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diff --git a/helm/ocaml/library/coercDb.ml b/helm/ocaml/library/coercDb.ml
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+++ b/helm/ocaml/library/coercDb.ml
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+(* 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/
+ *)
+
+(* $Id$ *)
+
+type coerc_carr = Uri of UriManager.uri | Sort of Cic.sort | Term of Cic.term
+exception EqCarrNotImplemented of string Lazy.t
+exception EqCarrOnNonMetaClosed
+
+let db = ref []
+
+let coerc_carr_of_term t =
+  try
+    Uri (CicUtil.uri_of_term t)
+  with Invalid_argument _ ->
+    match t with
+    | Cic.Sort s -> Sort s
+    | t -> Term t
+;;
+
+let eq_carr src tgt =
+  match src, tgt with
+  | Uri src, Uri tgt -> UriManager.eq src tgt
+  | Sort (Cic.Type _), Sort (Cic.Type _) -> true
+  | Sort src, Sort tgt when src = tgt -> true
+  | Term t1, Term t2 ->
+    if CicUtil.is_meta_closed t1 && CicUtil.is_meta_closed t2 then
+      raise 
+        (EqCarrNotImplemented 
+          (lazy ("Unsupported carr for coercions: " ^ 
+            CicPp.ppterm t1 ^ " or " ^ CicPp.ppterm t2)))
+    else raise EqCarrOnNonMetaClosed
+  | _, _ -> false
+
+let name_of_carr = function
+  | Uri u -> UriManager.name_of_uri u
+  | Sort s -> CicPp.ppsort s
+  | Term t -> CicPp.ppterm t
+  
+
+let to_list () =
+  !db
+
+let add_coercion c =
+  db := c :: !db
+
+let remove_coercion p = 
+  db := List.filter (fun u -> not(p u)) !db
+
+let find_coercion f =
+  List.map (fun (_,_,x) -> x) (List.filter (fun (s,t,_) -> f (s,t)) !db)
+
+let is_a_coercion u =
+  List.exists (fun (_,_,x) -> UriManager.eq x u) !db
+
+let get_carr uri =
+  try
+    let src, tgt, _ = List.find (fun (_,_,x) -> UriManager.eq x uri) !db in
+    src, tgt
+  with Not_found -> assert false (* uri must be a coercion *)
+
+let term_of_carr = function
+  | Uri u -> CicUtil.term_of_uri u
+  | Sort s -> Cic.Sort s
+  | Term _ -> assert false
+  
+
+