It's funny you should ask this, because you're right that some types really are quite hard to read and there was a great discussion a few days ago where someone

It's funny you should ask this, because you're right that some types really are quite hard to read and there was a great discussion a few days ago where someone mentioned that the types tell you a lot about what the function is doing, and then someone retorted that most examples of types guiding you are usually very simple, and posted a really complex type for people to decipher, and the more proficient Haskellers actually worked it out--based partly on their previous knowledge of similar types! See http://www.reddit.com/r/haskell/comments/3ijtej/any_tips_for_reading_haskell_code/cuh36rm http://www.reddit.com/r/haskell/comments/3ijtej/any_tips_for... Now, I'm not at that level of proficiency, but I can tell that your example above takes a binary function and 'lifts' it into a higher (monadic) context, so that it can work on monadic values. And the reason I can work this out is because I know about the Functor typeclass which has the function fmap :: (a -> b) -> f a -> f b, which does a similar job of lifting an input function into a higher context (in this case a functor context).