X-Git-Url: http://matita.cs.unibo.it/gitweb/?a=blobdiff_plain;f=helm%2Fsoftware%2Fcomponents%2Ftactics%2FnegationTactics.ml;h=c973d75f4706d20754266f4c8df2facd686b9ebe;hb=08a92d276c5477968b02f31097b6ed03185f34eb;hp=7ee79e534aa1907cea1beca63580b55a9dc42836;hpb=9efaf66294d18446b7cd960f9ed4203799073e62;p=helm.git

diff --git a/helm/software/components/tactics/negationTactics.ml b/helm/software/components/tactics/negationTactics.ml
index 7ee79e534..c973d75f4 100644
--- a/helm/software/components/tactics/negationTactics.ml
+++ b/helm/software/components/tactics/negationTactics.ml
@@ -33,13 +33,18 @@ let absurd_tac ~term =
   let module P = PrimitiveTactics in
   let _,metasenv,_,_ = proof in
   let _,context,ty = CicUtil.lookup_meta goal metasenv in
+  let absurd_URI =
+   match LibraryObjects.absurd_URI () with
+      Some uri -> uri
+    | None -> raise (ProofEngineTypes.Fail (lazy "You need to register the default \"absurd\" theorem first. Please use the \"default\" command"))
+  in
   let ty_term,_ = 
     CicTypeChecker.type_of_aux' metasenv context term CicUniv.empty_ugraph in
     if (ty_term = (C.Sort C.Prop)) (* ma questo controllo serve?? *)
     then ProofEngineTypes.apply_tactic 
       (P.apply_tac 
          ~term:(
-           C.Appl [(C.Const (LibraryObjects.absurd_URI (), [] )) ; 
+           C.Appl [(C.Const (absurd_URI, [] )) ; 
 	           term ; ty])
       ) 
       status
@@ -55,6 +60,11 @@ let contradiction_tac =
   let module U = UriManager in
   let module P = PrimitiveTactics in
   let module T = Tacticals in
+  let false_URI =
+   match LibraryObjects.false_URI () with
+      Some uri -> uri
+    | None -> raise (ProofEngineTypes.Fail (lazy "You need to register the default \"false\" definition first. Please use the \"default\" command"))
+  in
    try
     ProofEngineTypes.apply_tactic (
      T.then_
@@ -62,8 +72,7 @@ let contradiction_tac =
       ~continuation:(
 	 T.then_
            ~start:
-             (EliminationTactics.elim_type_tac 
-                (C.MutInd (LibraryObjects.false_URI (), 0, [])))
+             (EliminationTactics.elim_type_tac (C.MutInd (false_URI, 0, [])))
            ~continuation: VariousTactics.assumption_tac))
     status
    with