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, Inc., 59 Temple Place - Suite 330,
  19 Boston, MA 02111-1307, USA.  */
  20
  21
  22 /* set_derives finds, for each variable (nonterminal), which rules can derive it.
  23    It sets up the value of derives so that
  24    derives[i - ntokens] points to a vector of rule numbers,
  25    terminated with -1.  */
  26
  27 #include <stdio.h>
  28 #include "system.h"
  29 #include "alloc.h"
  30 #include "types.h"
  31 #include "gram.h"
  32
  33 void set_derives PARAMS((void));
  34 void free_derives PARAMS((void));
  35
  36 short **derives;
  37
  38 void
  39 set_derives (void)
  40 {
  41   register int i;
  42   register int lhs;
  43   register shorts *p;
  44   register short *q;
  45   register shorts **dset;
  46   register shorts *delts;
  47
  48   dset = NEW2(nvars, shorts *) - ntokens;
  49   delts = NEW2(nrules + 1, shorts);
  50
  51   p = delts;
  52   for (i = nrules; i > 0; i--)
  53     {
  54       lhs = rlhs[i];
  55       if (lhs >= 0)
  56         {
  57           p->next = dset[lhs];
  58           p->value = i;
  59           dset[lhs] = p;
  60           p++;
  61         }
  62     }
  63
  64   derives = NEW2(nvars, short *) - ntokens;
  65   q = NEW2(nvars + nrules, short);
  66
  67   for (i = ntokens; i < nsyms; i++)
  68     {
  69       derives[i] = q;
  70       p = dset[i];
  71       while (p)
  72         {
  73           *q++ = p->value;
  74           p = p->next;
  75         }
  76       *q++ = -1;
  77     }
  78
  79 #ifdef  DEBUG
  80   print_derives();
  81 #endif
  82
  83   FREE(dset + ntokens);
  84   FREE(delts);
  85 }
  86
  87 void
  88 free_derives (void)
  89 {
  90   FREE(derives[ntokens]);
  91   FREE(derives + ntokens);
  92 }
  93
  94
  95
  96 #ifdef  DEBUG
  97
  98 void
  99 print_derives (void)
 100 {
 101   register int i;
 102   register short *sp;
 103
 104   extern char **tags;
 105
 106   printf(_("\n\n\nDERIVES\n\n"));
 107
 108   for (i = ntokens; i < nsyms; i++)
 109     {
 110       printf(_("%s derives"), tags[i]);
 111       for (sp = derives[i]; *sp > 0; sp++)
 112         {
 113           printf("  %d", *sp);
 114         }
 115       putchar('\n');
 116     }
 117
 118   putchar('\n');
 119 }
 120
 121 #endif