(* fil : Pivot-Filter fŸr QuickSort *)

let rec fil p l = match l with
    (x::xs) -> if (p x) then x::(fil p xs) else fil p xs
  | [] -> [];;

(* qs : QuickSort *)

let rec qs l = match l with
    (x::xs) -> qs (fil (function z -> z <  x) xs) @ [x] @
               qs (fil (function z -> z >= x) xs)
  | [] -> [];;