(* file: sublists.ml
 * author: Bob Muller
 *
 * CS1101 Computer Science I
 *
 * The sublist example. Illustrates:
 * 1. recursion - solving the problem by patching up a solution to a
 *                smaller instance of the problem.
 * 2. map
 * 3. anonymous functions
 *
 * sublists : 'a list -> ('a list) list
 *)
let rec sublists xs =
  match xs with
  | [] -> [[]]
  | x :: xs -> let ans = sublists xs in
               let newPart = List.map (fun ys -> x :: ys) ans
               in
               ans @ newPart