list dot

listdot.hs

{-# LANGUAGE FlexibleInstances #-}
{-# LANGUAGE FunctionalDependencies #-}
{-# LANGUAGE MultiParamTypeClasses #-}

class ListDot t a | t -> a where
  (•) :: ([a] -> [a]) -> a -> t

instance ListDot ([a] -> [a]) a where
  (f • x) xs = f (x : xs)

instance ListDot [a] a where
  f • x = f [x]

list :: [a] -> [a]
list = id

x :: [Int]
x =
  list
    • 1
    • 2
    • 3