"half 8 >>= half" might look a lot different from "half . half $ 8", but they're actually identical in underlying structure! The monad version is just using the

"half 8 >>= half" might look a lot different from "half . half $ 8", but they're actually identical in underlying structure! The monad version is just using the wrong operator for visual comparison. (.) composes two functions[1] but (>>=) composes a monad value with a monad function[2]. It'd be nice if we had an operator to compose two monad functions instead. We can define that operator in terms of (>>=): "g <=< f = \x -> f x >>= g". You can check that the types work out[3]. Notice the great similarity to (.). (It's because they're both categorical composition operators of functions.) Now we can write "half <=< half $ 8" and everything's dandy. [1]: (.) :: (b -> c) -> (a -> b) -> (a -> c) [2]: (>>=) :: m a -> (a -> m b) -> m b [3]: (<=<) :: (b -> m c) -> (a -> m b) -> (a -> m c)