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 a as => Cons (f a) (map f as)

add : Int -> Int -> Int
add x y = x + y

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

main : Int
main = sum (map (add 1) (Cons 4 (Cons 3 (Cons 2 (Cons 1 Nil)))))