Native idiom brackets

gistfile1.txt

-- https://wiki.haskell.org/Idiom_brackets

{-# LANGUAGE MultiParamTypeClasses, FunctionalDependencies, FlexibleContexts, FlexibleInstances, UndecidableInstances #-}
import Control.Applicative
import Control.Monad.Identity

class Applicative i => Idiomatic i f g | g -> f i where
   idiomatic :: i f -> g
 
iI :: Idiomatic i f g => f -> g
iI = idiomatic . pure
 
data Ii  =  Ii
 
instance Applicative i    => Idiomatic i x (Ii -> i x) where
  idiomatic xi Ii     = xi
 
instance Idiomatic i f g  => Idiomatic i (s -> f) (i s -> g) where
  idiomatic sfi si    = idiomatic (sfi <*> si)

f :: Identity Int
f = iI (+) (Identity 5) (Identity 6) Ii

Wow...