say if I want to sum a list of numbers but only until it hits a max limit.
Currently, I control it through the function and basically do nothing when the max is hit. However, if the list is very long, would this mean the same function would be called for the rest of the list which can be a waste of cycle ? In an imperative language, I just break/return in the middle of the loop.
If you are using foldl or foldl', then yes, the definition tells you that 'foldl' itself will be applied as many times as the length of the list: foldl f z [] = z foldl f z (x:xs) = foldl f (f z x) xs For your situation, foldr is better: foldr f z [] = z foldr f z (x:xs) = f x (foldr f z xs) The function 'f' is the outermost application, therefore it can decide to ignore its second argument, meaning that the recursive call to foldr is never computed. Regards, Malcolm