text: /***********************************************************
  Copyright 1991 by Stichting Mathematisch Centrum, Amsterdam, The
  Netherlands.
  
                          All Rights Reserved
  
  Permission to use, copy, modify, and distribute this software and its
  documentation for any purpose and without fee is hereby granted,
  provided that the above copyright notice appear in all copies and that
  both that copyright notice and this permission notice appear in
  supporting documentation, and that the names of Stichting Mathematisch
  Centrum or CWI not be used in advertising or publicity pertaining to
  distribution of the software without specific, written prior permission.
  
  STICHTING MATHEMATISCH CENTRUM DISCLAIMS ALL WARRANTIES WITH REGARD TO
  THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND
  FITNESS, IN NO EVENT SHALL STICHTING MATHEMATISCH CENTRUM BE LIABLE
  FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
  WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
  ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT
  OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
  
  ******************************************************************/
  
  /* Computation of FIRST stets */
  
  #include "pgenheaders.h"
  #include "grammar.h"
  #include "token.h"
  
  extern int debugging;
  
  /* Forward */
  static void calcfirstset PROTO((grammar *, dfa *));
  
  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);
         }
  }
  
  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");
         }
  }
  