www.pudn.com > bison.zip > derives.c

/* Match rules with nonterminals for bison, 
   Copyright (C) 1984, 1989 Free Software Foundation, Inc. 
 
This file is part of Bison, the GNU Compiler Compiler. 
 
Bison is free software; you can redistribute it and/or modify 
it under the terms of the GNU General Public License as published by 
the Free Software Foundation; either version 2, or (at your option) 
any later version. 
 
Bison is distributed in the hope that it will be useful, 
but WITHOUT ANY WARRANTY; without even the implied warranty of 
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the 
GNU General Public License for more details. 
 
You should have received a copy of the GNU General Public License 
along with Bison; see the file COPYING.  If not, write to 
the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.  */ 
 
 
/* set_derives finds, for each variable (nonterminal), which rules can derive it. 
   It sets up the value of derives so that 
   derives[i - ntokens] points to a vector of rule numbers, 
   terminated with -1.  */ 
 
#include  
#include "system.h" 
#include "new.h" 
#include "types.h" 
#include "gram.h" 
 
 
short **derives; 
 
void 
set_derives() 
{ 
  register int i; 
  register int lhs; 
  register shorts *p; 
  register short *q; 
  register shorts **dset; 
  register shorts *delts; 
 
  dset = NEW2(nvars, shorts *) - ntokens; 
  delts = NEW2(nrules + 1, shorts); 
 
  p = delts; 
  for (i = nrules; i > 0; i--) 
    { 
      lhs = rlhs[i]; 
      if (lhs >= 0) 
	{ 
	  p->next = dset[lhs]; 
	  p->value = i; 
	  dset[lhs] = p; 
	  p++; 
	} 
    } 
 
  derives = NEW2(nvars, short *) - ntokens; 
  q = NEW2(nvars + nrules, short); 
 
  for (i = ntokens; i < nsyms; i++) 
    { 
      derives[i] = q; 
      p = dset[i]; 
      while (p) 
	{ 
	  *q++ = p->value; 
	  p = p->next; 
	} 
      *q++ = -1; 
    } 
 
#ifdef	DEBUG 
  print_derives(); 
#endif 
 
  FREE(dset + ntokens); 
  FREE(delts); 
} 
 
void 
free_derives() 
{ 
  FREE(derives[ntokens]); 
  FREE(derives + ntokens); 
} 
 
 
 
#ifdef	DEBUG 
 
print_derives() 
{ 
  register int i; 
  register short *sp; 
 
  extern char **tags; 
 
  printf("\n\n\nDERIVES\n\n"); 
 
  for (i = ntokens; i < nsyms; i++) 
    { 
      printf("%s derives", tags[i]); 
      for (sp = derives[i]; *sp > 0; sp++) 
	{ 
	  printf("  %d", *sp); 
	} 
      putchar('\n'); 
    } 
 
  putchar('\n'); 
} 
 
#endif