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examples: add a simple Flex+Bison example in C

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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
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43
examples/c/lexcalc/scan.l Normal file
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/* 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). */