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Guido van Rossum 1990-10-14 12:07:46 +00:00
parent c636014c43
commit 85a5fbbdfe
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109
Parser/firstsets.c Normal file
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/* Computation of FIRST stets */
#include <stdio.h>
#include "PROTO.h"
#include "malloc.h"
#include "grammar.h"
#include "token.h"
extern int debugging;
static void
calcfirstset(g, d)
grammar *g;
dfa *d;
{
int i, j;
state *s;
arc *a;
int nsyms;
int *sym;
int nbits;
static bitset dummy;
bitset result;
int type;
dfa *d1;
label *l0;
if (debugging)
printf("Calculate FIRST set for '%s'\n", d->d_name);
if (dummy == NULL)
dummy = newbitset(1);
if (d->d_first == dummy) {
fprintf(stderr, "Left-recursion for '%s'\n", d->d_name);
return;
}
if (d->d_first != NULL) {
fprintf(stderr, "Re-calculating FIRST set for '%s' ???\n",
d->d_name);
}
d->d_first = dummy;
l0 = g->g_ll.ll_label;
nbits = g->g_ll.ll_nlabels;
result = newbitset(nbits);
sym = NEW(int, 1);
if (sym == NULL)
fatal("no mem for new sym in calcfirstset");
nsyms = 1;
sym[0] = findlabel(&g->g_ll, d->d_type, (char *)NULL);
s = &d->d_state[d->d_initial];
for (i = 0; i < s->s_narcs; i++) {
a = &s->s_arc[i];
for (j = 0; j < nsyms; j++) {
if (sym[j] == a->a_lbl)
break;
}
if (j >= nsyms) { /* New label */
RESIZE(sym, int, nsyms + 1);
if (sym == NULL)
fatal("no mem to resize sym in calcfirstset");
sym[nsyms++] = a->a_lbl;
type = l0[a->a_lbl].lb_type;
if (ISNONTERMINAL(type)) {
d1 = finddfa(g, type);
if (d1->d_first == dummy) {
fprintf(stderr,
"Left-recursion below '%s'\n",
d->d_name);
}
else {
if (d1->d_first == NULL)
calcfirstset(g, d1);
mergebitset(result, d1->d_first, nbits);
}
}
else if (ISTERMINAL(type)) {
addbit(result, a->a_lbl);
}
}
}
d->d_first = result;
if (debugging) {
printf("FIRST set for '%s': {", d->d_name);
for (i = 0; i < nbits; i++) {
if (testbit(result, i))
printf(" %s", labelrepr(&l0[i]));
}
printf(" }\n");
}
}
void
addfirstsets(g)
grammar *g;
{
int i;
dfa *d;
printf("Adding FIRST sets ...\n");
for (i = 0; i < g->g_ndfas; i++) {
d = &g->g_dfa[i];
if (d->d_first == NULL)
calcfirstset(g, d);
}
}