Future/bison
1
0
Fork 0
mirror of https://git.savannah.gnu.org/git/bison.git synced 2026-03-09 04:13:03 +00:00
Code Issues Packages Projects Releases Wiki Activity

examples: add a simple Flex+Bison example in C

Browse Source 
Suggested by Askar Safin.
http://lists.gnu.org/archive/html/bug-bison/2018-12/msg00003.html

* examples/c/lexcalc/Makefile, examples/c/lexcalc/README.md,
* examples/c/lexcalc/lexcalc.test, examples/c/lexcalc/local.mk,
* examples/c/lexcalc/parse.y, examples/c/lexcalc/scan.l:
New.
This commit is contained in:
Akim Demaille
2018-12-09 14:19:00 +01:00
parent 4cbdcaa572
commit d657da9fb4
10 changed files with 270 additions and 6 deletions
Download Patch File Download Diff File Expand all files Collapse all files

3
NEWS
View File

@@ -142,7 +142,8 @@ GNU Bison NEWS
README and a Makefile. Not only can they be used to toy with Bison, they README and a Makefile. Not only can they be used to toy with Bison, they
can also be starting points for your own grammars. can also be starting points for your own grammars.
There is now a Java example. There is now a Java example, and a simple example in C based on Flex and
Bison (examples/c/lexcalc/).
** Changes ** Changes

11
examples/c++/calc++/README.md
View File

@@ -1,6 +1,10 @@
This directory contains calc++, a simple Bison grammar file in C++. # calc++ - A Flex+Bison calculator
Please, read the corresponding chapter in the documentation: "A Complete C++ This directory contains calc++, a Bison grammar file in C++. If you never
saw the traditional implementation in C, please first read
examples/c/lexcalc, which can be seen as a C precursor of this example.
Read the corresponding chapter in the documentation: "A Complete C++
Example". It is also available on line (maybe with a different version of Example". It is also available on line (maybe with a different version of
Bison): Bison):
https://www.gnu.org/software/bison/manual/html_node/A-Complete-C_002b_002b-Example.html https://www.gnu.org/software/bison/manual/html_node/A-Complete-C_002b_002b-Example.html
@@ -27,7 +31,6 @@ You may pass `-p` to activate the parser debug traces, and `-s` to activate
the scanner's. the scanner's.
<!--- <!---
Local Variables: Local Variables:
fill-column: 76 fill-column: 76
ispell-dictionary: "american" ispell-dictionary: "american"
@@ -50,5 +53,5 @@ GNU General Public License for more details.
You should have received a copy of the GNU General Public License You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>. along with this program. If not, see <http://www.gnu.org/licenses/>.
# LocalWords: mfcalc calc parsers yy MERCHANTABILITY Ctrl ispell american # LocalWords: calc parsers yy MERCHANTABILITY Ctrl ispell american
---> --->

34
examples/c/lexcalc/Makefile Normal file
View File

@@ -0,0 +1,34 @@
# This Makefile is designed to be simple and readable. It does not
# aim at portability. It requires GNU Make.
BASE = lexcalc
BISON = bison
FLEX = flex
XSLTPROC = xsltproc
all: $(BASE)
%.c %.h %.xml %.gv: %.y
$(BISON) $(BISONFLAGS) --defines --xml --graph=$*.gv -o $*.c $<
%.c: %.l
$(FLEX) $(FLEXFLAGS) -o$@ $<
scan.o: parse.h
lexcalc: parse.o scan.o
$(CC) $(CFLAGS) -o $@ $^
run: $(BASE)
@echo "Type arithmetic expressions. Quit with ctrl-d."
./$<
html: parse.html
%.html: %.xml
$(XSLTPROC) $(XSLTPROCFLAGS) -o $@ $$($(BISON) --print-datadir)/xslt/xml2xhtml.xsl $<
CLEANFILES = \
$(BASE) *.o \
parse.[ch] parse.output parse.xml parse.html parse.gv \
scan.c
clean:
rm -f $(CLEANFILES)

28
examples/c/lexcalc/README.md Normal file
View File

@@ -0,0 +1,28 @@
# lexcalc - calculator with Flex and Bison
This directory contains lexcalc, the traditional example of using Flex and
Bison to build a simple calculator.
<!---
Local Variables:
fill-column: 76
ispell-dictionary: "american"
End:
Copyright (C) 2018 Free Software Foundation, Inc.
This file is part of Bison, the GNU Compiler Compiler.
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/>.
--->

27
examples/c/lexcalc/lexcalc.test Normal file
View File

@@ -0,0 +1,27 @@
#! /bin/sh
# Copyright (C) 2018 Free Software Foundation, Inc.
#
# 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/>.
cat >input <<EOF
1+2*3
EOF
run 0 7
cat >input <<EOF
(1+2) * 3
EOF
run 0 9
run -noerr 0 9 -p

32
examples/c/lexcalc/local.mk Normal file
View File

@@ -0,0 +1,32 @@
## Copyright (C) 2018 Free Software Foundation, Inc.
##
## 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/>.
lexcalcdir = $(docdir)/%D%
## ------ ##
## Calc. ##
## ------ ##
check_PROGRAMS += %D%/lexcalc
TESTS += %D%/lexcalc.test
EXTRA_DIST += %D%/lexcalc.test
%C%_lexcalc_SOURCES = %D%/parse.y %D%/parse.h %D%/scan.l
# Don't use gnulib's system headers.
%C%_lexcalc_CPPFLAGS = -I$(top_srcdir)/%D% -I$(top_builddir)/%D%
dist_lexcalc_DATA = %D%/parse.y %D%/scan.l %D%/Makefile %D%/README.md
CLEANFILES += %D%/lexcalc %D%/*.o %D%/parse.c %D%/scan.c
CLEANDIRS += %D%/*.dSYM

95
examples/c/lexcalc/parse.y Normal file
View File

@@ -0,0 +1,95 @@
// Prologue (directives).
%expect 0
// Emitted in the header file, after the definition of YYSTYPE.
%code provides
{
// Tell Flex the expected prototype of yylex.
#define YY_DECL \
enum yytokentype yylex (YYSTYPE* yylval, int *nerrs)
YY_DECL;
void yyerror (int *nerrs, const char *msg);
}
// Emitted on top of the implementation file.
%code top
{
#include <stdio.h> /* printf. */
#include <stdlib.h> /* getenv. */
}
%define api.pure full
%define api.token.prefix {TOK_}
%define api.value.type union
%define parse.error verbose
%define parse.trace
// Error count, exchanged between main, yyparse and yylex.
%param {int *nerrs}
%token
PLUS "+"
MINUS "-"
STAR "*"
SLASH "/"
LPAREN "("
RPAREN ")"
EOL "end-of-line"
EOF 0 "end-of-file"
;
%token <int> NUM "number"
%type <int> exp line
%printer { fprintf (yyo, "%d", $$); } <int>
// Precedence (from lowest to highest) and associativity.
%left "+" "-"
%left "*" "/"
%%
// Rules.
input:
%empty
| input line { printf ("%d\n", $line); }
;
line:
exp EOL { $$ = $1; }
| error EOL { yyerrok; }
;
exp:
exp "+" exp { $$ = $1 + $3; }
| exp "-" exp { $$ = $1 - $3; }
| exp "*" exp { $$ = $1 * $3; }
| exp "/" exp
{
if ($3 == 0)
{
yyerror (nerrs, "invalid division by zero");
YYERROR;
}
else
$$ = $1 / $3;
}
| "(" exp ")" { $$ = $2; }
| NUM { $$ = $1; }
;
%%
// Epilogue (C code).
void yyerror(int *nerrs, const char *msg)
{
fprintf (stderr, "%s\n", msg);
++nerrs;
}
int main (void)
{
int nerrs = 0;
// Enable parser runtime debugging.
if (!!getenv ("YYDEBUG"))
yydebug = 1;
yyparse (&nerrs);
// Exit on failure if there were errors.
return !!nerrs;
}

43
examples/c/lexcalc/scan.l Normal file
View File

@@ -0,0 +1,43 @@
/* Prologue (directives). -*- C++ -*- */
/* Disable Flex features we don't need, to avoid warnings. */
%option nodefault noinput nounput noyywrap
%{
#include <limits.h> /* INT_MIN */
#include <stdlib.h> /* strtol */
#include "parse.h"
%}
%%
/* Rules. */
"+" return TOK_PLUS;
"-" return TOK_MINUS;
"*" return TOK_STAR;
"/" return TOK_SLASH;
"(" return TOK_LPAREN;
")" return TOK_RPAREN;
/* Scan an integer. */
[0-9]+ {
errno = 0;
long n = strtol (yytext, NULL, 10);
if (! (INT_MIN <= n && n <= INT_MAX && errno != ERANGE))
yyerror (nerrs, "integer is out of range");
yylval->TOK_NUM = (int) n;
return TOK_NUM;
}
/* Ignore white spaces. */
[ \t]+ continue;
"\n" return TOK_EOL;
. yyerror (nerrs, "syntax error, invalid character");
<<EOF>> return TOK_EOF;
%%
/* Epilogue (C code). */

1
examples/c/local.mk
View File

@@ -16,5 +16,6 @@
cdir = $(docdir)/%D% cdir = $(docdir)/%D%
dist_c_DATA = %D%/README.md dist_c_DATA = %D%/README.md
include %D%/lexcalc/local.mk
include %D%/mfcalc/local.mk include %D%/mfcalc/local.mk
include %D%/rpcalc/local.mk include %D%/rpcalc/local.mk

2
examples/c/rpcalc/Makefile
View File

@@ -14,7 +14,7 @@ all: $(BASE)
$(CC) $(CFLAGS) -o $@ $< $(CC) $(CFLAGS) -o $@ $<
run: $(BASE) run: $(BASE)
@echo "Type arithmetic expressions in reverse polish notation. Quit with ctrl-d." @echo "Type arithmetic expressions in Reverse Polish Notation. Quit with ctrl-d."
./$< ./$<
html: $(BASE).html html: $(BASE).html