pub fn unzip(xs: List<(a, b)>) -> (List<a>, List<b>) {
when xs is {
[] ->
([], [])
[(a, b), ..rest] -> {
let (a_tail, b_tail) =
unzip(rest)
([a, ..a_tail], [b, ..b_tail])
}
test unzip_1() {
unzip([(1, "a"), (2, "b")]) == ([1, 2], ["a", "b"])