data List a where 
    Nil  : List a
    Cons : a -> List a -> List a

map : (a -> b) -> List a -> List b
map f xs = case xs of
    Nil       => Nil
    Cons x xs => Cons (f x) (map f xs)

sum : List Int -> Int
sum xs = case xs of
    Nil       => 0
    Cons x xs => x + (sum xs)

main = let y = 10 in sum (map (\x. x + y) (Cons 2 (Cons 4 Nil)))