update in ground

[helm.git] / matita / matita / contribs / lambdadelta / ground / lib / subset_ext_equivalence.ma

diff --git a/matita/matita/contribs/lambdadelta/ground/lib/subset_ext_equivalence.ma b/matita/matita/contribs/lambdadelta/ground/lib/subset_ext_equivalence.ma
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+(**************************************************************************)
+(*       ___                                                              *)
+(*      ||M||                                                             *)
+(*      ||A||       A project by Andrea Asperti                           *)
+(*      ||T||                                                             *)
+(*      ||I||       Developers:                                           *)
+(*      ||T||         The HELM team.                                      *)
+(*      ||A||         http://helm.cs.unibo.it                             *)
+(*      \   /                                                             *)
+(*       \ /        This file is distributed under the terms of the       *)
+(*        v         GNU General Public License Version 2                  *)
+(*                                                                        *)
+(**************************************************************************)
+
+include "ground/lib/subset_ext_inclusion.ma".
+include "ground/lib/subset_equivalence.ma".
+
+(* EXTENSIONS FOR SUBSETS ***************************************************)
+
+(* Constructions with subset_equivalence ************************************)
+
+lemma subset_equivalence_ext_f1_bi (A1) (A0) (f) (u1) (v1):
+      u1 ⇔ v1 → subset_ext_f1 A1 A0 f u1 ⇔ subset_ext_f1 A1 A0 f v1.
+#A1 #A0 #f #u1 #v1 * #Huv1 #Hvu1
+/3 width=3 by subset_inclusion_ext_f1_bi, conj/
+qed.