The type-level S combinator in Haskell.

ess

A type-level S Combinator for Haskell.

I will be deeply impressed if anyone finds a use for this.

Why does it exist? We have a type-level I combinator in the Identity monad.

newtype Identity a = Identity {runIdentity :: a}

We also have a type-level K combinator in the Const functor.

newtype Const a b = Const {getConst :: a}

But where is our S combinator? More importantly, is it useful at all? This repository exists, because I want to know.