fun iter_ (vec: [int]) (fn: |int| -> int) (current: int): void = do
    if current == @len(vec) then
        do end
    else
        do
            @get(vec, current)
            |> fn(_)
            |> @write(_)
            @write("\n")

            iter_(vec, fn, current + 1)
        end
    end
end

fun iter (vec: [int]) (fn: |int| -> int): void = iter_(vec, fn, 0)

fun mul10 (x: int): int = x * 10

fun main: void = do
    let foo: [int] = [69, 420, 727, 1337, 42069, 69420]
    iter(foo, mul10)
end