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This patch was inspired by work by Michiel De Wilde. But he used Boost variants which (i) requires Boost on the user side, (ii) is slow, and (iii) has useless overhead (the parser knows the type of the semantic value there is no reason to duplicate this information as Boost.Variants do). This implementation reserves a buffer large enough to store the largest objects. yy::variant implements this buffer. It was implemented with Quentin Hocquet. * src/output.c (type_names_output): New. (output_skeleton): Invoke it. * data/c++.m4 (b4_variant_if): New. (b4_symbol_value): If needed, provide a definition for variants. * data/lalr1.cc (b4_symbol_value, b4_symbol_action_) (b4_symbol_variant, _b4_char_sizeof_counter, _b4_char_sizeof_dummy) (b4_char_sizeof, yy::variant): New. (parser::parse): If variants are requested, define parser::union_type, parser::variant, change the definition of semantic_type, construct $$ before running the user action instead of performing a default $$ = $1. * examples/variant.yy: New. Based on an example by Michiel De Wilde.
-*- outline -*- This directory contains Bison skeletons: the general shapes of the different parser kinds, that are specialized for specific grammars by the bison program. Currently, there are only three supported skeletons: - 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. It is still very experimental, and not yet supported. Please, subscribe to bison-patches@gnu.org. - glr.c A Generalized LR C parser based on Bison's LALR(1) tables. 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. ----- Copyright (C) 2002 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/>.