cpython/Parser/firstsets.c

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/***********************************************************
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Copyright (c) 2000, BeOpen.com.
Copyright (c) 1995-2000, Corporation for National Research Initiatives.
Copyright (c) 1990-1995, Stichting Mathematisch Centrum.
All rights reserved.
See the file "Misc/COPYRIGHT" for information on usage and
redistribution of this file, and for a DISCLAIMER OF ALL WARRANTIES.
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******************************************************************/
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/* Computation of FIRST stets */
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#include "pgenheaders.h"
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#include "grammar.h"
#include "token.h"
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extern int Py_DebugFlag;
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/* Forward */
static void calcfirstset(grammar *, dfa *);
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void
addfirstsets(grammar *g)
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{
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);
}
}
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static void
calcfirstset(grammar *g, dfa *d)
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{
int i, j;
state *s;
arc *a;
int nsyms;
int *sym;
int nbits;
static bitset dummy;
bitset result;
int type;
dfa *d1;
label *l0;
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if (Py_DebugFlag)
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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);
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sym = PyMem_NEW(int, 1);
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if (sym == NULL)
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Py_FatalError("no mem for new sym in calcfirstset");
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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 */
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PyMem_RESIZE(sym, int, nsyms + 1);
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if (sym == NULL)
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Py_FatalError(
"no mem to resize sym in calcfirstset");
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sym[nsyms++] = a->a_lbl;
type = l0[a->a_lbl].lb_type;
if (ISNONTERMINAL(type)) {
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d1 = PyGrammar_FindDFA(g, type);
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if (d1->d_first == dummy) {
fprintf(stderr,
"Left-recursion below '%s'\n",
d->d_name);
}
else {
if (d1->d_first == NULL)
calcfirstset(g, d1);
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mergebitset(result,
d1->d_first, nbits);
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}
}
else if (ISTERMINAL(type)) {
addbit(result, a->a_lbl);
}
}
}
d->d_first = result;
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if (Py_DebugFlag) {
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printf("FIRST set for '%s': {", d->d_name);
for (i = 0; i < nbits; i++) {
if (testbit(result, i))
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printf(" %s", PyGrammar_LabelRepr(&l0[i]));
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}
printf(" }\n");
}
}