Kind2/base/List/split.kind

// # Take n elements of a list and return the rest of the list as a pair.
// - List.split([1, 2, 3], 2) == ([1, 2], [3])
// - List.split(xs, n) == (List.take(xs, n), List.drop(xs, n))

List.split<A: Type>(xs : List<A>, n : Nat) : Pair<List<A>, List<A>>
  case n {
    zero : {[], xs}
    succ : case xs {
      nil : {[], xs}
      cons :
       let {xs, ys} = List.split(A, xs.tail, n.pred)
       {List.cons(A, xs.head, xs), ys}
    }
  }