x", val);
    else WRITE("%d", val);
}

void I6TargetConstants::compile_literal_real?Usage of I6TargetConstants::compile_literal_real:
§1(code_generator *gtr,
    code_generation *gen, text_stream *textual) {
    text_stream *OUT = CodeGen::current(gen);
    if ((Str::get_first_char(textual) != '-') && (Str::get_first_char(textual) != '+'))
        WRITE("$+%S", textual);
    else
        WRITE("$%S", textual);
}

§7. Dictionary words — those used in the command parser grammar — are written in single quotation marks and have their own peculiar syntax: see the Inform Designer's Manual, 4th edition, for more. In particular note that we compile a one-character dword to, say, 'z//' not 'z': the double-slash is meaningless there, but distinguishes this from the character constant 'z', which evaluates to the ZSCII code for lower-case Z.

void I6TargetConstants::compile_dictionary_word?Usage of I6TargetConstants::compile_dictionary_word:
§1(code_generator *gtr, code_generation *gen,
    text_stream *S, int pluralise) {
    text_stream *OUT = CodeGen::current(gen);
    int n = 0;
    WRITE("'");
    LOOP_THROUGH_TEXT(pos, S) {
        inchar32_t c = Str::get(pos);
        if (c >= 0x100) WRITE("@{%04x}", c);
        else {
            switch(c) {
                case '/': if (Str::len(S) == 1) WRITE("@{2F}"); else WRITE("/"); break;
                case '\'': WRITE("^"); break;
                case '^': WRITE("@{5E}"); break;
                case '~': WRITE("@{7E}"); break;
                case '@': WRITE("@{40}"); break;
                default: PUT(c);
            }
        }
        if ((TargetVMs::is_16_bit(gen->for_VM)) && (n++ > 32)) break;
    }
    if (pluralise) WRITE("//p");
    else if (Str::len(S) == 1) WRITE("//");
    WRITE("'");
}

§8. Literal texts, written in double quotation marks, are more of a slog to get right, and have subtly different escape-character syntax: again, see the DM4.

Note that the PRINTING_LTM literal text mode is enabled when the following is used for text appearing in an I6 print statement, rather than as an I6 value.

The BOX_LTM mode is used for quotation text appearing in the I6 box statement.

If you think it surprising that the escape characters would need to use different syntaxes in these three cases, I won't argue.

void I6TargetConstants::compile_literal_text?Usage of I6TargetConstants::compile_literal_text:
§1(code_generator *gtr, code_generation *gen,
    text_stream *S, int escape_mode) {
    text_stream *OUT = CodeGen::current(gen);
    WRITE("\"");
    if (escape_mode == FALSE) {
        WRITE("%S", S);
    } else if (gen->literal_text_mode == BOX_LTM) {
        Compile literal text in box mode8.1;
    } else if (gen->literal_text_mode == PRINTING_LTM) {
        Compile literal text in print-statement mode8.3;
    } else {
        Compile literal text in value mode8.2;
    }
    WRITE("\"");
}

§8.1. Box mode and value mode are the same except for their handling of newlines. Note that the two-digit hex values in braces are the ASCII values of the characters being written.

Compile literal text in box mode8.1 =

    LOOP_THROUGH_TEXT(pos, S) {
        inchar32_t c = Str::get(pos);
        if (c >= 0x100) WRITE("@{%04x}", c);
        else {
            switch(c) {
                case '@': WRITE("@{40}"); break;
                case '"': WRITE("~"); break;
                case '^': WRITE("@{5E}"); break;
                case '~': WRITE("@{7E}"); break;
                case '\\': WRITE("@{5C}"); break;
                case '\t': WRITE(" "); break;
                case '\n': WRITE("\"\n\""); break;
                case NEWLINE_IN_STRING: WRITE("\"\n\""); break;
                default: PUT(c);
            }
        }
    }

• This code is used in §8.

§8.2. Compile literal text in value mode8.2 =

    LOOP_THROUGH_TEXT(pos, S) {
        inchar32_t c = Str::get(pos);
        if (c >= 0x100) WRITE("@{%04x}", c);
        else {
            switch(c) {
                case '@': WRITE("@{40}"); break;
                case '"': WRITE("~"); break;
                case '^': WRITE("@{5E}"); break;
                case '~': WRITE("@{7E}"); break;
                case '\\': WRITE("@{5C}"); break;
                case '\t': WRITE(" "); break;
                case '\n': WRITE("^"); break;
                case NEWLINE_IN_STRING: WRITE("^"); break;
                default: PUT(c);
            }
        }
    }

• This code is used in §8.

§8.3. Print mode is like value mode except that, for obscure implementation reasons inside the I6 compiler, @{40}, @{5E} and @{7E} cannot be used to escape those character codes, and instead the @@ decimal notation has to be used instead. But that can take a decimal value of arbitrary length and has no brace delimiters; so we must be careful not to encode ^1 as "@@941" because that would ask for character 941, not for character 94 and then a 1. Instead we encode it as "@@94@{31}", since the ASCII code for a digit 1 is 31 in hexadecimal.

Compile literal text in print-statement mode8.3 =

    int esc_char = FALSE;
    LOOP_THROUGH_TEXT(pos, S) {
        inchar32_t c = Str::get(pos);
        if (c >= 0x100) WRITE("@{%04x}", c);
        else {
            switch(c) {
                case '@': WRITE("@@64"); esc_char = TRUE; continue;
                case '"': WRITE("~"); break;
                case '^': WRITE("@@94"); esc_char = TRUE; continue;
                case '~': WRITE("@@126"); esc_char = TRUE; continue;
                case '\\': WRITE("@{5C}"); break;
                case '\t': WRITE(" "); break;
                case '\n': WRITE("^"); break;
                case NEWLINE_IN_STRING: WRITE("^"); break;
                default: {
                    if (esc_char) WRITE("@{%02x}", c);
                    else PUT(c);
                }
            }
        }
        esc_char = FALSE;
    }

• This code is used in §8.

§9. Finally, names of constants are compiled just as themselves:

void I6TargetConstants::compile_literal_symbol?Usage of I6TargetConstants::compile_literal_symbol:
§1, §3.1(code_generator *gtr, code_generation *gen,
    inter_symbol *A) {
    text_stream *OUT = CodeGen::current(gen);
    WRITE("%S", InterSymbol::trans(A));
}