binary to decimal conversion - yacc program

 bindec.lex

***************************************

%{

/* Definition section */

#include<stdio.h>

#include<stdlib.h>

#include"bindec.tab.h"

extern int yylval;

%}

%option noyywrap

/* Rule Section */

%%

0 {yylval=0;return ZERO;}

1 {yylval=1;return ONE;}

[ \t] {;}

\n return 0;

. return yytext[0];

%%

bindec.y

********************************************

%{

/* Definition section */

#include<stdio.h>

#include<stdlib.h>

%}

%token ZERO ONE

/* Rule Section */

%%

N: L {printf("The decimal is=%d\n", $$);}

L: L B {$$=$1*2+$2;}

   | B {$$=$1;}

B: ZERO {$$=$1;}

   |ONE {$$=$1;};

%%

//driver code

int main()

{

while(yyparse());

}

int yyerror(char *s)

{

printf("\n Invalid Expression \n");

}

Execution

*************************

$ bison -d bindec.y

$ flex bindec.lex

$ gcc lex.yy.c bindec.y.c

$ ./a.out

101101

The decimal is=45