Yolo.hs

{-# LANGUAGE GADTs #-}
module Yolo where

import System.IO.Unsafe

class Yolo f where
  yolo :: f a -> a

instance Yolo Maybe where
  yolo (Just x) = x

instance Yolo (Either a) where
  yolo (Right x) = x

instance Yolo ([]) where yolo = head

data ReadMe a = Read a => ReadMe String

instance Yolo ReadMe where
    yolo (ReadMe s) = read s


instance Yolo IO where
  yolo = unsafePerformIO


-- > yolo (Just 3)
-- 3
-- > yolo (Right 3)
-- 3
-- > take 5 $ yolo (readFile "Yolo.hs")
-- "{-# L"}"
-- > yolo (ReadMe "5" :: ReadMe Int)
-- 5

Thanks @edofic :)

import Control.Monad.Trans.Except
import Control.Monad.Trans.Maybe
import Control.Monad.Trans.Writer
import Control.Monad.Trans.Identity
import Data.Functor.Identity

instance Yolo m => Yolo (ExceptT e m) where
  yolo (ExceptT act) = yolo . yolo $ act

instance Yolo m => Yolo (MaybeT m) where
  yolo (MaybeT act) = yolo . yolo $ act

instance Yolo m => Yolo (WriterT w m) where
  yolo (WriterT act) = fst . yolo $ act

instance Yolo f => Yolo (IdentityT f) where
  yolo (IdentityT act) = yolo $ act

instance Yolo Identity where
  yolo (Identity act) = act