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Remove the useless rules from the parser.
* src/gram.h, src/gram.c (rules_swap, rule_rhs_length): New.
(ritem_longest_rhs): Use the latter.
* src/gram.h (rule_t): `number' is a new member.
* src/reader.c (packgram): Set it.
* src/reduce.c (reduce_grammar_tables): Move the useless rules at
the end of `rules', and count them out of `nrules'.
(reduce_output, dump_grammar): Adjust.
* src/print.c (print_grammar): It is no longer needed to check for
the usefulness of a rule, as useless rules are beyond `nrules + 1'.
* tests/reduce.at (Reduced Automaton): New test.
Changes in version 1.49a:
* False `Token not used' report fixed.
On a grammar such as
/* Allocate input grammar variables for bison,
This file is part of Bison, the GNU Compiler Compiler.
int error_token_number;
/*------------------------.
| Dump RITEM for traces. |
`------------------------*/
size_t
ritem_longest_rhs (void)
{
int i;
return max;
}
typedef struct rule_s
{
short lhs;
short *rhs;
short prec;
extern int error_token_number;
/* Dump RITEM for traces. */
void ritem_print PARAMS ((FILE *out));
fprintf (out, "%snn", _("Grammar"));
fprintf (out, " %sn", _("Number, Line, Rule"));
for (i = 1; i < nrules + 1; i++)
fputs ("nn", out);
while (p)
{
bucket *ruleprec = p->ruleprec;
rules[ruleno].lhs = p->sym->number;
rules[ruleno].rhs = ritem + itemno;
rules[ruleno].line = p->line;
bitset_set (V1, rules[i].precsym);
}
static void
reduce_grammar_tables (void)
{
if (nuseless_productions > 0)
{
int pn;
for (pn = 1; pn < nrules + 1; pn++)
rules[pn].useful = bitset_test (P, pn);
}
}
{
int i;
fprintf (out, "%snn", _("Useless rules:"));
fputs ("nn", out);
}
}
fprintf (out, "nn");
fprintf (out, "Rulesn-----nn");
fprintf (out, "Num (Prec, Assoc, Useful, Ritem Range) Lhs -> Rhs (Ritem range) [Num]n");
{
int rhs_count = 0;
/* Find the last RHS index in ritems. */
}
fprintf (out, "nn");
fprintf (out, "Rules interpretedn-----------------nn");
{
fprintf (out, "%-5d %s :", i, symbols[rules[i].lhs]->tag);
for (r = rules[i].rhs; *r >= 0; r++)
## ------------------- ##
## Underivable Rules. ##
## ------------------- ##
This commit is contained in:
Akim Demaille
448
ChangeLog
448
ChangeLog
@@ -1,3 +1,451 @@
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2002-04-07 Akim Demaille <akim@epita.fr>
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Remove the useless rules from the parser.
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* src/gram.h, src/gram.c (rules_swap, rule_rhs_length): New.
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(ritem_longest_rhs): Use the latter.
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* src/gram.h (rule_t): `number' is a new member.
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* src/reader.c (packgram): Set it.
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* src/reduce.c (reduce_grammar_tables): Move the useless rules at
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the end of `rules', and count them out of `nrules'.
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(reduce_output, dump_grammar): Adjust.
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* src/print.c (print_grammar): It is no longer needed to check for
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the usefulness of a rule, as useless rules are beyond `nrules + 1'.
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* tests/reduce.at (Reduced Automaton): New test.
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diff -x *.po -ur -x testsuite bison-1.49a/NEWS bison/NEWS
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--- bison-1.49a/NEWS Sun Apr 7 17:36:56 2002
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+++ bison/NEWS Sun Apr 7 18:19:39 2002
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@@ -3,6 +3,10 @@
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Changes in version 1.49a:
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+* Useless rules are actually removed.
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+ Before, Bison reported the useless rules, but, although not used,
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+ included them in the parsers.
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+
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* False `Token not used' report fixed.
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On a grammar such as
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diff -x *.po -ur -x testsuite bison-1.49a/src/gram.c bison/src/gram.c
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--- bison-1.49a/src/gram.c Sun Apr 7 17:36:56 2002
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+++ bison/src/gram.c Sun Apr 7 18:19:39 2002
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@@ -1,5 +1,5 @@
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/* Allocate input grammar variables for bison,
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- Copyright 1984, 1986, 1989, 2001 Free Software Foundation, Inc.
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+ Copyright 1984, 1986, 1989, 2001, 2002 Free Software Foundation, Inc.
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This file is part of Bison, the GNU Compiler Compiler.
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@@ -51,6 +51,51 @@
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int error_token_number;
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+/*----------------------------------.
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+| Swap the rules number R1 and R2. |
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+`----------------------------------*/
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+
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+void
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+rules_swap (int r1, int r2)
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+{
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+ /* The easy part: swap the immediate contents of the structures. */
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+ {
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+ rule_t rule = rules[r1];
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+ rules[r1] = rules[r2];
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+ rules[r2] = rule;
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+ }
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+
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+ /* The first negative number in the RHS is the rule number. */
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+ {
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+ short *rhsp;
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+ for (rhsp = rules[r1].rhs; *rhsp >= 0; ++rhsp)
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+ /* Nothing. */;
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+ assert (*rhsp == -r2);
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+ *rhsp = -r1;
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+
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+ for (rhsp = rules[r2].rhs; *rhsp >= 0; ++rhsp)
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+ /* Nothing. */;
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+ assert (*rhsp == -r1);
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+ *rhsp = -r2;
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+ }
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+}
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+
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+
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+/*--------------------------------------.
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+| Return the number of symbols in RHS. |
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+`--------------------------------------*/
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+
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+int
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+rule_rhs_length (rule_t *rule)
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+{
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+ int res = 0;
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+ short *rhsp;
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+ for (rhsp = rule->rhs; *rhsp >= 0; ++rhsp)
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+ ++res;
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+ return res;
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+}
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+
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+
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/*------------------------.
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| Dump RITEM for traces. |
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`------------------------*/
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@@ -76,23 +121,15 @@
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size_t
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ritem_longest_rhs (void)
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{
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- int length;
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- int max;
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+ int max = 0;
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int i;
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- length = 0;
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- max = 0;
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- for (i = 0; i < nritems; ++i)
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- if (ritem[i] >= 0)
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- {
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- length++;
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- }
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- else
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- {
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- if (length > max)
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- max = length;
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- length = 0;
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- }
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+ for (i = 1; i < nrules + 1; ++i)
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+ {
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+ int length = rule_rhs_length (&rules[i]);
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+ if (length > max)
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+ max = length;
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+ }
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return max;
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}
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diff -x *.po -ur -x testsuite bison-1.49a/src/gram.h bison/src/gram.h
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--- bison-1.49a/src/gram.h Sun Apr 7 17:55:00 2002
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+++ bison/src/gram.h Sun Apr 7 18:19:39 2002
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@@ -124,6 +124,10 @@
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typedef struct rule_s
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{
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+ /* The number of the rule in the source. It is usually the index in
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+ RULES too, except if there are useless rules. */
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+ short number;
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+
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short lhs;
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short *rhs;
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short prec;
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@@ -166,6 +170,11 @@
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extern int error_token_number;
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+/* Swap two rules. */
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+void rules_swap PARAMS ((int r1, int r2));
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+
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+/* Report the length of the RHS. */
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+int rule_rhs_length PARAMS ((rule_t *rule));
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/* Dump RITEM for traces. */
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void ritem_print PARAMS ((FILE *out));
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diff -x *.po -ur -x testsuite bison-1.49a/src/print.c bison/src/print.c
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--- bison-1.49a/src/print.c Sun Apr 7 17:55:00 2002
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+++ bison/src/print.c Sun Apr 7 18:19:39 2002
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@@ -366,19 +366,17 @@
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fprintf (out, "%s\n\n", _("Grammar"));
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fprintf (out, " %s\n", _("Number, Line, Rule"));
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for (i = 1; i < nrules + 1; i++)
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- /* Don't print rules disabled in reduce_grammar_tables. */
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- if (rules[i].useful)
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- {
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- fprintf (out, _(" %3d %3d %s ->"),
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- i - 1, rules[i].line, escape (symbols[rules[i].lhs]->tag));
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- rule = rules[i].rhs;
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- if (*rule >= 0)
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- while (*rule >= 0)
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- fprintf (out, " %s", escape (symbols[*rule++]->tag));
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- else
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- fprintf (out, " /* %s */", _("empty"));
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- fputc ('\n', out);
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- }
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+ {
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+ fprintf (out, _(" %3d %3d %s ->"),
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+ i - 1, rules[i].line, escape (symbols[rules[i].lhs]->tag));
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+ rule = rules[i].rhs;
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+ if (*rule >= 0)
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+ while (*rule >= 0)
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+ fprintf (out, " %s", escape (symbols[*rule++]->tag));
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+ else
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+ fprintf (out, " /* %s */", _("empty"));
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+ fputc ('\n', out);
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+ }
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fputs ("\n\n", out);
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diff -x *.po -ur -x testsuite bison-1.49a/src/reader.c bison/src/reader.c
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--- bison-1.49a/src/reader.c Sun Apr 7 17:56:13 2002
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+++ bison/src/reader.c Sun Apr 7 18:19:39 2002
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@@ -1687,6 +1687,7 @@
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while (p)
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{
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bucket *ruleprec = p->ruleprec;
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+ rules[ruleno].number = ruleno;
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rules[ruleno].lhs = p->sym->number;
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rules[ruleno].rhs = ritem + itemno;
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rules[ruleno].line = p->line;
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diff -x *.po -ur -x testsuite bison-1.49a/src/reduce.c bison/src/reduce.c
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--- bison-1.49a/src/reduce.c Sun Apr 7 17:55:00 2002
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+++ bison/src/reduce.c Sun Apr 7 18:19:39 2002
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@@ -220,70 +220,59 @@
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bitset_set (V1, rules[i].precsym);
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}
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+
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+/*-------------------------------------------------------------------.
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+| Put the useless productions at the end of RULES, and adjust NRULES |
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+| accordingly. |
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+`-------------------------------------------------------------------*/
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+
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static void
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reduce_grammar_tables (void)
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{
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- /* This is turned off because we would need to change the numbers in
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- the case statements in the actions file.
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-
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- We don't disable it via CPP so that it is still checked with the
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- rest of the code, to avoid its becoming completely obsolete.
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-
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- FIXME: I think the comment above demonstrates this code must be
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- turned off for *semantic* parser, not in the general case. Try
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- to understand this better --akim. */
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-
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- if (0)
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- /* remove useless productions */
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- if (nuseless_productions > 0)
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- {
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- short np, pn, ni, pi;
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-
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- np = 0;
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- ni = 0;
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- for (pn = 1; pn < nrules + 1; pn++)
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- if (bitset_test (P, pn))
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- {
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- np++;
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- if (pn != np)
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- {
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- rules[np].lhs = rules[pn].lhs;
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- rules[np].line = rules[pn].line;
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- rules[np].prec = rules[pn].prec;
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- rules[np].assoc = rules[pn].assoc;
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- rules[np].rhs = rules[pn].rhs;
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- if (rules[np].rhs - ritem != ni)
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- {
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- pi = rules[np].rhs - ritem;
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- rules[np].rhs = ritem + ni;
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- while (ritem[pi] >= 0)
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- ritem[ni++] = ritem[pi++];
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- ritem[ni++] = -np;
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- }
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- }
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- else
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- {
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- while (ritem[ni++] >= 0)
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- /* Nothing. */;
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- }
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- }
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-
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- ritem[ni] = 0;
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- nrules -= nuseless_productions;
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- nitems = ni;
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- nritems = ni;
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-
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- /* Is it worth it to reduce the amount of memory for the
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- grammar? Probably not. */
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- }
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-
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- /* Disable useless productions. */
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+ /* Flag useless productions. */
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if (nuseless_productions > 0)
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{
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int pn;
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for (pn = 1; pn < nrules + 1; pn++)
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rules[pn].useful = bitset_test (P, pn);
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}
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+
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+ /* Map the nonterminals to their new index: useful first, useless
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+ afterwards. Kept for later report. */
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+ if (nuseless_productions > 0)
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+ {
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+ short *map = XCALLOC (short, nrules + 1) - 1;
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+ int useful = 1;
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+ int useless = nrules + 1 - nuseless_productions;
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+ int i;
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+ for (i = 1; i < nrules + 1; ++i)
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+ map[i] = rules[i].useful ? useful++ : useless++;
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+
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+ /* Shuffle elements of tables indexed by symbol number. */
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+ for (i = 1; i < nrules + 1; ++i)
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+ if (i != map[i])
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+ {
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+ int j = map[i];
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+ rules_swap (i, map[i]);
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+ map[i] = map[j];
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+ map[j] = j;
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+ }
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+
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+ free (map + 1);
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+ nrules -= nuseless_productions;
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+ }
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+
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+ /* Adjust NRITEMS and NITEMS. */
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+ {
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+ int r;
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+ int length;
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+ for (r = nrules + 1; r < nrules + 1 + nuseless_productions; ++r)
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+ {
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+ length = rule_rhs_length (&rules[r]);
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+ nritems -= length + 1;
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+ nitems -= length + 1;
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+ }
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+ }
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}
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@@ -378,16 +367,15 @@
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{
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int i;
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fprintf (out, "%s\n\n", _("Useless rules:"));
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- for (i = 1; i < nrules + 1; i++)
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- if (!rules[i].useful)
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- {
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- rule r;
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- fprintf (out, "#%-4d ", i - 1);
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- fprintf (out, "%s:", symbols[rules[i].lhs]->tag);
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- for (r = rules[i].rhs; *r >= 0; r++)
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- fprintf (out, " %s", symbols[*r]->tag);
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- fputs (";\n", out);
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- }
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+ for (i = nrules + 1; i < nuseless_productions + nrules + 1; i++)
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+ {
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+ rule r;
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+ fprintf (out, "#%-4d ", rules[i].number - 1);
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+ fprintf (out, "%s:", symbols[rules[i].lhs]->tag);
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+ for (r = rules[i].rhs; *r >= 0; r++)
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+ fprintf (out, " %s", symbols[*r]->tag);
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+ fputs (";\n", out);
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+ }
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fputs ("\n\n", out);
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}
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}
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@@ -411,7 +399,7 @@
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fprintf (out, "\n\n");
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fprintf (out, "Rules\n-----\n\n");
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fprintf (out, "Num (Prec, Assoc, Useful, Ritem Range) Lhs -> Rhs (Ritem range) [Num]\n");
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- for (i = 1; i < nrules + 1; i++)
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+ for (i = 1; i < nrules + nuseless_productions + 1; i++)
|
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{
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int rhs_count = 0;
|
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/* Find the last RHS index in ritems. */
|
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@@ -429,7 +417,7 @@
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}
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fprintf (out, "\n\n");
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fprintf (out, "Rules interpreted\n-----------------\n\n");
|
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- for (i = 1; i < nrules + 1; i++)
|
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+ for (i = 1; i < nrules + nuseless_productions + 1; i++)
|
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{
|
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fprintf (out, "%-5d %s :", i, symbols[rules[i].lhs]->tag);
|
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for (r = rules[i].rhs; *r >= 0; r++)
|
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diff -x *.po -ur -x testsuite bison-1.49a/tests/reduce.at bison/tests/reduce.at
|
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--- bison-1.49a/tests/reduce.at Sun Apr 7 17:36:56 2002
|
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+++ bison/tests/reduce.at Sun Apr 7 18:19:39 2002
|
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@@ -174,6 +174,89 @@
|
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|
||||
|
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## ------------------- ##
|
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+## Reduced Automaton. ##
|
||||
+## ------------------- ##
|
||||
+
|
||||
+# Check that the automaton is that as the for the grammar reduced by
|
||||
+# hand.
|
||||
+
|
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+AT_SETUP([Reduced Automaton])
|
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+
|
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+# The non reduced grammar.
|
||||
+# ------------------------
|
||||
+AT_DATA([[not-reduced.y]],
|
||||
+[[/* A useless token. */
|
||||
+%token useless_token
|
||||
+/* A useful one. */
|
||||
+%token useful
|
||||
+%verbose
|
||||
+%output="not-reduced.c"
|
||||
+
|
||||
+%%
|
||||
+
|
||||
+exp: useful { /* A useful action. */ }
|
||||
+ | non_productive { /* A non productive action. */ }
|
||||
+ ;
|
||||
+
|
||||
+not_reachable: useful { /* A not reachable action. */ }
|
||||
+ ;
|
||||
+
|
||||
+non_productive: non_productive useless_token
|
||||
+ { /* Another non productive action. */ }
|
||||
+ ;
|
||||
+]])
|
||||
+
|
||||
+AT_CHECK([[bison not-reduced.y]], 0, [],
|
||||
+[[not-reduced.y contains 2 useless nonterminals and 3 useless rules
|
||||
+]])
|
||||
+
|
||||
+AT_CHECK([[sed -n '/^Grammar/q;/^$/!p' not-reduced.output]], 0,
|
||||
+[[Useless nonterminals:
|
||||
+ not_reachable
|
||||
+ non_productive
|
||||
+Terminals which are not used:
|
||||
+ useless_token
|
||||
+Useless rules:
|
||||
+#2 exp: non_productive;
|
||||
+#3 not_reachable: useful;
|
||||
+#4 non_productive: non_productive useless_token;
|
||||
+]])
|
||||
+
|
||||
+# The reduced grammar.
|
||||
+# --------------------
|
||||
+AT_DATA([[reduced.y]],
|
||||
+[[/* A useless token. */
|
||||
+%token useless_token
|
||||
+/* A useful one. */
|
||||
+%token useful
|
||||
+%verbose
|
||||
+%output="reduced.c"
|
||||
+
|
||||
+%%
|
||||
+
|
||||
+exp: useful { /* A useful action. */ }
|
||||
+// | non_productive { /* A non productive action. */ } */
|
||||
+ ;
|
||||
+
|
||||
+//not_reachable: useful { /* A not reachable action. */ }
|
||||
+// ;
|
||||
+
|
||||
+//non_productive: non_productive useless_token
|
||||
+// { /* Another non productive action. */ }
|
||||
+// ;
|
||||
+]])
|
||||
+
|
||||
+AT_CHECK([[bison reduced.y]])
|
||||
+
|
||||
+# Comparing the parsers.
|
||||
+cp reduced.c expout
|
||||
+AT_CHECK([sed 's/not-reduced/reduced/g' not-reduced.c], 0, [expout])
|
||||
+
|
||||
+AT_CLEANUP
|
||||
+
|
||||
+
|
||||
+
|
||||
+## ------------------- ##
|
||||
## Underivable Rules. ##
|
||||
## ------------------- ##
|
||||
|
||||
2002-04-07 Akim Demaille <akim@epita.fr>
|
||||
|
||||
* src/reduce.c (inaccessable_symbols): Fix a buglet: because of a
|
||||
|
||||
Reference in New Issue
Block a user