[Gajurgensen]

Let's say getting those n and m values has a nasty type like `getNM :: IO (Maybe (Int, Int))`. All you need to do is map twice when using the original function.

  foo (n, m) = take n . filter p . drop m

  bar = fmap (fmap foo) getNM

It's a little awkward, but no major refactor. A small price to pay for the nice types we get. I'd argue that if other languages make dealing with IO and optional values easier, its because they don't bother restricting IO (not necessarily criticizing that), or they don't bother checking completeness over optionals (i.e. a stray `null` can show up anywhere and derail the program, which I do think is a bad thing). Overall, Haskell provides many powerful tools for composing complex types, such as the functor/applicative/monad classes.