Two consecutive bytecode words are used to store a single value in binary Inter.

• §2. Pairs
• §4. Numeric pairs
• §6. Textual pairs
• §8. Real pairs
• §11. Dictionary word pairs
• §13. Symbolic pairs
• §15. Glob pairs
• §17. The undef pair
• §19. Pairs in bytecode
• §21. Transposition
• §22. Verification

§1. About time to define the types we're using to represent Inter words in C. It turns out to be more convenient to define these by what amounts to #define than to use typedef.

define inter_ti unsigned int
define signed_inter_ti int

§2. Pairs. A constant value in Inter code is represented by a pair of inter_ti values: the format and the content.

typedef struct inter_pair {
    inter_ti data_format;  one of the *_IVAL values below
    inter_ti data_content;
} inter_pair;

• The structure inter_pair is private to this section.

§3. These are the formats. Note that changing any of these values would invalidate existing Inter binary files, necessitating a bump of The Inter Version.

enum DECIMAL_IVAL from 0x10000
enum HEX_IVAL
enum BINARY_IVAL
enum SIGNED_IVAL
enum TEXTUAL_IVAL
enum REAL_IVAL
enum DWORD_IVAL
enum PDWORD_IVAL
enum SYMBOLIC_IVAL
enum GLOB_IVAL
enum UNDEF_IVAL

§4. Numeric pairs. These can represent any inter_ti value, and are used when the data is a literal integer. Note that they express both an integer and also a preferred way to print it out — as decimal, hexadecimal, binary, or signed decimal. But these are all numerically equal. They affect only the way in which the Inter program is printed to text files, not the meaning of the program.

inter_pair InterValuePairs::number?Usage of InterValuePairs::number:
The Constant Construct - §11
The Instance Construct - §3(inter_ti N) {
    inter_pair pair;
    pair.data_format = DECIMAL_IVAL;
    pair.data_content = N;
    return pair;
}

inter_pair InterValuePairs::number_in_base?Usage of InterValuePairs::number_in_base:
Inter in Text Files - §12.2(inter_ti N, unsigned int b) {
    inter_pair pair;
    switch (b) {
        case 2: pair.data_format = BINARY_IVAL; break;
        case 10: pair.data_format = DECIMAL_IVAL; break;
        case 16: pair.data_format = HEX_IVAL; break;
        default: internal_error("only bases 2, 10, 16 are supported");
    }
    pair.data_content = N;
    return pair;
}

inter_pair InterValuePairs::signed_number?Usage of InterValuePairs::signed_number:
Inter in Text Files - §12.2(int N) {
    inter_pair pair;
    pair.data_format = SIGNED_IVAL;
    pair.data_content = (inter_ti) N;
    return pair;
}

inter_pair InterValuePairs::number_from_I6_notation(text_stream *S) {
    int sign = 1, from = 0;
    unsigned int base = 10;
    if (Str::prefix_eq(S, I"-", 1)) { sign = -1; from = 1; }
    if (Str::prefix_eq(S, I"$", 1)) { base = 16; from = 1; }
    if (Str::prefix_eq(S, I"$$", 2)) { base = 2; from = 2; }
    long long int N = 0;
    LOOP_THROUGH_TEXT(pos, S) {
        if (pos.index < from) continue;
        inchar32_t c = Str::get(pos), d = 0;
        if ((c >= 'a') && (c <= 'z')) d = c-'a'+10;
        else if ((c >= 'A') && (c <= 'Z')) d = c-'A'+10;
        else if ((c >= '0') && (c <= '9')) d = c-'0';
        else return InterValuePairs::undef();
        if (d >= base) return InterValuePairs::undef();
        N = base*N + (long long int) d;
        if (pos.index > 34) return InterValuePairs::undef();
    }
    return InterValuePairs::number((inter_ti) (sign*N));
}

inter_ti InterValuePairs::to_number?Usage of InterValuePairs::to_number:
Inter in Text Files - §12.1
Metadata - §4.1
The Constant Construct - §10(inter_pair pair) {
    if (InterValuePairs::is_number(pair)) return pair.data_content;
    return 0;
}

inter_ti InterValuePairs::to_base?Usage of InterValuePairs::to_base:
Inter in Text Files - §12.1(inter_pair pair) {
    switch (pair.data_format) {
        case DECIMAL_IVAL: return 10;
        case SIGNED_IVAL: return 10;
        case HEX_IVAL: return 16;
        case BINARY_IVAL: return 2;
    }
    return 0;
}

§5. Testing:

int InterValuePairs::is_number?Usage of InterValuePairs::is_number:
§4, §22
Inter in Text Files - §12
Metadata - §4.1
The Constant Construct - §10, §11(inter_pair pair) {
    if ((pair.data_format == DECIMAL_IVAL) ||
        (pair.data_format == HEX_IVAL) ||
        (pair.data_format == BINARY_IVAL) ||
        (pair.data_format == SIGNED_IVAL))
        return TRUE;
    return FALSE;
}

int InterValuePairs::is_one(inter_pair pair) {
    if ((InterValuePairs::is_number(pair)) &&
        (pair.data_content == 1)) return TRUE;
    return FALSE;
}

int InterValuePairs::is_zero(inter_pair pair) {
    if ((InterValuePairs::is_number(pair)) &&
        (pair.data_content == 0)) return TRUE;
    return FALSE;
}

§6. Textual pairs. These can represent an arbitrarily long literal string of text.

inter_pair InterValuePairs::from_text?Usage of InterValuePairs::from_text:
Inter in Text Files - §12.4(inter_bookmark *IBM, text_stream *text) {
    inter_tree *I = InterBookmark::tree(IBM);
    inter_package *pack = InterBookmark::package(IBM);
    inter_ti ID = InterWarehouse::create_text(InterTree::warehouse(I), pack);
    text_stream *text_storage = InterWarehouse::get_text(InterTree::warehouse(I), ID);
    Str::copy(text_storage, text);
    inter_pair pair;
    pair.data_format = TEXTUAL_IVAL;
    pair.data_content = ID;
    return pair;
}

text_stream *InterValuePairs::to_text?Usage of InterValuePairs::to_text:
Inter in Text Files - §12.3
Metadata - §6.1(inter_tree *I, inter_pair pair) {
    if (InterValuePairs::is_text(pair))
        return InterWarehouse::get_text(InterTree::warehouse(I), pair.data_content);
    return NULL;
}

§7. Testing:

int InterValuePairs::is_text?Usage of InterValuePairs::is_text:
§6
Inter in Text Files - §12
Metadata - §6.1(inter_pair pair) {
    if (pair.data_format == TEXTUAL_IVAL) return TRUE;
    return FALSE;
}

§8. Real pairs. These represent real numbers, but they do so by storing them as literal strings prefaced by a sign character, + or -.

Though the argument here has type double, we are not guaranteeing that level of service, and in fact these are likely to be no better than float precision on some platforms.

inter_pair InterValuePairs::real(inter_bookmark *IBM, double g) {
    inter_tree *I = InterBookmark::tree(IBM);
    inter_package *pack = InterBookmark::package(IBM);
    inter_ti ID = InterWarehouse::create_text(InterTree::warehouse(I), pack);
    text_stream *text_storage = InterWarehouse::get_text(InterTree::warehouse(I), ID);
    if (g > 0) WRITE_TO(text_storage, "+");
    WRITE_TO(text_storage, "%g", g);
    inter_pair pair;
    pair.data_format = REAL_IVAL;
    pair.data_content = ID;
    return pair;
}

§9. Inform 6 notation begins with a dollar $ — for example, $+3.1415 — but otherwise is similar.

inter_pair InterValuePairs::real_from_I6_notation?Usage of InterValuePairs::real_from_I6_notation:
Inter in Text Files - §12.6(inter_bookmark *IBM, text_stream *S) {
    inter_tree *I = InterBookmark::tree(IBM);
    inter_package *pack = InterBookmark::package(IBM);
    inter_ti ID = InterWarehouse::create_text(InterTree::warehouse(I), pack);
    text_stream *text_storage = InterWarehouse::get_text(InterTree::warehouse(I), ID);
    LOOP_THROUGH_TEXT(pos, S)
        if (Str::get(pos) != '$')
            PUT_TO(text_storage, Str::get(pos));
    inter_pair pair;
    pair.data_format = REAL_IVAL;
    pair.data_content = ID;
    return pair;
}

text_stream *InterValuePairs::to_textual_real?Usage of InterValuePairs::to_textual_real:
Inter in Text Files - §12.5(inter_tree *I, inter_pair pair) {
    if (InterValuePairs::is_real(pair))
        return InterWarehouse::get_text(InterTree::warehouse(I), pair.data_content);
    return NULL;
}

§10. Testing:

int InterValuePairs::is_real?Usage of InterValuePairs::is_real:
§9
Inter in Text Files - §12(inter_pair pair) {
    if (pair.data_format == REAL_IVAL) return TRUE;
    return FALSE;
}

§11. Dictionary word pairs. These are relevant only to command-parser IF projects, and none of these values otherwise ever exist. They exist in two forms, one marked as possibly plural, the other not so marked. Just because a word is marked plural, it doesn't follow that every usage of it will be in a plural noun context: so "singular" here is best read as "no comment on the number of this if it is used in a noun context".

It would be appealing to remove these from the design of Inter, but that's harder than it seems. Dictionary words have semantics which are hard to imitate with other values which would be legal in a constant context.

inter_pair InterValuePairs::from_singular_dword?Usage of InterValuePairs::from_singular_dword:
Inter in Text Files - §12.8(inter_bookmark *IBM, text_stream *word) {
    inter_tree *I = InterBookmark::tree(IBM);
    inter_package *pack = InterBookmark::package(IBM);
    inter_ti ID = InterWarehouse::create_text(InterTree::warehouse(I), pack);
    text_stream *text_storage = InterWarehouse::get_text(InterTree::warehouse(I), ID);
    Str::copy(text_storage, word);
    inter_pair pair;
    pair.data_format = DWORD_IVAL;
    pair.data_content = ID;
    return pair;
}

inter_pair InterValuePairs::from_plural_dword?Usage of InterValuePairs::from_plural_dword:
Inter in Text Files - §12.10(inter_bookmark *IBM, text_stream *word) {
    inter_tree *I = InterBookmark::tree(IBM);
    inter_package *pack = InterBookmark::package(IBM);
    inter_ti ID = InterWarehouse::create_text(InterTree::warehouse(I), pack);
    text_stream *text_storage = InterWarehouse::get_text(InterTree::warehouse(I), ID);
    Str::copy(text_storage, word);
    inter_pair pair;
    pair.data_format = PDWORD_IVAL;
    pair.data_content = ID;
    return pair;
}

text_stream *InterValuePairs::to_dictionary_word?Usage of InterValuePairs::to_dictionary_word:
Inter in Text Files - §12.7, §12.9(inter_tree *I, inter_pair pair) {
    if (InterValuePairs::is_dword(pair))
        return InterWarehouse::get_text(InterTree::warehouse(I), pair.data_content);
    return NULL;
}

§12. Testing:

int InterValuePairs::is_dword?Usage of InterValuePairs::is_dword:
§11(inter_pair pair) {
    if ((pair.data_format == DWORD_IVAL) || (pair.data_format == PDWORD_IVAL)) return TRUE;
    return FALSE;
}

int InterValuePairs::is_singular_dword?Usage of InterValuePairs::is_singular_dword:
Inter in Text Files - §12(inter_pair pair) {
    if (pair.data_format == DWORD_IVAL) return TRUE;
    return FALSE;
}

int InterValuePairs::is_plural_dword?Usage of InterValuePairs::is_plural_dword:
Inter in Text Files - §12(inter_pair pair) {
    if (pair.data_format == PDWORD_IVAL) return TRUE;
    return FALSE;
}

§13. Symbolic pairs. All other pairs represent known literal values, but a symbolic pair delegates that by saying "it's the value of this symbol". For example, a symbolic pair could mean "whatever the value of WORDSIZE is". Note that this symbol might not even be defined in the current Inter tree: it could be wired to a plug, which expects to find a definition in some other tree when linking takes place.

inter_pair InterValuePairs::symbolic?Usage of InterValuePairs::symbolic:
Inter in Text Files - §12.14, §12.14.1
The Val Construct - §4(inter_bookmark *IBM, inter_symbol *S) {
    return InterValuePairs::symbolic_in(InterBookmark::package(IBM), S);
}

inter_pair InterValuePairs::symbolic_in(inter_package *pack, inter_symbol *S) {
    inter_tree *I = InterPackage::tree(pack);
    if (S == NULL) internal_error("no symbol");
    inter_pair pair;
    pair.data_format = SYMBOLIC_IVAL;
    pair.data_content = InterSymbolsTable::id_from_symbol(I, pack, S);
    return pair;
}

inter_symbol *InterValuePairs::to_symbol?Usage of InterValuePairs::to_symbol:
The Constant Construct - §10, §11(inter_pair pair, inter_symbols_table *T) {
    if (InterValuePairs::is_symbolic(pair))
        return InterSymbolsTable::symbol_from_ID(T, pair.data_content);
    return NULL;
}

inter_symbol *InterValuePairs::to_symbol_not_following?Usage of InterValuePairs::to_symbol_not_following:
Inter in Text Files - §12.13(inter_pair pair, inter_symbols_table *T) {
    if (InterValuePairs::is_symbolic(pair))
        return InterSymbolsTable::symbol_from_ID_not_following(T, pair.data_content);
    return NULL;
}

inter_symbol *InterValuePairs::to_symbol_in?Usage of InterValuePairs::to_symbol_in:
Metadata - §5.1(inter_pair pair, inter_package *pack) {
    return InterValuePairs::to_symbol(pair, InterPackage::scope(pack));
}

inter_symbol *InterValuePairs::to_symbol_at?Usage of InterValuePairs::to_symbol_at:
The Constant Construct - §9(inter_pair pair, inter_tree_node *P) {
    return InterValuePairs::to_symbol(pair, InterPackage::scope_of(P));
}

§14. Testing:

int InterValuePairs::is_symbolic?Usage of InterValuePairs::is_symbolic:
§13
Inter in Text Files - §12
Metadata - §5.1
The Constant Construct - §9, §10, §11(inter_pair pair) {
    if (pair.data_format == SYMBOLIC_IVAL) return TRUE;
    return FALSE;
}

§15. Glob pairs. Globs are a desperation measure. They represent a value, but which is expressed in terms of raw source code which will produce that value. For instance, if you knew your Inter code would be compiled to C, you could have a glob of "time(0)", but of course this wouldn't work in compiled in a constant context, and wouldn't work if the Inter were aimed at any other final code-generator than C.

Globs were needed in the development stages of Inter but are now never produced anywhere in the Inter tool chain except in response to the textual Inter notation below. They cling on here just in case they are needed again.

inter_pair InterValuePairs::glob?Usage of InterValuePairs::glob:
Inter in Text Files - §12.12(inter_bookmark *IBM, text_stream *text) {
    inter_tree *I = InterBookmark::tree(IBM);
    inter_package *pack = InterBookmark::package(IBM);
    inter_ti ID = InterWarehouse::create_text(InterTree::warehouse(I), pack);
    text_stream *text_storage = InterWarehouse::get_text(InterTree::warehouse(I), ID);
    Str::copy(text_storage, text);
    inter_pair pair;
    pair.data_format = GLOB_IVAL;
    pair.data_content = ID;
    return pair;
}

text_stream *InterValuePairs::to_glob_text?Usage of InterValuePairs::to_glob_text:
Inter in Text Files - §12.11(inter_tree *I, inter_pair pair) {
    if (InterValuePairs::is_glob(pair))
        return InterWarehouse::get_text(InterTree::warehouse(I), pair.data_content);
    return NULL;
}

§16. Testing:

int InterValuePairs::is_glob?Usage of InterValuePairs::is_glob:
§15
Inter in Text Files - §12(inter_pair pair) {
    if (pair.data_format == GLOB_IVAL) return TRUE;
    return FALSE;
}

§17. The undef pair. There is just one undef pair. It means "undefined value", and allows functions which return inter_pair to signal that they couldn't work anything useful out. (See for example InterValuePairs::number_from_I6_notation above.)

inter_pair InterValuePairs::undef?Usage of InterValuePairs::undef:
§4
Inter in Text Files - §12.16
The Constant Construct - §6.2.1, §6.3, §8
The Instance Construct - §4, §6
The PropertyValue Construct - §4, §6
The Variable Construct - §4, §6
The Ref Construct - §4, §6
The Val Construct - §4, §6(void) {
    inter_pair pair;
    pair.data_format = UNDEF_IVAL;
    pair.data_content = 0;
    return pair;
}

§18. Testing:

int InterValuePairs::is_undef?Usage of InterValuePairs::is_undef:
Inter in Text Files - §12
The Instance Construct - §3(inter_pair pair) {
    if (pair.data_format == UNDEF_IVAL) return TRUE;
    return FALSE;
}

§19. Pairs in bytecode. In binary Inter, value pairs are always stored as consecutive fields in the bytecode of instructions. These fields should be read or written only with the following functions:

inter_pair InterValuePairs::get?Usage of InterValuePairs::get:
Verifying Inter - §11
The Constant Construct - §4, §7, §8, §9, §10, §11
The Instance Construct - §2, §3, §5, §6
The PropertyValue Construct - §2, §6
The Variable Construct - §2, §6
The Ref Construct - §6
The Val Construct - §2, §6(inter_tree_node *P, int field) {
    inter_pair pair;
    pair.data_format = P->W.instruction[field];
    pair.data_content = P->W.instruction[field+1];
    return pair;
}

void InterValuePairs::set?Usage of InterValuePairs::set:
The Constant Construct - §4, §8
The Instance Construct - §2, §3
The PropertyValue Construct - §2
The Variable Construct - §2
The Val Construct - §2(inter_tree_node *P, int field, inter_pair pair) {
    P->W.instruction[field] = pair.data_format;
    P->W.instruction[field+1] = pair.data_content;
}

§20. When creating new instructions, InterValuePairs::set cannot be used because the two words of a pair need to be supplied as two inter_ti values. For that purpose only, the following functions may be used:

inter_ti InterValuePairs::to_word1?Usage of InterValuePairs::to_word1:
The Constant Construct - §2
The Instance Construct - §2
The PropertyValue Construct - §2
The Variable Construct - §2
The Ref Construct - §2
The Val Construct - §2(inter_pair pair) {
    return pair.data_format;
}
inter_ti InterValuePairs::to_word2?Usage of InterValuePairs::to_word2:
The Constant Construct - §2
The Instance Construct - §2
The PropertyValue Construct - §2
The Variable Construct - §2
The Ref Construct - §2
The Val Construct - §2(inter_pair pair) {
    return pair.data_content;
}

§21. Transposition. See Inter in Binary Files for more on this. Basically the idea is that those pairs holding text or package resource ID numbers will need correction when read in from a binary Inter file (because in that process, resource ID numbers change).

inter_pair InterValuePairs::transpose?Usage of InterValuePairs::transpose:
The Constant Construct - §4
The Instance Construct - §2
The PropertyValue Construct - §2
The Variable Construct - §2
The Val Construct - §2(inter_pair pair, inter_ti *grid, inter_ti grid_extent,
    inter_error_message **E) {
    switch (pair.data_format) {
        case DWORD_IVAL:
        case PDWORD_IVAL:
        case TEXTUAL_IVAL:
        case REAL_IVAL:
        case GLOB_IVAL:
            pair.data_content = grid[pair.data_content];
            break;
    }
    return pair;
}

§22. Verification. Some minimal sanity checks on a pair, which can be performed quickly. There are numerous ways bad data could still pass this, but it will certainly catch random garbage, and doesn't take much time.

inter_error_message *InterValuePairs::verify?Usage of InterValuePairs::verify:
Verifying Inter - §11(inter_package *owner, inter_tree_node *P,
    inter_pair pair, inter_type type) {
    inter_symbols_table *scope = InterPackage::scope(owner);
    if (scope == NULL) scope = Inode::globals(P);
    if (InterValuePairs::is_number(pair)) Check this is in range for the type22.1
    switch (pair.data_format) {
        case SYMBOLIC_IVAL: Check this is reasonable, if we know what it is yet22.2;
        case DWORD_IVAL:
        case PDWORD_IVAL:
        case TEXTUAL_IVAL:
        case REAL_IVAL:
        case GLOB_IVAL:
        case UNDEF_IVAL:
            return NULL;
    }
    return Inode::error(P, I"value of unknown category", NULL);
}

§22.1. Check this is in range for the type22.1 =

    long long int I = (signed_inter_ti) pair.data_content;
    if (InterTypes::literal_is_in_range(I, type) == FALSE)
        return Inode::error(P, I"value out of range", NULL);
    return NULL;

• This code is used in §22.

§22.2. Check this is reasonable, if we know what it is yet22.2 =

    inter_symbol *symb = InterSymbolsTable::symbol_from_ID(scope, pair.data_content);
    if (symb == NULL) return Inode::error(P, I"no such symbol", NULL);
    if (InterSymbol::misc_but_undefined(symb)) return NULL;
    if (InterSymbol::defined_elsewhere(symb)) return NULL;
    if (InterTypes::expresses_value(symb) == FALSE)
        return Inode::error(P, I"nonconstant symbol", InterSymbol::identifier(symb));
    inter_type symbol_type = InterTypes::of_symbol(symb);
    return InterTypes::can_be_used_as(symbol_type, type,
        InterSymbol::identifier(symb), Inode::get_error_location(P));

• This code is used in §22.