(* 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/.
 *)

(*  AUTOR: Ferruccio Guidi <fguidi@cs.unibo.it>
 *)

module I = MathQL.I

(* strings ******************************************************************)

let avs_of_string s = I.make s I.grp_empty 

let string_of_avs r =
   match I.peek r with 
      | I.Single (s, _) -> Some s
      | _               -> None

(* boolean constants  *******************************************************)

let bool_of_avs r = r <> I.empty

let avs_of_bool = function
   | true  -> I.make "" I.grp_empty
   | false -> I.empty

let val_false = avs_of_bool false

let val_true = avs_of_bool true

(* iterators ****************************************************************)

let grp_iter f al =
   List.fold_left (fun s a -> I.grp_union s (f a)) I.grp_empty (List.rev al)

let grp_iter2 f al bl = 
   List.fold_left2 (fun s a b -> I.grp_union s (f a b)) 
                   I.grp_empty (List.rev al) (List.rev bl)

let iter f al = List.fold_left (fun s a -> I.union s (f a)) 
                               I.empty (List.rev al)

(* other ********************************************************************)

let grp_make_x p vl = grp_iter (I.grp_make p) vl

let x_grp_make_x p rs = 
   let aux g s _ = I.grp_union g (I.grp_make p s) in
   I.iter aux I.grp_empty rs

let make_x s gl = 
   if gl = [] then avs_of_string s else iter (I.make s) gl

let count v = I.iter (fun n _ _ -> succ n) 0 v

let subj v = iter (fun s -> I.make s I.grp_empty) v

(* numeric operations *******************************************************)

exception NumberError of MathQL.result

let avs_of_int i = I.make (string_of_int i) I.grp_empty

let int_of_avs r =
   try match (I.peek r) with 
      | I.Empty
      | I.Many _        -> raise (Failure "int_of_string")
      | I.Single (s, _) -> MQueryUtil.int_of_string s
   with Failure "int_of_string" -> raise (NumberError r)