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glr2.cc: add an example
Currently this example crashes on input such as "T (x) + y;". The same example with glr.c works properly. * examples/c++/glr/Makefile, examples/c++/glr/README.md, * examples/c++/glr/c++-types.test, examples/c++/glr/c++-types.yy, * examples/c++/glr/local.mk, examples/c++/local.mk: New. Based on examples/c/glr/c++-types.y.
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9 files changed

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‎data/skeletons/glr2.cc‎

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Original file line numberDiff line numberDiff line change
@@ -2092,7 +2092,7 @@ class glr_stack
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{
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state_set_index yynewStack = yystateStack.yysplitStack (yyk);
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YY_DEBUG_STREAM << "Splitting off stack " << yynewStack.get()
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<< " from " << yyk.get();
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<< " from " << yyk.get() << '\n';
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YYRESULTTAG yyflag =
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yyglrReduce (yynewStack, *yyconflicts,
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yyimmediate[*yyconflicts]);

‎examples/c++/calc++/local.mk‎

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@@ -18,14 +18,14 @@
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## Parser generation. ##
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## ------------------- ##
2020

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%D%/parser.stamp: $(dependencies)
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SUFFIXES += .yy .stamp
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.yy.stamp:
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$(AM_V_YACC)rm -f $@
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$(AM_V_at)touch $@.tmp
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$(AM_V_at)$(YACCCOMPILE) -o $*.cc $<
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$(AM_V_at)mv -f $@.tmp $@
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%D%/parser.stamp: $(dependencies)
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$(calcxx_sources_generated): %D%/parser.stamp
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@test -f $@ || rm -f %D%/parser.stamp
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@test -f $@ || $(MAKE) $(AM_MAKEFLAGS) %D%/parser.stamp

‎examples/c++/glr/Makefile‎

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@@ -0,0 +1,28 @@
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# This Makefile is designed to be simple and readable. It does not
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# aim at portability. It requires GNU Make.
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BASE = c++-types
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BISON = bison
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XSLTPROC = xsltproc
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all: $(BASE)
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%.c %.h %.xml %.gv: %.y
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$(BISON) $(BISONFLAGS) --defines --xml --graph=$*.gv -o $*.c $<
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$(BASE): $(BASE).o
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$(CC) $(CFLAGS) -o $@ $^
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run: $(BASE)
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@echo "Type C++ declarations or expressions. Quit with ctrl-d."
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./$<
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html: $(BASE).html
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%.html: %.xml
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$(XSLTPROC) $(XSLTPROCFLAGS) -o $@ $$($(BISON) --print-datadir)/xslt/xml2xhtml.xsl $<
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CLEANFILES = \
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$(BASE) *.o $(BASE).[ch] $(BASE).output $(BASE).xml $(BASE).html $(BASE).gv
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clean:
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rm -f $(CLEANFILES)

‎examples/c++/glr/README.md‎

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@@ -0,0 +1,24 @@
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# glr
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This example demonstrates the use of GLR parsers to handle (local)
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ambiguities in the C++ language. See the node "Merging GLR Parses" in
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Bison's documentation.
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<!---
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Local Variables:
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fill-column: 76
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ispell-dictionary: "american"
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End:
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Copyright (C) 2020 Free Software Foundation, Inc.
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This file is part of Bison, the GNU Compiler Compiler.
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Permission is granted to copy, distribute and/or modify this document
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under the terms of the GNU Free Documentation License, Version 1.3 or
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any later version published by the Free Software Foundation; with no
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Invariant Sections, with no Front-Cover Texts, and with no Back-Cover
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Texts. A copy of the license is included in the "GNU Free
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Documentation License" file as part of this distribution.
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--->

‎examples/c++/glr/c++-types.test‎

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@@ -0,0 +1,52 @@
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#! /bin/sh
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# Copyright (C) 2020 Free Software Foundation, Inc.
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#
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# This program is free software: you can redistribute it and/or modify
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# it under the terms of the GNU General Public License as published by
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# the Free Software Foundation, either version 3 of the License, or
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# (at your option) any later version.
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#
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# This program is distributed in the hope that it will be useful,
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# but WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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# GNU General Public License for more details.
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#
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# You should have received a copy of the GNU General Public License
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# along with this program. If not, see <http://www.gnu.org/licenses/>.
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cat >input <<EOF
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z + q;
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T x;
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T x = y;
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x = y;
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EOF
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run 0 "\
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1.0-4: +(z, q)
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3.0-2: <declare>(T, x)
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5.0-6: <init-declare>(T, x, y)
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7.0-4: =(x, y)"
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exit 77
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cat >input <<EOF
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T (x) + y;
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T (x);
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T (y) = z + q;
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T (y y) = z + q;
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z + q;
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EOF
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run 0 "\
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1.0-8: +(<cast>(x, T), y)
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3.0-4: <OR>(<declare>(T, x), <cast>(x, T))
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5.0-12: <OR>(<init-declare>(T, y, +(z, q)), =(<cast>(y, T), +(z, q)))
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7.0-14: <error>
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9.0-4: +(z, q)
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err: 7.5: syntax error, unexpected identifier, expecting '=' or '+' or ')'"

‎examples/c++/glr/c++-types.yy‎

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/* Simplified -*- C++ -*- Type and Expression Grammar. */
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%glr-parser
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%skeleton "glr2.cc"
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%header
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%locations
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%debug
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/* Nice error messages with details. */
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%define parse.error detailed
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%code requires
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{
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union Node {
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struct {
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int isNterm;
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int parents;
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} nodeInfo;
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struct {
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int isNterm; /* 1 */
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int parents;
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char const *form;
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union Node *children[3];
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} nterm;
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struct {
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int isNterm; /* 0 */
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int parents;
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char *text;
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} term;
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};
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typedef union Node Node;
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}
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%define api.value.type {Node *}
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%code
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{
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#include <cassert>
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#include <cctype>
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#include <cstdio>
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#include <cstdlib>
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#include <cstring>
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static Node *new_nterm (char const *form, Node *child0 = nullptr, Node *child1 = nullptr, Node *child2 = nullptr);
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static Node *new_term (char *);
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static void free_node (Node *);
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static std::ostream& operator<< (std::ostream& o, const Node &node);
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static YYSTYPE stmtMerge (YYSTYPE x0, YYSTYPE x1);
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static int yylex (YYSTYPE *lvalp, YYLTYPE *llocp);
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}
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%expect-rr 1
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%token
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TYPENAME "typename"
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ID "identifier"
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%right '='
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%left '+'
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%destructor { free_node ($$); } stmt expr decl declarator TYPENAME ID
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%%
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prog : %empty
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| prog stmt { std::cout << @2 << ": " << *$2 << '\n'; free_node ($2); }
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;
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stmt : expr ';' %merge <stmtMerge> { $$ = $1; }
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| decl %merge <stmtMerge>
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| error ';' { $$ = new_nterm ("<error>"); }
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| '@' { $$ = $1; YYACCEPT; }
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;
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expr : ID
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| TYPENAME '(' expr ')'
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{ $$ = new_nterm ("<cast>", $3, $1); }
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| expr '+' expr { $$ = new_nterm ("+", $1, $3); }
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| expr '=' expr { $$ = new_nterm ("=", $1, $3); }
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;
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decl : TYPENAME declarator ';'
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{ $$ = new_nterm ("<declare>", $1, $2); }
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| TYPENAME declarator '=' expr ';'
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{ $$ = new_nterm ("<init-declare>", $1,
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$2, $4); }
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;
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declarator
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: ID
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| '(' declarator ')' { $$ = $2; }
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;
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%%
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int
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main (int argc, char **argv)
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{
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// Enable parse traces on option -p.
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if (1 < argc && strcmp (argv[1], "-p") == 0)
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yydebug = 1;
104+
yy::parser parser;
105+
return !!parser.parse ();
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}
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/* A C error reporting function. */
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void yy::parser::error (const location_type& l, const std::string& m)
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{
112+
std::cerr << l << ": " << m << '\n';
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}
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int yylex (YYSTYPE *lvalp, YYLTYPE *llocp)
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{
117+
static int lineNum = 1;
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static int colNum = 0;
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while (1)
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{
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int c;
123+
assert (!feof (stdin));
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c = getchar ();
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switch (c)
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{
127+
case EOF:
128+
return 0;
129+
case '\t':
130+
colNum = (colNum + 7) & ~7;
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break;
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case ' ': case '\f':
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colNum += 1;
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break;
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case '\n':
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lineNum += 1;
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colNum = 0;
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break;
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default:
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{
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int tok;
142+
llocp->begin.line = llocp->end.line = lineNum;
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llocp->begin.column = colNum;
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if (isalpha (c))
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{
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char buffer[256];
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unsigned i = 0;
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do
150+
{
151+
buffer[i++] = static_cast<char> (c);
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colNum += 1;
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assert (i != sizeof buffer - 1);
154+
c = getchar ();
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}
156+
while (isalnum (c) || c == '_');
157+
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ungetc (c, stdin);
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buffer[i++] = 0;
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tok
161+
= isupper (static_cast <unsigned char> (buffer[0]))
162+
? yy::parser::token::TYPENAME
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: yy::parser::token::ID;
164+
*lvalp = new_term (strcpy (static_cast<char*> (malloc (i)), buffer));
165+
}
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else
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{
168+
colNum += 1;
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tok = c;
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*lvalp = NULL;
171+
}
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llocp->end.column = colNum-1;
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return tok;
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}
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}
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}
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}
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static Node *
180+
new_nterm (char const *form, Node *child0, Node *child1, Node *child2)
181+
{
182+
Node *res = new Node;
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res->nterm.isNterm = 1;
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res->nterm.parents = 0;
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res->nterm.form = form;
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res->nterm.children[0] = child0;
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if (child0)
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child0->nodeInfo.parents += 1;
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res->nterm.children[1] = child1;
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if (child1)
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child1->nodeInfo.parents += 1;
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res->nterm.children[2] = child2;
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if (child2)
194+
child2->nodeInfo.parents += 1;
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return res;
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}
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static Node *
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new_term (char *text)
200+
{
201+
Node *res = new Node;
202+
res->term.isNterm = 0;
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res->term.parents = 0;
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res->term.text = text;
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return res;
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}
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static void
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free_node (Node *node)
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{
211+
if (!node)
212+
return;
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node->nodeInfo.parents -= 1;
214+
/* Free only if 0 (last parent) or -1 (no parents). */
215+
if (node->nodeInfo.parents > 0)
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return;
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if (node->nodeInfo.isNterm == 1)
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{
219+
free_node (node->nterm.children[0]);
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free_node (node->nterm.children[1]);
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free_node (node->nterm.children[2]);
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}
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else
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free (node->term.text);
225+
delete node;
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}
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static std::ostream&
229+
operator<< (std::ostream& o, const Node &node)
230+
{
231+
if (node.nodeInfo.isNterm == 1)
232+
{
233+
o << node.nterm.form;
234+
if (node.nterm.children[0])
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{
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o << '(' << *node.nterm.children[0];
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if (node.nterm.children[1])
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o << ", " << *node.nterm.children[1];
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if (node.nterm.children[2])
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o << ", " << *node.nterm.children[2];
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o << ")";
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}
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}
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else
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o << node.term.text;
246+
return o;
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}
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static YYSTYPE
251+
stmtMerge (YYSTYPE x0, YYSTYPE x1)
252+
{
253+
return new_nterm ("<OR>", x0, x1);
254+
}
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