Cons!

cons.hs

data List a =
  Empty |
  Cons a (List a)
  deriving (
    Eq,
    Ord
  )

-- Type classes are pretyy cool

instance (Show a) => Show (List a) where
  show Empty = "()"
  show (Cons x xs) = "(" ++ (show x) ++ " " ++ (show xs) ++ ")"

car :: List a -> a
car Empty = error "car called on empty List."
car (Cons h _) = h

cdr :: List a -> List a
cdr Empty = error "cdr called on empty List."
cdr (Cons _ t) = t