Use cases for functor/applicative/monad instances for functions

Question

Haskell has Functor, Applicative and Monad instances defined for functions (specifically the partially applied type (->) a

Answer 1

here an application of the bind function that I used for solving the Diamond Kata. Take a simple function that mirrors its input discarding the last element

mirror :: [a] -> [a]
mirror xs = xs ++ (reverse . init) xs

let's rewrite it a bit

mirror xs = (++) xs ((reverse . init) xs)
mirror xs = flip (++) ((reverse . init) xs) xs
mirror xs = (reverse . init >>= flip (++)) xs
mirror = reverse . init >>= flip (++)

Here is my complete implementation of this Kata: https://github.com/enolive/exercism/blob/master/haskell/diamond/src/Diamond.hs