Hi, I am a newbie learning Haskell. I have used languages with functional features before (R, Scheme) but not purely functional ones without side-effects. Most of the programming I do is numerical (I am an economist). I would like to know how to implement the iterative algorithm below in Haskell. f is an a->a function, and there is a stopping rule goOn(a,anext) :: a a -> Bool which determines when to stop. The algorithm looks like this (in imperative pseudocode): a = ainit while (true) { anext <- f(a) if (goOn(a,anext)) a <- anext else stop and return anext } For example, f can be a contraction mapping and goOn a test based on the metric. I don't know how to do this in a purely functional language, especially if the object a is large and I would like it to be garbage collected if the iteration goes on. Thank you, Tamas