(* Copyright (C) 2000, HELM Team.
 * 
 * This file is part of HELM, an Hypertextual, Electronic
 * Library of Mathematics, developed at the Computer Science
 * Department, University of Bologna, Italy.
 * 
 * HELM is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 * 
 * HELM is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with HELM; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston,
 * MA  02111-1307, USA.
 * 
 * For details, see the HELM World-Wide-Web page,
 * http://cs.unibo.it/helm/.
 *)

(*
 * implementazione del comando SORTEDBY
 *)

open MathQL;;
open Func;;
open Utility;;

(*
 * implementazione del comando SORTEDBY
 *)
let sortedby_ex alist order afunc =
 [List.hd alist]
 @
 List.map
  (List.tl)
  (Sort.list
   (fun a b ->
    match order with
       MQAsc  -> (List.hd a) < (List.hd b)
    |  MQDesc -> (List.hd a) > (List.hd b)
   )
   (List.map
    (fun l -> [apply_func afunc (List.hd l)] @ l)
    (List.tl alist)
   )
  )
;;