X-Git-Url: http://matita.cs.unibo.it/gitweb/?a=blobdiff_plain;f=helm%2Fsoftware%2Fcomponents%2Ftactics%2Finversion.ml;h=74117f7109dd596602e0d1ee26a23c7a1cd132da;hb=0a50912f2577243a1f9e4068b02877b8e61181c9;hp=f5e2a847690f2b4c20544c32d9a18ba25108177c;hpb=fc4cf455977934bd737c3d6c8675ef7663a6a588;p=helm.git

diff --git a/helm/software/components/tactics/inversion.ml b/helm/software/components/tactics/inversion.ml
index f5e2a8476..74117f710 100644
--- a/helm/software/components/tactics/inversion.ml
+++ b/helm/software/components/tactics/inversion.ml
@@ -171,6 +171,7 @@ let isSetType paramty = ((Pervasives.compare
   (get_sort_type paramty)
   (Cic.Sort Cic.Prop)) != 0) 
 
+exception EqualityNotDefinedYet
 let private_inversion_tac ~term =
  let module T = CicTypeChecker in
  let module R = CicReduction in
@@ -181,7 +182,11 @@ let private_inversion_tac ~term =
  
  (*DEBUG*) debug_print (lazy  ("private inversion begins"));
  let (_,metasenv,_,_) = proof in
- let uri_of_eq = LibraryObjects.eq_URI () in
+ let uri_of_eq =
+  match LibraryObjects.eq_URI () with
+     None -> raise EqualityNotDefinedYet
+  | Some uri -> uri
+ in
  let (_,context,goalty) = CicUtil.lookup_meta goal metasenv in
  let termty,_ = T.type_of_aux' metasenv context term CicUniv.empty_ugraph in
  let uri = baseuri_of_term termty in