src/derives.c

   1 /* Match rules with nonterminals for bison,
   2    Copyright (C) 1984, 1989 Free Software Foundation, Inc.
   3
   4 This file is part of Bison, the GNU Compiler Compiler.
   5
   6 Bison is free software; you can redistribute it and/or modify
   7 it under the terms of the GNU General Public License as published by
   8 the Free Software Foundation; either version 2, or (at your option)
   9 any later version.
  10
  11 Bison is distributed in the hope that it will be useful,
  12 but WITHOUT ANY WARRANTY; without even the implied warranty of
  13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14 GNU General Public License for more details.
  15
  16 You should have received a copy of the GNU General Public License
  17 along with Bison; see the file COPYING.  If not, write to
  18 the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.  */
  19
  20
  21 /* set_derives finds, for each variable (nonterminal), which rules can derive it.
  22    It sets up the value of derives so that
  23    derives[i - ntokens] points to a vector of rule numbers,
  24    terminated with -1.  */
  25
  26 #include <stdio.h>
  27 #include "system.h"
  28 #include "new.h"
  29 #include "types.h"
  30 #include "gram.h"
  31
  32
  33 short **derives;
  34
  35 void
  36 set_derives()
  37 {
  38   register int i;
  39   register int lhs;
  40   register shorts *p;
  41   register short *q;
  42   register shorts **dset;
  43   register shorts *delts;
  44
  45   dset = NEW2(nvars, shorts *) - ntokens;
  46   delts = NEW2(nrules + 1, shorts);
  47
  48   p = delts;
  49   for (i = nrules; i > 0; i--)
  50     {
  51       lhs = rlhs[i];
  52       if (lhs >= 0)
  53         {
  54           p->next = dset[lhs];
  55           p->value = i;
  56           dset[lhs] = p;
  57           p++;
  58         }
  59     }
  60
  61   derives = NEW2(nvars, short *) - ntokens;
  62   q = NEW2(nvars + nrules, short);
  63
  64   for (i = ntokens; i < nsyms; i++)
  65     {
  66       derives[i] = q;
  67       p = dset[i];
  68       while (p)
  69         {
  70           *q++ = p->value;
  71           p = p->next;
  72         }
  73       *q++ = -1;
  74     }
  75
  76 #ifdef  DEBUG
  77   print_derives();
  78 #endif
  79
  80   FREE(dset + ntokens);
  81   FREE(delts);
  82 }
  83
  84 void
  85 free_derives()
  86 {
  87   FREE(derives[ntokens]);
  88   FREE(derives + ntokens);
  89 }
  90
  91
  92
  93 #ifdef  DEBUG
  94
  95 print_derives()
  96 {
  97   register int i;
  98   register short *sp;
  99
 100   extern char **tags;
 101
 102   printf("\n\n\nDERIVES\n\n");
 103
 104   for (i = ntokens; i < nsyms; i++)
 105     {
 106       printf("%s derives", tags[i]);
 107       for (sp = derives[i]; *sp > 0; sp++)
 108         {
 109           printf("  %d", *sp);
 110         }
 111       putchar('\n');
 112     }
 113
 114   putchar('\n');
 115 }
 116
 117 #endif
 118