lily/programs/sum.lily

data IntList = { Nil, Cons(Int, IntList) }
defn sum l = {
    case l of {
        Nil -> { 0 }
        Cons(x, xs) -> { x + sum xs }
    }
}
defn main = { sum (Cons 1 (Cons 2 (Cons 3 (Cons 4 Nil)))) }