27/27.14-strict-list.hs

{-# LANGUAGE Strict #-}

module StrictList where

data List a = Nil
            | Cons a (List a)
            deriving Show

take' n _           | n <= 0 = Nil
take' _ Nil         = Nil
take' n (Cons x xs) = (Cons x (take' (n - 1) xs))

map' _ Nil         = Nil
map' f (Cons x xs) = (Cons (f x) (map' f xs))

repeat' x = xs where xs = (Cons x xs)

main = do
  print $ take' 10 $ map' (+1) (repeat' 1)