mirror of
https://github.com/ctm/syn68k.git
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355 lines
8.9 KiB
C
355 lines
8.9 KiB
C
/*
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* macro.c
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*/
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#include "macro.h"
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#include "error.h"
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#include "token.h"
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/*
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#define DEBUG
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*/
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/* Private helper function. */
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static BOOL better_match (const List *ls, const List *new,const List *best);
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static void substitute_args (const List *argval, const List *argname,
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List *expr);
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/* This function replaces a given list with the macro expansion contained in
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* the symbol table. More than one macro with the same name may be defined;
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* the best match will be expanded (see heuristics, below.)
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*
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* A macro needn't be a function. (define my-favorite-number 7) is legal.
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*
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* A macro definition can contain any number of literals which must be
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* matched exactly in the invocation to be expanded (see heuristic 4 below.)
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* Additionally, variable numbers of arguments are supported. If the last
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* argument to a macro is "+tail", +tail will be shorthand for an arbitrarily
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* long list of arguments. For example, (define (foo x +tail)). Now
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* (foo north south east) will have x bound to "north", and tail bound to
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* "south east". Any subsequent usage of +tail will be exactly equivalent to
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* using the two words "south east"; it will be treated just like two
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* arguments.
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*
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* Here is an example that sums an arbitrarily long list of numbers:
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* (define (sum) 0)
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* (define (sum n +tail) (+ n (sum +tail)))
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*/
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BOOL
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macro_sub (List *ls, const SymbolTable *sym, BOOL flag_failure)
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{
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const Macro *m;
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List *best = NULL, *new, *op;
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SymbolInfo info;
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const char *name;
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#ifdef DEBUG
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printf ("macro_sub: "); print_list (ls, stdout); putchar ('\n');
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#endif
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/* Get the name of the macro to be expanded. */
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op = NULL;
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if (ls->token.type == TOK_LIST)
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{
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if (ls->car == NULL)
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{
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if (flag_failure)
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parse_error (ls, "Macro name is missing!\n");
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return FALSE;
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}
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if (ls->car->token.type == TOK_IDENTIFIER)
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name = ls->car->token.u.string;
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else
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{
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op = ls->car;
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name = NULL;
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}
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}
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else if (ls->token.type == TOK_IDENTIFIER)
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name = ls->token.u.string;
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else
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{
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op = ls;
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name = NULL;
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}
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/* Look up the macro list in the symbol table. */
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if (lookup_symbol (sym, name, &info, NULL) == HASH_NOTFOUND)
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{
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if (flag_failure)
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{
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char buf[1024];
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if (name == NULL)
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{
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if (op != NULL)
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parse_error (op, "Unknown operator \"%s\"\n",
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unparse_token (&op->token, buf));
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else
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parse_error (ls, "Unknown operator.\n");
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}
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else
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parse_error (ls, "Unknown operator \"%s\".\n", name);
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}
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return FALSE;
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}
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m = (const Macro *) info.p;
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/* Now we have a list of macros and we have to choose the best match by the
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* following heuristics, in order:
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* (1) Invocation form matching. "foo" and "(foo)" can only match
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* (define foo ...) and (define (foo) ...), respectively.
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* (2) The number of arguments must match. Note that the "+tail" construct
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* can allow an arbitrarily high number of arguments.
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* (3) All literals must match (see 3, below)
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* (4) Number of literal matches. For example, it is legal to both
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* (define (foo a1 a2 0) x) and (define (foo a1 a2 a3) y). In this
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* example, an invocation of (foo 2 1 0) would expand to x.
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* (5) Larger number of arguments. Whichever macro names the most arguments
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* (disregarding any "+tail", of course) will be preferred.
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* (6) Prefer the macro without a "+tail".
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* (7) Lexical predecence. In case of a tie, the first macro defined will
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* be chosen.
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*/
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/* Find the best match. */
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for (best = NULL; m != NULL; m = m->next)
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if (better_match (ls, m->expr, best))
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best = m->expr;
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/* Was there no match at all? */
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if (best == NULL)
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{
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if (flag_failure)
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parse_error (ls, "No applicable version of the \"%s\" macro exists "
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"for these arguments.\n", name);
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return FALSE;
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}
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/* Is this simple substitution (ie, no macro arguments, etc.) */
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if (ls->token.type != TOK_LIST)
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{
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if (best->cdr == NULL) /* Empty list? */
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ls->token.type = TOK_EMPTY;
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else if (CDDR (best) == NULL && best->cdr->token.type != TOK_LIST)
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{
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ls->token.type = best->cdr->token.type;
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ls->token.u = best->cdr->token.u;
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}
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else
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{
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new = copy_list (best->cdr);
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propagate_fileinfo (&ls->token, new); /* So we don't forget... */
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replace_list (ls, new);
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}
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return TRUE;
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}
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/* It's a complicate macro with arguments. Substitute in the arguments. */
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new = copy_list (best->cdr);
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substitute_args (CDAR (ls), CDAR (best), new);
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replace_list (ls, new);
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return TRUE;
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}
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static BOOL
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has_tail (const List *ls)
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{
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if (ls == NULL)
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return FALSE;
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while (ls->cdr != NULL)
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ls = ls->cdr;
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return (ls->token.type == TOK_TAIL);
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}
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#define IS_LITERAL(L) ((L)->token.type != TOK_IDENTIFIER \
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&& (L)->token.type != TOK_TAIL)
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static int
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count_literals (const List *ls)
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{
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int lit;
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for (lit = 0; ls != NULL; ls = ls->cdr)
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if (IS_LITERAL (ls))
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lit++;
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return lit;
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}
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/* Returns TRUE iff new is a better match than best according to the
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* heuristics above. If new is not legal, returns FALSE. best == NULL
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* is OK and is treated as the worst possible match (ie, any legal new beats
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* it.)
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*/
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static BOOL
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better_match (const List *ls, const List *new, const List *best)
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{
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BOOL new_has_tail, best_has_tail;
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int ls_length, new_length, best_length, new_lit, best_lit;
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const List *l1, *l2;
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#ifdef DEBUG
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printf ("ls = "); print_list (ls, stdout);
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printf (" new = "); print_list (new, stdout);
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putchar ('\n');
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#endif
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/* Heuristic (1) - must both be functions or not functions. */
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if (ls->token.type != new->token.type)
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return FALSE;
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/* If it's of the form (define foo 0), apply heuristic 6, since there
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* is only one kind of match.
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*/
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if (ls->token.type == TOK_IDENTIFIER)
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return (best == NULL);
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#ifdef DEBUG
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puts ("Passed h1");
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#endif
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/* Heuristic (2) - must have compatible #'s of arguments. */
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ls_length = list_length (ls->car);
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new_length = list_length (new->car);
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new_has_tail = has_tail (new->car);
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if ((ls_length > new_length && !new_has_tail) /* Too many args? */
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|| ls_length < new_length - new_has_tail) /* Too few? */
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return FALSE;
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#ifdef DEBUG
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puts ("Passed h2");
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#endif
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/* Heuristic (3) - all literals must match. */
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for (l1 = CDAR (ls), l2 = CDAR (new); l1 != NULL && l2 != NULL;
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l1 = l1->cdr, l2 = l2->cdr)
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{
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if (IS_LITERAL (l2))
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{
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if (!tokens_equal (&l1->token, &l2->token))
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return FALSE;
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}
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}
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/* At this point, new is legal. Therefore, if best == NULL, return TRUE. */
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if (best == NULL)
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return TRUE;
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#ifdef DEBUG
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puts ("Passed h3");
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#endif
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/* Heuristic (4) - number of literals. */
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new_lit = count_literals (new->car->cdr);
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best_lit = count_literals (best->car->cdr);
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if (new_lit != best_lit)
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return (new_lit > best_lit);
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#ifdef DEBUG
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puts ("Passed h4");
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#endif
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/* Heuristic (5) - number of arguments (not counting +tail). */
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best_has_tail = has_tail (best->car);
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best_length = list_length (best->car);
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if (new_length - new_has_tail != best_length - best_has_tail)
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return (new_length - new_has_tail > best_length - best_has_tail);
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#ifdef DEBUG
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puts ("Passed h5");
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#endif
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/* Heuristic (6) - prefer the macro without +tail. */
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if (best_has_tail ^ new_has_tail)
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return best_has_tail;
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#ifdef DEBUG
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puts ("Passed h6");
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#endif
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/* Heuristic (7) - recency. Assuming we process them in order... */
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return (best == NULL);
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}
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static void
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substitute_args (const List *argval, const List *argname, List *expr)
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{
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const List *name, *val, *tail = NULL;
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BOOL has_tail = FALSE;
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#ifdef DEBUG
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List *original_expr = expr;
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printf ("substitute_args: ");
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printf ("argval = "); print_list (argval, stdout);
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printf ("\nargname = "); print_list (argname, stdout);
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printf ("\nexpr = "); print_list (expr, stdout);
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putchar ('\n');
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#endif
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/* See if there is a +tail, and make it tail point to the list of args. */
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for (name = argname, val = argval; name != NULL;
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name = name->cdr, val = val->cdr)
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if (name->token.type == TOK_TAIL)
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{
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tail = val;
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has_tail = TRUE;
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break;
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}
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for (; expr != NULL; expr = expr->cdr)
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{
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switch (expr->token.type) {
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case TOK_LIST:
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substitute_args (argval, argname, expr->car);
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break;
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case TOK_IDENTIFIER:
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for (name = argname, val = argval; name != NULL && val != NULL;
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name = name->cdr, val = val->cdr)
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if (!IS_LITERAL (name) && tokens_equal (&name->token, &expr->token))
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{
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List *tmp_cdr = expr->cdr;
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*expr = *val;
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expr->car = copy_list (val->car);
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expr->cdr = tmp_cdr;
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break;
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}
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break;
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case TOK_TAIL:
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if (!has_tail)
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parse_error (expr, "But this macro has no tail!\n");
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replace_list (expr, copy_list (tail));
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break;
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default: break;
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}
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}
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#ifdef DEBUG
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printf ("*** expr after argument substitutions:\n");
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print_list (original_expr, stdout);
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putchar ('\n');
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#endif
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}
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