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Lex & yacc Programming in linux.
Hi,
I developed an application using lex & yacc. It is a simple calculator which does add, subtract and multiplication. The program is compiled correctly without errors. But when i execute the program, it is giving 0 as output irrespective of input and the result is always 0.000. For example if the input is 3.2 + 4.5, the output is 0.000. I dont know where i have gone wrong. The programs are given below.
cal.l
------
%{
#include "global.h"
#include "y.tab.h"
#include <stdlib.h>
%}
white [ \t]+
digit [0-9]
integer {digit}+
real {integer}("."{integer})?
%%
{white} { }
{real} {yyval=atof(yytext);
return (NUMBER);}
"+" return (PLUS);
"-" return (MINUS);
"*" return (TIMES);
"\n" return (END);
-------------------------------------------------
cal.y
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%{
#include "global.h"
#include <stdio.h>
#include <stdlib.h>
%}
%token NUMBER
%token PLUS MINUS TIMES
%token END
%left PLUS MINUS TIMES
%start Input
%%
Input:
| Input Line
;
Line:
END
| Expression END {printf("\n Result: %f",$1);}
;
Expression:
NUMBER { $$=$1; }
| Expression PLUS Expression { $$=$1+$3;}
| Expression MINUS Expression { $$=$1-$3; }
| Expression TIMES Expression { $$=$1*$3; }
;
%%
int yyerror(char *s)
{
printf("%s\n",s);
}
int main(void)
{
yyparse();
}
global.h
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#define YYSTYPE double
extern YYSTYPE yyval;
Result:
-------
[root@mycal]# yacc -d cal.y
[root@mycal]# lex cal.l
[root@mycal]# gcc -o cal y.tab.c lex.yy.c -lfl
[root@mycal]# ./cal
2.3+4.2
Result: 0.000000
[root@mycal]#
Let know what is the problem and how to solve it.
Thanx.
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