List Shuffle in StandardML/NJ

list_shuffle.sml

fun shuffle xs = let
  val rand = let
    val seed = let
      val  max = IntInf.fromInt (
        case(Int.maxInt) 
          of (Option.SOME max) => max 
           |  Option.NONE      => raise Fail("Can't get Int.maxInt")
      );
      val time = Time.now ();
      val (_, seed1) = IntInf.divMod (Time.toSeconds      time, max);
      val (_, seed2) = IntInf.divMod (Time.toMilliseconds time, max);
    in (IntInf.toInt seed1, IntInf.toInt seed2) end;
  in Random.rand seed end;
  
  val ys = List.tabulate (List.length xs, fn n => Random.randInt rand);
  fun pred ((p, q), (r, s)) = if q = s then EQUAL else (if q < s then LESS else GREATER);
  val zs = qsort pred (ListPair.zip (xs, ys));
in List.map (fn (p, q) => p) zs end;

val xs = shuffle (List.tabulate (16, fn n => n + 1));