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 "alloc.h"
  29 #include "types.h"
  30 #include "gram.h"
  31
  32 void set_derives PARAMS((void));
  33 void free_derives PARAMS((void));
  34
  35 short **derives;
  36
  37 void
  38 set_derives (void)
  39 {
  40   register int i;
  41   register int lhs;
  42   register shorts *p;
  43   register short *q;
  44   register shorts **dset;
  45   register shorts *delts;
  46
  47   dset = NEW2(nvars, shorts *) - ntokens;
  48   delts = NEW2(nrules + 1, shorts);
  49
  50   p = delts;
  51   for (i = nrules; i > 0; i--)
  52     {
  53       lhs = rlhs[i];
  54       if (lhs >= 0)
  55         {
  56           p->next = dset[lhs];
  57           p->value = i;
  58           dset[lhs] = p;
  59           p++;
  60         }
  61     }
  62
  63   derives = NEW2(nvars, short *) - ntokens;
  64   q = NEW2(nvars + nrules, short);
  65
  66   for (i = ntokens; i < nsyms; i++)
  67     {
  68       derives[i] = q;
  69       p = dset[i];
  70       while (p)
  71         {
  72           *q++ = p->value;
  73           p = p->next;
  74         }
  75       *q++ = -1;
  76     }
  77
  78 #ifdef  DEBUG
  79   print_derives();
  80 #endif
  81
  82   FREE(dset + ntokens);
  83   FREE(delts);
  84 }
  85
  86 void
  87 free_derives (void)
  88 {
  89   FREE(derives[ntokens]);
  90   FREE(derives + ntokens);
  91 }
  92
  93
  94
  95 #ifdef  DEBUG
  96
  97 void
  98 print_derives (void)
  99 {
 100   register int i;
 101   register short *sp;
 102
 103   extern char **tags;
 104
 105   printf(_("\n\n\nDERIVES\n\n"));
 106
 107   for (i = ntokens; i < nsyms; i++)
 108     {
 109       printf(_("%s derives"), tags[i]);
 110       for (sp = derives[i]; *sp > 0; sp++)
 111         {
 112           printf("  %d", *sp);
 113         }
 114       putchar('\n');
 115     }
 116
 117   putchar('\n');
 118 }
 119
 120 #endif