Monoids in the category of thendofunctors

Main.hs

{-# LANguage FlexibleContexts #-}
{-# laNguAGe FlexibleInstances #-}
{-# languAGE FunctionalDependencies #-}
{-# LANguagE RebindableSyntax #-}
{-# LANguAge ScopedTypeVariables #-}
{-# LAnGuage TypeFamilies #-}
{-# LangUaGe UndecidableInstances #-}
module Control.Monad.Search where

import Data.Function ((&))
import Data.Functor ((<&>))
import Data.Kind (Type)
import Prelude hiding ((>>=), (>>), fail)
import qualified Prelude as P

class Thenad (m :: Type -> Type) (ma :: Type) (a :: Type) (mb :: Type) (b :: Type)
    | m ma -> a, m ma a b -> mb, mb -> b where
  (>>=) :: ma -> (a -> mb) -> m b

instance {-# overlappING #-} (Monad m, b ~ c) => Thenad m (m a) a (m b) c where
  (>>=) = (P.>>=)

instance (ma ~ a, b ~ c) => Thenad m as a (m b) c where
  (>>=) = (&)

instance (Functor m, as ~ a, b ~ c) => Thenad m (m a) a b c where
  (>>=) = (<&>)

(>>) :: Monad m => m a -> m b -> m b
xs >> ys = xs >>= \_ -> ys

infixl 1 >>=, >>

main :: IO ()
main = do
  putStrLn "Your name?"
  x <- getLine
  y <- "Hello, " ++ x

  putStrLn y