(*------------------------------------------------------------*)

fun foldl f d ( nil     ) = d
  | foldl f d ( x :: xs ) = foldl f ( f d x ) xs

fun filter p = foldl ( fn a => fn c => if p c then c :: a else a ) nil

fun sort ( nil     ) = nil
  | sort ( x :: xs ) =
      let
          val left  = filter ( fn v => v <  x ) xs
          val right = filter ( fn v => v >= x ) xs
      in
          sort left @ x :: sort right
      end

(*------------------------------------------------------------*)

fun showList ( nil     ) = "\n"
  | showList ( x :: xs ) = Int.toString x ^ " " ^  showList xs

val printList = print o showList

(*------------------------------------------------------------*)

val arr = [ 3, 2, 3, 7, 2, 1, 0, 7 ]

val _ =
  let
      val srt = sort arr
  in
      ( printList arr
      ; printList srt
      )
  end

(*------------------------------------------------------------*)