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+(************************************************************************)
+(*  v      *   The Coq Proof Assistant  /  The Coq Development Team     *)
+(* <O___,, * CNRS-Ecole Polytechnique-INRIA Futurs-Universite Paris Sud *)
+(*   \VV/  **************************************************************)
+(*    //   *      This file is distributed under the terms of the       *)
+(*         *       GNU Lesser General Public License Version 2.1        *)
+(************************************************************************)
+
+(* $Id: dn.ml,v 1.5.16.1 2004/07/16 19:30:52 herbelin Exp $ *)
+
+(* This file implements the basic structure of what Chet called
+   ``discrimination nets''. If my understanding is right, it serves
+   to associate actions (for example, tactics) with a priority to term
+   patterns, so that if a hypothesis matches a pattern in the net,
+   then the associated tactic is applied. Discrimination nets are used
+   (only) to implement the tactics Auto, DHyp and Point.
+
+   A discrimination net is a tries structure, that is, a tree structure 
+   specially conceived for searching patterns, like for example strings
+   --see the file Tlm.ml in the directory lib/util--. Here the tries
+   structure are used for looking for term patterns.
+
+   This module is then used in :
+     - termdn.ml   (discrimination nets of terms);
+     - btermdn.ml  (discrimination nets of terms with bounded depth,
+                    used in the tactic auto);
+     - nbtermdn.ml (named discrimination nets with bounded depth, used
+                    in the tactics Dhyp and Point).
+  Eduardo (4/8/97) *)
+
+(* Definition of the basic structure *)
+
+type ('lbl,'pat) decompose_fun = 'pat -> ('lbl * 'pat list) option
+
+type ('lbl,'pat,'inf) t = (('lbl * int) option,'pat * 'inf) Tlm.t
+
+let create () = Tlm.empty
+
+(* [path_of dna pat] returns the list of nodes of the pattern [pat] read in 
+prefix ordering, [dna] is the function returning the main node of a pattern *)
+
+let path_of dna =
+  let rec path_of_deferred = function
+    | [] -> []
+    | h::tl -> pathrec tl h
+	    
+  and pathrec deferred t =
+    match dna t with
+      | None -> 
+	  None :: (path_of_deferred deferred)
+      | Some (lbl,[]) ->
+	  (Some (lbl,0))::(path_of_deferred deferred)
+      | Some (lbl,(h::def_subl as v)) ->
+	  (Some (lbl,List.length v))::(pathrec (def_subl@deferred) h)
+  in 
+  pathrec []
+    
+let tm_of tm lbl =
+  try [Tlm.map tm lbl] with Not_found -> []
+
+let lookup tm dna t =
+  let rec lookrec t tm =
+    (tm_of tm None)@
+    (match dna t with
+       | None -> []
+       | Some(lbl,v) ->
+	   List.fold_left 
+	     (fun l c -> List.flatten(List.map (lookrec c) l))
+             (tm_of tm (Some(lbl,List.length v))) v)
+  in 
+  List.flatten(List.map Tlm.xtract (lookrec t tm))
+
+let add tm dna (pat,inf) =
+  let p = path_of dna pat in Tlm.add tm (p,(pat,inf))
+    
+let rmv tm dna (pat,inf) =
+  let p = path_of dna pat in Tlm.rmv tm (p,(pat,inf))
+    
+let app f tm = Tlm.app (fun (_,p) -> f p) tm
+