(* 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://cs.unibo.it/helm/.
 *)


type 'a path_string_elem = 
  | Constant of 'a * int (* name, arity *)
  | Bound of int * int (* rel, arity *)
  | Variable (* arity is 0 *)
  | Proposition (* arity is 0 *) 
  | Datatype (* arity is 0 *) 
  | Dead (* arity is 0 *) 
;;  

type 'a path = ('a path_string_elem) list;;

module type Indexable = sig
  type input
  type constant_name
  val compare: 
    constant_name path_string_elem -> 
    constant_name path_string_elem -> int
  val string_of_path : constant_name path -> string
  val path_string_of : input -> constant_name path
end

module type DiscriminationTree  =
    sig

      type input 
      type data
      type dataset
      type constant_name
      type t

      val iter : t -> (constant_name path -> dataset -> unit) -> unit
      val fold : t -> (constant_name path -> dataset -> 'b -> 'b) -> 'b -> 'b

      val empty : t
      val index : t -> input -> data -> t
      val remove_index : t -> input -> data -> t
      val in_index : t -> input -> (data -> bool) -> bool
      val retrieve_generalizations : t -> input -> dataset
      val retrieve_unifiables : t -> input -> dataset

      (* the int is the number of symbools that matched, note that
       * Collector.to_list returns a sorted list, biggest matches first. *)
      module type Collector = sig
        type t
        val empty : t
        val union : t -> t -> t
        val inter : t -> t -> data list
        val to_list : t -> data list
      end
      module Collector : Collector
      val retrieve_generalizations_sorted : t -> input -> Collector.t
      val retrieve_unifiables_sorted : t -> input -> Collector.t
    end


module Make (I : Indexable) (A : Set.S) : DiscriminationTree 
with type constant_name = I.constant_name and type input = I.input
and type data = A.elt and type dataset = A.t