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Akim Demaille
2002-09-27 14:50:35 +00:00
parent c0cac722f7
commit a75649b395
1 changed files with 0 additions and 126 deletions
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src/injections.c
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/* Grammar reduction for Bison.
Copyright (C) 2002 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, Inc., 59 Temple Place - Suite 330,
Boston, MA 02111-1307, USA. */
/* Reduce the grammar: Look for injections. Akim Demaille. */
#include "system.h"
#include "quotearg.h"
#include "bitsetv.h"
#include "bitsetv-print.h"
#include "complain.h"
#include "gram.h"
#include "getargs.h"
#include "derives.h"
#include "injections.h"
/* Set of all nonterminals which are not useless. */
static bitsetv injects;
#define INJECTS(Var) injects[(Var) - ntokens]
/*-----------------------------------------------------------.
| Free the global sets used to compute the reduced grammar. |
`-----------------------------------------------------------*/
void
injections_new (void)
{
if (!injects)
injects = bitsetv_create (nvars, nvars, BITSET_FIXED);
else
bitsetv_zero (injects);
}
void
injections_free (void)
{
bitsetv_free (injects);
injects = NULL;
}
/*------------------------------.
| Dump the list of injections. |
`------------------------------*/
static void
injections_print (const char *title)
{
int i, j;
fprintf (stderr, "%s\n", title);
for (i = ntokens; i < nsyms; i++)
if (bitset_count (INJECTS (i)))
{
fprintf (stderr, "\t%s injects\n",
quotearg_style (escape_quoting_style, symbols[i]->tag));
for (j = 0; j < nvars; j++)
if (bitset_test (INJECTS (i), j))
fprintf (stderr, "\t\t%s\n",
quotearg_style (escape_quoting_style,
symbols[j + ntokens]->tag));
}
fprintf (stderr, "\n\n");
}
/*-----------------------------------------------------------------.
| Set INJECTS[i, j] if the nonterminal j derives the nonterminal j |
| (typically, `i -> j' is a rule, plus transitive closure). |
`-----------------------------------------------------------------*/
static void
injections_compute (void)
{
int i, j;
injections_new ();
for (i = ntokens; i < nsyms; i++)
for (j = 0; derives[i][j] >= 0; ++j)
{
int symbol = rules[derives[i][j]].rhs[0];
if (ISVAR (symbol) && rules[derives[i][j]].rhs[1] < 0)
bitset_set (INJECTS (i), symbol - ntokens);
}
if (trace_flag & trace_sets)
injections_print ("syntactic direct injections");
bitsetv_transitive_closure (injects);
if (trace_flag & trace_sets)
injections_print ("syntactic injections");
}
/*--------------------------------------------------------------.
| Look for infinitely ambiguous grammars: they contain cycles. |
`--------------------------------------------------------------*/
void
injections_check_cycles (void)
{
int i;
injections_compute ();
for (i = ntokens; i < nsyms; i++)
if (bitset_test (INJECTS (i), i - ntokens))
complain (_("infinitely ambiguous grammar: %s derives itself"),
symbols[i]->tag);
}