Haskell: first steps

length.hs

main :: IO()

len :: [a] -> Int

len [] = 0
len (_:xs) = 1 + len xs

main = putStrLn $ "The length is: " ++ show (len [1, 2, 3, 4, 5])

reverse.hs

main :: IO()

reverse' :: [a] -> [a]

reverse' [x] = [x]
reverse' (x:xs) = reverse' xs ++ [x]

main = putStrLn $ "The reverse is: " ++ show (reverse' [1, 2, 3])