(* Copyright (C) 2005, 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://helm.cs.unibo.it/
 *)

(**** TABLES ****)

(* eq, sym_eq, trans_eq, eq_ind, eq_ind_R *)
let eq_URIs_ref =
 ref [HelmLibraryObjects.Logic.eq_URI,
      HelmLibraryObjects.Logic.sym_eq_URI,
      HelmLibraryObjects.Logic.trans_eq_URI,
      HelmLibraryObjects.Logic.eq_ind_URI,
      HelmLibraryObjects.Logic.eq_ind_r_URI];;

let true_URIs_ref = ref [HelmLibraryObjects.Logic.true_URI]
let false_URIs_ref = ref [HelmLibraryObjects.Logic.false_URI]
let absurd_URIs_ref = ref [HelmLibraryObjects.Logic.absurd_URI]


(**** SET_DEFAULT ****)

exception NotRecognized;;

(* insert an element in front of the list, removing from the list all the
   previous elements with the same key associated *)
let insert_unique e extract l =
 let uri = extract e in
 let l' =
  List.filter (fun x -> let uri' = extract x in not (UriManager.eq uri uri')) l
 in
  e :: l'

let set_default what l =
 match what,l with
    "equality",[eq_URI;sym_eq_URI;trans_eq_URI;eq_ind_URI;eq_ind_r_URI] ->
      eq_URIs_ref :=
       insert_unique (eq_URI,sym_eq_URI,trans_eq_URI,eq_ind_URI,eq_ind_r_URI)
        (fun x,_,_,_,_ -> x) !eq_URIs_ref
  | "true",[true_URI] ->
      true_URIs_ref := insert_unique true_URI (fun x -> x) !true_URIs_ref
  | "false",[false_URI] ->
      true_URIs_ref := insert_unique false_URI (fun x -> x) !false_URIs_ref
  | "absurd",[absurd_URI] ->
      absurd_URIs_ref := insert_unique absurd_URI (fun x -> x) !absurd_URIs_ref
  | _,_ -> raise NotRecognized

(**** LOOKUP FUNCTIONS ****)

let eq_URI () = let eq,_,_,_,_ = List.hd !eq_URIs_ref in eq

let is_eq_URI uri =
 List.exists (fun (eq,_,_,_,_) -> UriManager.eq eq uri) !eq_URIs_ref

let sym_eq_URI ~eq:uri =
 try
  let _,x,_,_,_ = List.find (fun eq,_,_,_,_ -> UriManager.eq eq uri) !eq_URIs_ref in x
 with Not_found -> raise NotRecognized

let trans_eq_URI ~eq:uri =
 try
  let _,_,x,_,_ = List.find (fun eq,_,_,_,_ -> UriManager.eq eq uri) !eq_URIs_ref in x
 with Not_found -> raise NotRecognized

let eq_ind_URI ~eq:uri =
 try
  let _,_,_,x,_ = List.find (fun eq,_,_,_,_ -> UriManager.eq eq uri) !eq_URIs_ref in x
 with Not_found -> raise NotRecognized

let eq_ind_r_URI ~eq:uri =
 try
  let _,_,_,_,x = List.find (fun eq,_,_,_,_ -> UriManager.eq eq uri) !eq_URIs_ref in x
 with Not_found -> raise NotRecognized

let true_URI () = List.hd !true_URIs_ref
let false_URI () = List.hd !false_URIs_ref
let absurd_URI () = List.hd !absurd_URIs_ref