How can a while loop be simulated in a functional language like haskell?

I don't know Haskell, but there is one thing that should still be valid for a functional language: Iteration (loops) can always be replaced by an equivalent recursion or vice versa.

The least confusing definition of recursion[^] is a function that calls itself. Each call represents an iteration of the original loop. Endless recursion does not work (it usually ends in a stack overflow), therefore there must be some condition that ends the recursion and simply returns.

For a 'while type' recursion, you would have to test your condition in order to decide wether to execute your function or to return. This is C-like pseudocode:

ReturnType RecursiveFunction(SomeParameters)
{
    if(Condition == true)
    {
        return;
    }
    else
    {
        // Do whatever your loop should have done,
        // possibly modifying the parameters that have been passed.

        // recursive call to your function
        return RecursiveFunction(ModifiedParameters);
    }
}

Perhaps this link can help:
Recursion - Learn You a Haskell for Great Good![^]