Middle of a list with the hare and tortoise method

middle.hs

-- | Main entry point to the application.
module Main where

-- | The main entry point.
main :: IO ()
main = do
    putStrLn "Welcome to FP Haskell Center!"
    putStrLn "Have a good day!"
    putStrLn $ show $ middle [1]
    putStrLn $ show $ middle [1,2]
    putStrLn $ show $ middle [1,2,3]
    putStrLn $ show $ middle [1,2,3,4]
    putStrLn $ show $ middle [1,2,3,4,5]

middle :: [a] -> a  
middle [x] = x
middle [x,y] = x
middle l = middle' l l

middle' :: [a] -> [a] -> a
middle' [] (x:l) = x
middle' [_] (x:l) = x
middle' (_:_:hare) (_:tortoise) = middle' hare tortoise