exp.l file
%option noyywrap
%{
#include<stdio.h>
#include "y.tab.h"
%}
%%
[0-9]+|[0-9]+\.[0-9]+
{yylval.dval=atof(yytext);return DIGIT;}
.|\n {return
yytext[0];}
%%
exp.y file
%{
#include<stdio.h>
%}
%union
{
double dval;
}
%token <dval> DIGIT
%type <dval> expr
%type <dval> term
%type <dval> factor
%%
line: expr '\n' {printf("%lf\n",$1);};
expr: expr '+' term {$$=$1 + $3 ;} | expr '-'
term {$$=$1 - $3 ;}| term;
term: term '*' factor {$$=$1 * $3 ;} | term '/'
factor {$$=$1 / $3 ;} | factor;
factor: '(' expr ')' {$$=$2 ;} | '-'factor {$$=
-$2;} | DIGIT;
%%
int main()
{
yyparse();
}
int yyerror(char *s)
{
printf("%s",s);
return 0;
}
Output:
