1991-02-19 12:39:46 +00:00
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/***********************************************************
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1992-04-05 14:26:55 +00:00
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Copyright 1991, 1992 by Stichting Mathematisch Centrum, Amsterdam, The
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1991-02-19 12:39:46 +00:00
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Netherlands.
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All Rights Reserved
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Permission to use, copy, modify, and distribute this software and its
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documentation for any purpose and without fee is hereby granted,
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provided that the above copyright notice appear in all copies and that
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both that copyright notice and this permission notice appear in
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supporting documentation, and that the names of Stichting Mathematisch
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Centrum or CWI not be used in advertising or publicity pertaining to
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distribution of the software without specific, written prior permission.
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STICHTING MATHEMATISCH CENTRUM DISCLAIMS ALL WARRANTIES WITH REGARD TO
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THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND
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FITNESS, IN NO EVENT SHALL STICHTING MATHEMATISCH CENTRUM BE LIABLE
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FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
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WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
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ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT
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OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
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******************************************************************/
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1990-10-14 12:07:46 +00:00
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/* Computation of FIRST stets */
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1990-12-20 15:06:42 +00:00
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#include "pgenheaders.h"
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1990-10-14 12:07:46 +00:00
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#include "grammar.h"
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#include "token.h"
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extern int debugging;
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1990-12-20 15:06:42 +00:00
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/* Forward */
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static void calcfirstset PROTO((grammar *, dfa *));
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void
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addfirstsets(g)
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grammar *g;
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{
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int i;
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dfa *d;
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printf("Adding FIRST sets ...\n");
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for (i = 0; i < g->g_ndfas; i++) {
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d = &g->g_dfa[i];
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if (d->d_first == NULL)
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calcfirstset(g, d);
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}
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}
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1990-10-14 12:07:46 +00:00
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static void
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calcfirstset(g, d)
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grammar *g;
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dfa *d;
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{
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int i, j;
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state *s;
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arc *a;
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int nsyms;
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int *sym;
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int nbits;
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static bitset dummy;
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bitset result;
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int type;
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dfa *d1;
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label *l0;
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if (debugging)
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printf("Calculate FIRST set for '%s'\n", d->d_name);
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if (dummy == NULL)
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dummy = newbitset(1);
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if (d->d_first == dummy) {
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fprintf(stderr, "Left-recursion for '%s'\n", d->d_name);
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return;
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}
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if (d->d_first != NULL) {
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fprintf(stderr, "Re-calculating FIRST set for '%s' ???\n",
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d->d_name);
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}
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d->d_first = dummy;
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l0 = g->g_ll.ll_label;
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nbits = g->g_ll.ll_nlabels;
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result = newbitset(nbits);
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sym = NEW(int, 1);
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if (sym == NULL)
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fatal("no mem for new sym in calcfirstset");
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nsyms = 1;
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sym[0] = findlabel(&g->g_ll, d->d_type, (char *)NULL);
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s = &d->d_state[d->d_initial];
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for (i = 0; i < s->s_narcs; i++) {
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a = &s->s_arc[i];
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for (j = 0; j < nsyms; j++) {
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if (sym[j] == a->a_lbl)
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break;
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}
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if (j >= nsyms) { /* New label */
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RESIZE(sym, int, nsyms + 1);
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if (sym == NULL)
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fatal("no mem to resize sym in calcfirstset");
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sym[nsyms++] = a->a_lbl;
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type = l0[a->a_lbl].lb_type;
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if (ISNONTERMINAL(type)) {
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d1 = finddfa(g, type);
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if (d1->d_first == dummy) {
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fprintf(stderr,
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"Left-recursion below '%s'\n",
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d->d_name);
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}
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else {
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if (d1->d_first == NULL)
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calcfirstset(g, d1);
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mergebitset(result, d1->d_first, nbits);
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}
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}
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else if (ISTERMINAL(type)) {
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addbit(result, a->a_lbl);
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}
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}
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}
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d->d_first = result;
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if (debugging) {
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printf("FIRST set for '%s': {", d->d_name);
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for (i = 0; i < nbits; i++) {
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if (testbit(result, i))
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printf(" %s", labelrepr(&l0[i]));
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}
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printf(" }\n");
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}
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}
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