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diff --git a/components/tactics/negationTactics.ml b/components/tactics/negationTactics.ml
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+(* Copyright (C) 2002, 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://cs.unibo.it/helm/.
+ *)
+
+(* $Id$ *)
+
+let absurd_tac ~term =
+ let absurd_tac ~term status =
+  let (proof, goal) = status in
+  let module C = Cic in
+  let module U = UriManager in
+  let module P = PrimitiveTactics in
+  let _,metasenv,_subst,_,_, _ = 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 (absurd_URI, [] )) ; 
+	           term ; ty])
+      ) 
+      status
+    else raise (ProofEngineTypes.Fail (lazy "Absurd: Not a Proposition"))
+ in
+   ProofEngineTypes.mk_tactic (absurd_tac ~term)
+;;
+
+(* FG: METTERE I NOMI ANCHE QUI? CSC: in teoria si', per la intros*)
+let contradiction_tac =
+ let contradiction_tac status =
+  let module C = Cic in
+  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_
+      ~start:(P.intros_tac ())
+      ~continuation:(
+	 T.then_
+           ~start:
+             (EliminationTactics.elim_type_tac (C.MutInd (false_URI, 0, [])))
+           ~continuation: VariousTactics.assumption_tac))
+    status
+   with 
+    ProofEngineTypes.Fail msg when Lazy.force msg = "Assumption: No such assumption" -> raise (ProofEngineTypes.Fail (lazy "Contradiction: No such assumption"))
+    (* sarebbe piu' elegante se Assumtion sollevasse un'eccezione tutta sua che questa cattura, magari con l'aiuto di try_tactics *)
+ in 
+  ProofEngineTypes.mk_tactic contradiction_tac
+;;
+
+(* Questa era in fourierR.ml
+(* !!!!! fix !!!!!!!!!! *)
+let contradiction_tac (proof,goal)=
+        Tacticals.then_
+                ~start:(PrimitiveTactics.intros_tac ~name:"bo?" ) (*inutile sia questo che quello prima  della chiamata*)
+                ~continuation:(Tacticals.then_
+                        ~start:(VariousTactics.elim_type_tac ~term:_False)
+                        ~continuation:(assumption_tac))
+        (proof,goal)
+;;
+*)
+
+