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ca2a6d1587
These changes allow users to prefix an action with %? to indicate that it
is a semantic predicate---an expression that is evaluated immediately (not
deferred, even in GLR nondeterministic mode) and causes a syntax error if
false. In GLR parsers, this has the effect of killing one of a set of
split-off parses, just as would an ordinary syntax error.
Changelog:
* NEWS: Describe new semantic-predicate feature.
* data/c.m4 (b4_predicate_case): New definition.
* data/java.m4 (b4_predicate_case): New definition.
* data/glr.c (yyimmediate): Add definition.
(yydoAction): Remove comment, now obsolete.
Do YY_REDUCE_PRINT here.
(yyglrReduce): Alter comment to indicate that semantic values
need not be deferred.
Remove YY_REDUCE_PRINT from here; done in yydoAction.
(yyprocessOneStack): Pass immediate flag.
Delete stacks rejected by predicates in newly split-off parsers.
Change handling of yyerr so that only current stack gets deleted
when semantic predicate fails.
(yyfillin): Don't crash if a semantic value is unresolved (as may
happen in predicate rules).
Copy lr state as well in debugging mode.
Update comment on setting of yysval to include yyloc as well.
(yy_reduce_print): Add yynormal argument. Perform fillin properly.
Report unresolved RHS values.
(yyimmediate): New table.
* src/gram.h (struct rule): Add is_predicate field.
* src/output.c (user_actions_output): Use b4_predicate_case for
predicates.
(prepare_symbols): Output yyimmediate.
* src/scan-gram.l: Add %? token, SC_PREDICATE state.
* src/scan-code.l (code_props_rule_action_init): Add is_predicate
argument.
* src/scan-code.h (struct code_props): Add is_predicate field.
(code_props_rule_action_init): New interface.
* src/parse-gram.y (%?{...}): New token.
(rhs): Add %?{...} rule.
* src/parse-gram.c: Regenerate.
* src/parse-gram.h: Regenerate.
* src/reader.c (grammar_current_rule_action_append): Add
immediate argument.
(grammar_midrule_action): Use new interface for
code_props_rule_action_init.
(grammar_current_rule_action_append): Ditto.
(packgram): Transfer is_predicate value.
* src/reader.h (grammar_current_rule_action_append): New interface.
* doc/bison.texinfo: Document semantic predicates (%?).
* data/glr.c (yylhsNonterm, yyisDefaultedState,yyDefaultAction)
(yygetLRActions,yynewGLRStackItem,yyaddDeferredAction,yyinitStateSet)
(yyinitGLRStack,yyexpandGLRStack,yyupdateSplit,yymarkStackDeleted)
(yyundeleteLastStack,yyglrShift,yyglrShiftDefer,yydoAction,yyglrReduce)
(yyidenticalOptions,yymergeOptionSets,yyresolveStates,yyresolveAction)
(yyresolveLocations,yyresolveValue,yyreducePrint): Update parameter
names in comments and mention all parameters.
(struct yyGLRState): Fix description of yyposn field.
(yyresolveLocations): Correct comment so as not to imply action when
yyn1==0.
-*- outline -*- This directory contains data needed by Bison. * Skeletons Bison skeletons: the general shapes of the different parser kinds, that are specialized for specific grammars by the bison program. Currently, the supported skeletons are: - yacc.c It used to be named bison.simple: it corresponds to C Yacc compatible LALR(1) parsers. - lalr1.cc Produces a C++ parser class. - lalr1.java Produces a Java parser class. - glr.c A Generalized LR C parser based on Bison's LALR(1) tables. - glr.cc A Generalized LR C++ parser. Actually a C++ wrapper around glr.c. These skeletons are the only ones supported by the Bison team. Because the interface between skeletons and the bison program is not finished, *we are not bound to it*. In particular, Bison is not mature enough for us to consider that ``foreign skeletons'' are supported. * m4sugar This directory contains M4sugar, sort of an extended library for M4, which is used by Bison to instantiate the skeletons. * xslt This directory contains XSLT programs that transform Bison's XML output into various formats. - bison.xsl A library of routines used by the other XSLT programs. - xml2dot.xsl Conversion into GraphViz's dot format. - xml2text.xsl Conversion into text. - xml2xhtml.xsl Conversion into XHTML. ----- Copyright (C) 2002, 2008, 2009, 2010 Free Software Foundation, Inc. This file is part of GNU Bison. This program 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 3 of the License, or (at your option) any later version. This program 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 this program. If not, see <http://www.gnu.org/licenses/>.