data List a = { Nil, Cons a (List a) }
data Bool = { True, False }
defn length l = {
    case l of {
        Nil -> { 0 }
        Cons x xs -> { 1 + length xs }
    }
}
defn main = { length (Cons 1 (Cons 2 (Cons 3 Nil))) + length (Cons True (Cons False (Cons True Nil))) }
