https://www.reddit.com/r/haskell/comments/52o8yf/how_can_i_make_this_generic/

IOEffect.hs

{-# LANGUAGE GADTs #-}

class IOEffect x where
  runIOEffect :: x a -> IO a

data M a where
  Pure :: a -> M a
  Ap :: M (a -> b) -> M a -> M b
  Bind :: M a -> (a -> M b) -> M b
  M :: IOEffect x => x a -> M a

instance Functor M where
  fmap f s = Bind s (\a -> Pure $ f a)

instance Applicative M where
  pure a = Pure a
  (<*>) f a = Ap f a

instance Monad M where
  (>>=) a mb = Bind a mb

runM :: M a -> IO a
runM (Pure a) = return a
runM (Ap f a) = (runM f) <*> (runM a)
runM (Bind s fs) = (runM s) >>= (\a -> runM (fs a))
runM (M xa) = runIOEffect xa

---

data ConsoleIO a where
  WriteIO :: String -> ConsoleIO ()
  ReadLineIO :: ConsoleIO String

instance IOEffect ConsoleIO where
  runIOEffect (WriteIO s) = putStr s
  runIOEffect ReadLineIO = getLine

---

program :: M ()
program = do
  M $ WriteIO "Enter a number: "
  x <- M ReadLineIO
  M $ WriteIO "Enter another one: "
  y <- M ReadLineIO
  let z = show (read x * read y)
  M $ WriteIO $ x ++ " * " ++ y ++ " = " ++ z ++ "\n"

main :: IO ()
main = runM program