9. Program in 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)

/*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 of the Above Program.
Program in YACC to evaluate an expression (simple calculator program for addition and
subtraction, multiplication, division)