I apologize if this is a bit off-topic -- I'm asking it here because if what I want to do is possible, it may only be possible with ghc extensions, as opposed to vanilla Haskell...... In many types of applications, it's common to have a loop which loops infinitely, of at least until some condition is met. For example, in C-like syntax: for (;;;) { a = get_input(); if (a == GET_OUT) break; do_comthing(); } the above code could be used in an input-processing loop. The question is, is something like this possible in Haskell? I realize that you can use recursive calls to do something similar: f a | a == GET_OUT = a | otherwise = f ( g a) The problem is stack-growth. I can't figure out a way (I'm sort of a newbie) to so something like the above without growing my stack infinitely. I've seen something called "tail-recursion" discussed in comp.lang.functional that *may* be relevant, but I can't find any concise explanation of this concept. So, is this possible in either Haskell or Haskell+ghc extensions? TIA, Mark.