S6 CSE COMPILER LAB : INFIX TO POSFIX CONVERSION

/*  INFIX TO POSFIX CONVERSION   */

Yacc program

%{

#include<stdio.h>

int top=0;

char stack[50];

%}

%token id digit

%left '+''-'

%left '*''/'

%left '^'

%nonassoc UMINUS

%%

S:E

E:E'+' {push();}T {pop();}

 |E'-' {push();}T {pop();}

 |T

    ;

T:T'*' {push();}F {pop();}

 |T'/' {push();}F {pop();}

 |T'^' {push();}F {pop();}

 |F

   ;

F:id {print();}

 |digit {print();}

 |'('E')'

 ;

%%

#include"lex.yy.c"

int main()

{

 yyparse();

yylex();

return 0;

}

yyerror(char *s)

{

printf("\n error \n");

}

push()

{

top++;

stack[top]=yytext[0];

}

pop()

{

printf("%c",stack[top]);

top--;

}

print()

{

printf("%c",yytext[0]);

}

Lex program

%{

#include "y.tab.h"

%}

%%

[0-9]+   {return digit;}

[a-z]+   {return id;}

[\t]     ;

[\n]     {return 0;}

.        {return yytext[0];}

%%

 OUTPUT

a+b

ab+  

a*b-c/2

ab*c2/-

p+3*a-q

p3a*+q-