Yacc.txt

CALCULATOR 

LEX PART:

%{

#include<stdio.h>

#include "y.tab.h"

extern int yylval;

%}



%%

[0-9]+ {

          yylval=atoi(yytext);

          return NUMBER;

       }

[\t] ;

[\n] return 0;

. return yytext[0];

%%

int yywrap()

{

return 1;

}

YACC PART:

%{

    #include<stdio.h>

    int flag=0;

   

%}

%token NUMBER



%left '+' '-'

%left '*' '/' '%'

%left '(' ')'

%%

ArithmeticExpression: E{

         printf("\nResult=%d\n",$$);

         return 0;

        };

E:E'+'E {$$=$1+$3;}

 |E'-'E {$$=$1-$3;}

 |E'*'E {$$=$1*$3;}

 |E'/'E {$$=$1/$3;}

 |E'%'E {$$=$1%$3;}

 |'('E')' {$$=$2;}

 | NUMBER {$$=$1;}

;

%%



void main()

{

   printf("\nEnter Any Arithmetic Expression which can have operations Addition, Subtraction, Multiplication, Divison, Modulus and Round brackets:\n");

   yyparse();

  if(flag==0)

   printf("\nEntered arithmetic expression is Valid\n\n");

 

}

void yyerror()

{

   printf("\nEntered arithmetic expression is Invalid\n\n");

   flag=1;

}


To write a YACC program to recognize that a valid variable which starts with a letter

followed by any number of letters or digits.





LEX PART:



%{



    #include "y.tab.h"



%}



%%

[a-zA-Z_][a-zA-Z_0-9]* return letter;

[0-9]                       return digit;

.                      return yytext[0];

\n                     return 0;

%%

int yywrap()

{

return 1;

}

YACC PART:

%{

    #include<stdio.h>

    int valid=1;

%}

%token digit letter

%%

start : letter s

s :     letter s

      | digit s

      |

      ;

%%

int yyerror()

{

    printf("\nIts not a identifier!\n");

    valid=0;

    return 0;

}

int main()

{

    printf("\nEnter a name to tested for identifier ");

    yyparse();

    if(valid)

    {

        printf("\nIt is a identifier!\n");

    }

}