YACC to evaluate an expression (simple calculator program for addition and subtraction, multiplication, division)

/*Program in YACC to evaluate an expression (simple calculator program for addition and

subtraction, multiplication, division).*/

File Name : calc10.y

%{

 #include<stdio.h>

int yylex(void);

int yyerror(char *);

%}

%token NAME NUMBER

%%

statement : NAME '=' expression

 | expression { printf("=%d\n",$1);}

 ;

expression:expression'+' NUMBER{$$ = $1+$3;}

 |expression '-' NUMBER {$$ = $1-$3;}

 |expression '*' NUMBER {$$ = $1*$3;}

 |expression '/' NUMBER { if ($3!=0){ $$ = $1/$3; }else { printf("Error: divide by Zero"); } }

 |NUMBER {$$=$1;}

 ;

%%

int main()

{

yyparse();

return 0;

}

int yyerror(char *s)

{

 printf("%s",s);

}

File Name : calc10.l

%{

 #include "y.tab.h"

 extern int yylval;

%}

%%

[0-9]+ { yylval=atoi(yytext);return NUMBER;}

\n  {return 0;}

.   {return yytext[0];}

%%

Output: