recursive --> iteration

hello /prog/, yes this is basically homework help...

I have a C function that computes the eth power of a number x, modulo another number m, where e is very large. The function uses recursion to do so. I need to implement the program using iteration. I've attempted it and i'm really stuck here, i provided both functions in this paste: http://pastebin.com/ayb87BBr

can someone please point out my stupid mistakes?


powmod2 :: Integral -> Integral -> Integral -> Integral
powmod2 _ 0 _ = 1
powmod2 x e m =
    if e `mod` 2 == 0 then
        powmod2 xsqrm (e / 2) m
    else
        x * $ powmod2 xsqrm (--e)/2 m % m;
    where xsqrm = (x*x)%m;
So, why doesn't everyone use Haskell?