--- /dev/null
+(* Copyright (C) 2006, 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/
+ *)
+
+type 'a t = ('a, int ref) Hashtbl.t
+
+let create () = Hashtbl.create 113
+
+let incr ~create_cb counters item =
+ try
+ let counter = Hashtbl.find counters item in
+ incr counter
+ with Not_found ->
+ Hashtbl.add counters item (ref 1);
+ create_cb item
+
+let decr ~delete_cb counters item =
+ try
+ let counter = Hashtbl.find counters item in
+ decr counter;
+ if !counter = 0 then begin
+ Hashtbl.remove counters item;
+ delete_cb item
+ end
+ with Not_found ->
+ prerr_endline "RefCounter: attempt to decrease unexistent counter";
+ assert false
+
--- /dev/null
+(* Copyright (C) 2006, 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/
+ *)
+
+type 'a t
+
+val create: unit -> 'a t
+val incr: create_cb:('a -> unit) -> 'a t -> 'a -> unit
+val decr: delete_cb:('a -> unit) -> 'a t -> 'a -> unit
+