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2a3f68d2c42d7892ee38e715e4632c87aab0ef94
akbasic/src/verbs.c
Andrew Kesterson 2a3f68d2c4 Add strict pointers: AS PTR TO, POINT ... AT, and the -> operator 
A pointer is a distinct declared kind rather than a mode a structure can be in,
which is what "strict" means here: `.` requires a structure on its left and `->`
requires a pointer, neither stands in for the other, and both refusals name the
operator the program should have used. So a reader always knows from the
spelling whether the thing on the left is their own copy or somebody else's
data.

Assignment still copies. POINT is the only way to share, so a program that never
writes it can never be surprised by aliasing -- and `P@ = A@` is refused with a
message saying to POINT it instead, rather than quietly becoming the one
assignment in the language that does not copy.

PTR TO is also the only way a TYPE may refer to itself, since by value it would
have no finite size. That is what makes a linked list possible, and
tests/language/structures/pointers.bas builds one, walks it and renders it.

Rendering follows pointers, so it needs a depth bound where copying does not:
copy stops at a pointer by construction, but two nodes pointing at each other is
easy to write and PRINT would not come back. Four levels, chosen so the bound
bites before the 256-byte render buffer does -- otherwise a cycle would stop
because it ran out of room rather than because it was told to.

Three things the work turned up, all now pinned by tests:

A freshly DIMmed record printed `(UNDEFINED STRING REPRESENTATION FOR 0)` for
every field. Slots now take the type their field declared, so it reads as zeros.

Adding POINT as a verb makes POINT unusable as a type name, and the parser
reported that as "Expected expression or literal" pointing at the line rather
than the problem. The prescan now refuses a reserved word as a type name and
says so.

Field names follow the same reserved-word rule as variable names, enforced by
the loader's own scan -- `TO@` is a bad field name for exactly the reason `TO#`
is a bad variable name. Recorded rather than worked around.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
2026-08-01 11:48:09 -04:00

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/**
* @file verbs.c
* @brief The dispatch table: every verb, function and reserved word in one place.
*/
#include <ctype.h>
#include <stdlib.h>
#include <string.h>
#include <akerror.h>
#include <akbasic/error.h>
#include <akbasic/verbs.h>
#include "verbs.h"
/*
* Sorted by name so bsearch() is valid -- tests/verbs_table.c asserts the
* ordering, because a mis-sorted row silently becomes an unfindable verb rather
* than a compile error.
*
* A NULL parse handler means the rval parses as a plain expression. A NULL exec
* handler means the token is consumed by some other verb's parse handler and is
* never evaluated on its own: ELSE, STEP, THEN and TO are all in that class, as
* are the four reserved words, which exist here only so the scanner can give
* them their token type.
*
* The reference bootstraps MOD, SPC and STR by running a BASIC program of DEF
* statements through the interpreter at startup and keeping their expressions
* (basicruntime_functions.go:14). That hack is not reproduced: they are ordinary
* native handlers here, which removes the need to run the interpreter before the
* interpreter is ready.
*/
static const akbasic_Verb VERBS[] = {
/* name token type arity parse handler exec handler */
{ "ABS", AKBASIC_TOK_FUNCTION, 1, NULL, akbasic_fn_abs },
{ "AND", AKBASIC_TOK_AND, -1, NULL, NULL },
{ "APPEND", AKBASIC_TOK_COMMAND, -1, akbasic_parse_arglist, akbasic_cmd_append },
{ "ATN", AKBASIC_TOK_FUNCTION, 1, NULL, akbasic_fn_atn },
{ "AUTO", AKBASIC_TOK_COMMAND_IMMEDIATE, -1, NULL, akbasic_cmd_auto },
{ "BACKUP", AKBASIC_TOK_COMMAND, -1, akbasic_parse_optional_arglist, akbasic_cmd_backup },
{ "BEGIN", AKBASIC_TOK_COMMAND, -1, NULL, akbasic_cmd_begin },
{ "BEND", AKBASIC_TOK_COMMAND, -1, NULL, akbasic_cmd_bend },
{ "BLOAD", AKBASIC_TOK_COMMAND, -1, akbasic_parse_arglist, akbasic_cmd_bload },
{ "BOOT", AKBASIC_TOK_COMMAND, -1, akbasic_parse_optional_arglist, akbasic_cmd_boot },
{ "BOX", AKBASIC_TOK_COMMAND, -1, akbasic_parse_arglist, akbasic_cmd_box },
{ "BSAVE", AKBASIC_TOK_COMMAND, -1, akbasic_parse_arglist, akbasic_cmd_bsave },
{ "BUMP", AKBASIC_TOK_FUNCTION, 1, NULL, akbasic_fn_bump },
{ "CATALOG", AKBASIC_TOK_COMMAND_IMMEDIATE, -1, akbasic_parse_optional_arglist, akbasic_cmd_directory },
{ "CHAR", AKBASIC_TOK_COMMAND, -1, akbasic_parse_arglist, akbasic_cmd_char },
{ "CHR", AKBASIC_TOK_FUNCTION, 1, NULL, akbasic_fn_chr },
{ "CIRCLE", AKBASIC_TOK_COMMAND, -1, akbasic_parse_arglist, akbasic_cmd_circle },
{ "CLR", AKBASIC_TOK_COMMAND, -1, NULL, akbasic_cmd_clr },
{ "COLLECT", AKBASIC_TOK_COMMAND, -1, akbasic_parse_optional_arglist, akbasic_cmd_collect },
{ "COLLISION", AKBASIC_TOK_COMMAND, -1, akbasic_parse_arglist, akbasic_cmd_collision },
{ "COLOR", AKBASIC_TOK_COMMAND, -1, akbasic_parse_arglist, akbasic_cmd_color },
{ "CONCAT", AKBASIC_TOK_COMMAND, -1, akbasic_parse_arglist, akbasic_cmd_concat },
{ "CONT", AKBASIC_TOK_COMMAND_IMMEDIATE, -1, NULL, akbasic_cmd_cont },
{ "COPY", AKBASIC_TOK_COMMAND, -1, akbasic_parse_arglist, akbasic_cmd_copy },
{ "COS", AKBASIC_TOK_FUNCTION, 1, NULL, akbasic_fn_cos },
{ "DATA", AKBASIC_TOK_COMMAND, -1, akbasic_parse_data, akbasic_cmd_data },
{ "DCLEAR", AKBASIC_TOK_COMMAND, -1, akbasic_parse_optional_arglist, akbasic_cmd_dclear },
{ "DCLOSE", AKBASIC_TOK_COMMAND, -1, akbasic_parse_optional_arglist, akbasic_cmd_dclose },
{ "DEF", AKBASIC_TOK_COMMAND, -1, akbasic_parse_def, akbasic_cmd_def },
{ "DELETE", AKBASIC_TOK_COMMAND_IMMEDIATE, -1, NULL, akbasic_cmd_delete },
{ "DIM", AKBASIC_TOK_COMMAND, -1, akbasic_parse_dim, akbasic_cmd_dim },
{ "DIRECTORY", AKBASIC_TOK_COMMAND_IMMEDIATE, -1, akbasic_parse_optional_arglist, akbasic_cmd_directory },
{ "DLOAD", AKBASIC_TOK_COMMAND_IMMEDIATE, -1, NULL, akbasic_cmd_dload },
{ "DO", AKBASIC_TOK_COMMAND, -1, akbasic_parse_do, akbasic_cmd_do },
{ "DOPEN", AKBASIC_TOK_COMMAND, -1, akbasic_parse_arglist, akbasic_cmd_dopen },
{ "DRAW", AKBASIC_TOK_COMMAND, -1, akbasic_parse_draw, akbasic_cmd_draw },
{ "DSAVE", AKBASIC_TOK_COMMAND_IMMEDIATE, -1, NULL, akbasic_cmd_dsave },
{ "DVERIFY", AKBASIC_TOK_COMMAND_IMMEDIATE, -1, akbasic_parse_arglist, akbasic_cmd_dverify },
{ "ELSE", AKBASIC_TOK_COMMAND, -1, NULL, NULL },
{ "END", AKBASIC_TOK_COMMAND, -1, NULL, akbasic_cmd_end },
{ "ENVELOPE", AKBASIC_TOK_COMMAND, -1, akbasic_parse_arglist, akbasic_cmd_envelope },
{ "ERR", AKBASIC_TOK_FUNCTION, 1, NULL, akbasic_fn_err },
{ "EXIT", AKBASIC_TOK_COMMAND, -1, NULL, akbasic_cmd_exit },
{ "FETCH", AKBASIC_TOK_COMMAND, -1, akbasic_parse_arglist, akbasic_cmd_fetch },
{ "FILTER", AKBASIC_TOK_COMMAND, -1, akbasic_parse_arglist, akbasic_cmd_filter },
{ "FOR", AKBASIC_TOK_COMMAND, -1, akbasic_parse_for, akbasic_cmd_for },
{ "GET", AKBASIC_TOK_COMMAND, -1, NULL, akbasic_cmd_get },
{ "GETKEY", AKBASIC_TOK_COMMAND, -1, NULL, akbasic_cmd_getkey },
{ "GOSUB", AKBASIC_TOK_COMMAND, -1, NULL, akbasic_cmd_gosub },
{ "GOTO", AKBASIC_TOK_COMMAND, -1, NULL, akbasic_cmd_goto },
{ "GRAPHIC", AKBASIC_TOK_COMMAND, -1, akbasic_parse_arglist, akbasic_cmd_graphic },
{ "GSHAPE", AKBASIC_TOK_COMMAND, -1, akbasic_parse_arglist, akbasic_cmd_gshape },
{ "HEADER", AKBASIC_TOK_COMMAND, -1, akbasic_parse_optional_arglist, akbasic_cmd_header },
{ "HELP", AKBASIC_TOK_COMMAND_IMMEDIATE, -1, NULL, akbasic_cmd_help },
{ "HEX", AKBASIC_TOK_FUNCTION, 1, NULL, akbasic_fn_hex },
{ "IF", AKBASIC_TOK_COMMAND, -1, akbasic_parse_if, akbasic_cmd_if },
{ "INPUT", AKBASIC_TOK_COMMAND, -1, akbasic_parse_input, akbasic_cmd_input },
/*
* `INPUT#` and `PRINT#` are never scanned as verb names -- the scanner reads
* a `#` as a type suffix and refuses a verb carrying one -- so these rows are
* reached only from akbasic_parse_input() and akbasic_parse_print(), which
* build a leaf with the name directly. They still have to be here, and in
* order, because dispatch is a bsearch on the leaf's name.
*/
{ "INPUT#", AKBASIC_TOK_COMMAND, -1, NULL, akbasic_cmd_input_channel },
{ "INSTR", AKBASIC_TOK_FUNCTION, 2, NULL, akbasic_fn_instr },
{ "KEY", AKBASIC_TOK_COMMAND, -1, akbasic_parse_optional_arglist, akbasic_cmd_key },
{ "LABEL", AKBASIC_TOK_COMMAND, -1, akbasic_parse_label, akbasic_cmd_label },
{ "LEFT", AKBASIC_TOK_FUNCTION, 2, NULL, akbasic_fn_left },
{ "LEN", AKBASIC_TOK_FUNCTION, 1, NULL, akbasic_fn_len },
{ "LET", AKBASIC_TOK_COMMAND, -1, akbasic_parse_let, akbasic_cmd_let },
{ "LIST", AKBASIC_TOK_COMMAND_IMMEDIATE, -1, NULL, akbasic_cmd_list },
{ "LOAD", AKBASIC_TOK_COMMAND_IMMEDIATE, -1, NULL, akbasic_cmd_dload },
{ "LOCATE", AKBASIC_TOK_COMMAND, -1, akbasic_parse_arglist, akbasic_cmd_locate },
{ "LOG", AKBASIC_TOK_FUNCTION, 1, NULL, akbasic_fn_log },
{ "LOOP", AKBASIC_TOK_COMMAND, -1, akbasic_parse_loop, akbasic_cmd_loop },
{ "MID", AKBASIC_TOK_FUNCTION, 3, NULL, akbasic_fn_mid },
{ "MOD", AKBASIC_TOK_FUNCTION, 2, NULL, akbasic_fn_mod },
{ "MOVSPR", AKBASIC_TOK_COMMAND, -1, akbasic_parse_movspr, akbasic_cmd_movspr },
{ "NEW", AKBASIC_TOK_COMMAND_IMMEDIATE, -1, NULL, akbasic_cmd_new },
{ "NEXT", AKBASIC_TOK_COMMAND, -1, NULL, akbasic_cmd_next },
{ "NOT", AKBASIC_TOK_NOT, -1, NULL, NULL },
{ "ON", AKBASIC_TOK_COMMAND, -1, akbasic_parse_on, akbasic_cmd_on },
{ "OR", AKBASIC_TOK_OR, -1, NULL, NULL },
{ "PAINT", AKBASIC_TOK_COMMAND, -1, akbasic_parse_arglist, akbasic_cmd_paint },
{ "PEEK", AKBASIC_TOK_FUNCTION, 1, NULL, akbasic_fn_peek },
{ "PLAY", AKBASIC_TOK_COMMAND, -1, NULL, akbasic_cmd_play },
{ "POINT", AKBASIC_TOK_COMMAND, -1, akbasic_parse_point, akbasic_cmd_point },
{ "POINTER", AKBASIC_TOK_FUNCTION, 1, NULL, akbasic_fn_pointer },
{ "POINTERVAR", AKBASIC_TOK_FUNCTION, 1, NULL, akbasic_fn_pointervar },
{ "POKE", AKBASIC_TOK_COMMAND, -1, akbasic_parse_poke, akbasic_cmd_poke },
{ "PRINT", AKBASIC_TOK_COMMAND, -1, akbasic_parse_print, akbasic_cmd_print },
{ "PRINT#", AKBASIC_TOK_COMMAND, -1, NULL, akbasic_cmd_print_channel },
{ "PUDEF", AKBASIC_TOK_COMMAND, -1, NULL, akbasic_cmd_pudef },
{ "QUIT", AKBASIC_TOK_COMMAND_IMMEDIATE, -1, NULL, akbasic_cmd_quit },
{ "RAD", AKBASIC_TOK_FUNCTION, 1, NULL, akbasic_fn_rad },
{ "READ", AKBASIC_TOK_COMMAND, -1, akbasic_parse_read, akbasic_cmd_read },
{ "RECORD", AKBASIC_TOK_COMMAND, -1, akbasic_parse_arglist, akbasic_cmd_record },
{ "REM", AKBASIC_TOK_REM, -1, NULL, NULL },
{ "RENAME", AKBASIC_TOK_COMMAND, -1, akbasic_parse_arglist, akbasic_cmd_rename },
{ "RENUMBER", AKBASIC_TOK_COMMAND_IMMEDIATE, -1, akbasic_parse_optional_arglist, akbasic_cmd_renumber },
{ "RESTORE", AKBASIC_TOK_COMMAND, -1, NULL, akbasic_cmd_restore },
{ "RESUME", AKBASIC_TOK_COMMAND, -1, akbasic_parse_resume, akbasic_cmd_resume },
{ "RETURN", AKBASIC_TOK_COMMAND, -1, NULL, akbasic_cmd_return },
{ "RGR", AKBASIC_TOK_FUNCTION, 1, NULL, akbasic_fn_rgr },
{ "RIGHT", AKBASIC_TOK_FUNCTION, 2, NULL, akbasic_fn_right },
{ "RSPCOLOR", AKBASIC_TOK_FUNCTION, 1, NULL, akbasic_fn_rspcolor },
{ "RSPPOS", AKBASIC_TOK_FUNCTION, 2, NULL, akbasic_fn_rsppos },
{ "RSPRITE", AKBASIC_TOK_FUNCTION, 2, NULL, akbasic_fn_rsprite },
{ "RUN", AKBASIC_TOK_COMMAND_IMMEDIATE, -1, NULL, akbasic_cmd_run },
{ "SAVE", AKBASIC_TOK_COMMAND_IMMEDIATE, -1, NULL, akbasic_cmd_dsave },
{ "SCALE", AKBASIC_TOK_COMMAND, -1, akbasic_parse_arglist, akbasic_cmd_scale },
{ "SCNCLR", AKBASIC_TOK_COMMAND, -1, NULL, akbasic_cmd_scnclr },
{ "SCRATCH", AKBASIC_TOK_COMMAND, -1, akbasic_parse_arglist, akbasic_cmd_scratch },
{ "SGN", AKBASIC_TOK_FUNCTION, 1, NULL, akbasic_fn_sgn },
{ "SHL", AKBASIC_TOK_FUNCTION, 2, NULL, akbasic_fn_shl },
{ "SHR", AKBASIC_TOK_FUNCTION, 2, NULL, akbasic_fn_shr },
{ "SIN", AKBASIC_TOK_FUNCTION, 1, NULL, akbasic_fn_sin },
{ "SLEEP", AKBASIC_TOK_COMMAND, -1, akbasic_parse_arglist, akbasic_cmd_sleep },
{ "SOUND", AKBASIC_TOK_COMMAND, -1, akbasic_parse_arglist, akbasic_cmd_sound },
{ "SPC", AKBASIC_TOK_FUNCTION, 1, NULL, akbasic_fn_spc },
{ "SPRCOLOR", AKBASIC_TOK_COMMAND, -1, akbasic_parse_arglist, akbasic_cmd_sprcolor },
{ "SPRITE", AKBASIC_TOK_COMMAND, -1, akbasic_parse_arglist, akbasic_cmd_sprite },
{ "SPRSAV", AKBASIC_TOK_COMMAND, -1, akbasic_parse_arglist, akbasic_cmd_sprsav },
{ "SSHAPE", AKBASIC_TOK_COMMAND, -1, akbasic_parse_arglist, akbasic_cmd_sshape },
{ "STASH", AKBASIC_TOK_COMMAND, -1, akbasic_parse_arglist, akbasic_cmd_stash },
{ "STEP", AKBASIC_TOK_COMMAND, -1, NULL, NULL },
{ "STOP", AKBASIC_TOK_COMMAND, -1, NULL, akbasic_cmd_stop },
{ "STR", AKBASIC_TOK_FUNCTION, 1, NULL, akbasic_fn_str },
{ "SWAP", AKBASIC_TOK_COMMAND, -1, akbasic_parse_arglist, akbasic_cmd_swap },
{ "SYS", AKBASIC_TOK_COMMAND, -1, akbasic_parse_arglist, akbasic_cmd_sys },
{ "TAN", AKBASIC_TOK_FUNCTION, 1, NULL, akbasic_fn_tan },
{ "TEMPO", AKBASIC_TOK_COMMAND, -1, akbasic_parse_arglist, akbasic_cmd_tempo },
{ "THEN", AKBASIC_TOK_COMMAND, -1, NULL, NULL },
{ "TO", AKBASIC_TOK_COMMAND, -1, NULL, NULL },
{ "TRAP", AKBASIC_TOK_COMMAND, -1, NULL, akbasic_cmd_trap },
{ "TROFF", AKBASIC_TOK_COMMAND, -1, NULL, akbasic_cmd_troff },
{ "TRON", AKBASIC_TOK_COMMAND, -1, NULL, akbasic_cmd_tron },
{ "TYPE", AKBASIC_TOK_COMMAND, -1, akbasic_parse_type, akbasic_cmd_type },
{ "UNTIL", AKBASIC_TOK_COMMAND, -1, NULL, NULL },
{ "USING", AKBASIC_TOK_COMMAND, -1, NULL, NULL },
{ "VAL", AKBASIC_TOK_FUNCTION, 1, NULL, akbasic_fn_val },
{ "VERIFY", AKBASIC_TOK_COMMAND_IMMEDIATE, -1, akbasic_parse_arglist, akbasic_cmd_dverify },
{ "VOL", AKBASIC_TOK_COMMAND, -1, akbasic_parse_arglist, akbasic_cmd_vol },
{ "WAIT", AKBASIC_TOK_COMMAND, -1, akbasic_parse_arglist, akbasic_cmd_wait },
{ "WHILE", AKBASIC_TOK_COMMAND, -1, NULL, NULL },
{ "WIDTH", AKBASIC_TOK_COMMAND, -1, akbasic_parse_arglist, akbasic_cmd_width },
{ "WINDOW", AKBASIC_TOK_COMMAND, -1, akbasic_parse_arglist, akbasic_cmd_window },
{ "XOR", AKBASIC_TOK_FUNCTION, 2, NULL, akbasic_fn_xor },
};
#define VERB_COUNT ((int)(sizeof(VERBS) / sizeof(VERBS[0])))
static int verb_compare(const void *key, const void *element)
{
const akbasic_Verb *verb = (const akbasic_Verb *)element;
return strcmp((const char *)key, verb->name);
}
const akbasic_Verb *akbasic_verb_table(int *count)
{
if ( count != NULL ) {
*count = VERB_COUNT;
}
return VERBS;
}
akerr_ErrorContext *akbasic_verb_lookup(const char *name, const akbasic_Verb **dest)
{
PREPARE_ERROR(errctx);
char upper[AKBASIC_MAX_STRING_LENGTH];
size_t i = 0;
size_t len = 0;
FAIL_ZERO_RETURN(errctx, (name != NULL), AKERR_NULLPOINTER, "NULL name in verb lookup");
FAIL_ZERO_RETURN(errctx, (dest != NULL), AKERR_NULLPOINTER, "NULL destination in verb lookup");
*dest = NULL;
len = strlen(name);
if ( len == 0 || len >= sizeof(upper) ) {
/* Too long to be any verb we know. Not an error, just a miss. */
SUCCEED_RETURN(errctx);
}
for ( i = 0; i < len; i++ ) {
upper[i] = (char)toupper((unsigned char)name[i]);
}
upper[len] = '\0';
*dest = (const akbasic_Verb *)bsearch(upper, VERBS, VERB_COUNT, sizeof(VERBS[0]), verb_compare);
SUCCEED_RETURN(errctx);
}
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