Thread: Intro to C programming help

I am trying to figure out how to convert this recursive Scheme definition into a non-recursive loop function in C. I've just started learning C after Scheme and loops are still confusing to me.

This is the recursive version in scheme:

Code:

#lang racket
(define (powmod2 x e m)
  (define xsqrm (remainder (* x x) m))
  (cond 
    [(= e 0) 1]
    [(even? e) (powmod2 xsqrm (/ e 2) m)]
    [(odd? e) (remainder (* x (powmod2 xsqrm (/ (sub1 e) 2) m)) m)]))

This is my non-working code in C:

Code:

int powmod2(int x, int e, int m) {
   int ans = 1;
   while (e != 0) {
      x=x*x%m;
      if(e%2 == 0) {
         e=e/2;
      }
      else {
         e=(e-1)/2;
         ans=(ans*x)%m;
      }
    }
    return ans;
}

Any guidance would really be appreciated!