List recursions

Main.hs

module Main where

import Control.Monad
import Control.Arrow
import System.IO.Unsafe

{-Without pattern matching-}
version1 :: IO()
version1 = pr [1..5]
 where
   pr :: (Show a) => [a] -> IO ()
   pr xs = unless (null xs) (print (head xs) >> pr (tail xs))

{-With Control monad-}
version2 :: IO()
version2 = mapM_ print [1..5]

{-With Control monad and applicatives functor-}
version3 :: IO()
version3 = sequence_ (fmap print [1..5])

{-With list comprehension-}
version4 :: IO()
version4 = sequence_ [print a | a <- [1..5] ]

{-With list monad and some wtf -}
{- Only those who bear the name of Simon can use unsafePerformIO -}
version5 :: IO()
version5 = when (all (<5) lst) (return lst >> return () )
 where lst = [1..5] >>=  \a -> return (unsafePerformIO (print a >> return a) )

{-Display of results-}

printer :: [IO()]
printer = map (show >>> ("version"++) >>> print) [1..5]

main :: IO()
main = mapM_ (\(a, b) -> a >> b) $ zip printer [version1, version2,
version3, version4, version5]