update in static_2

[helm.git] / matita / matita / contribs / lambdadelta / static_2 / syntax / teq_ext_teq_ext.ma

diff --git a/matita/matita/contribs/lambdadelta/static_2/syntax/teq_ext_teq_ext.ma b/matita/matita/contribs/lambdadelta/static_2/syntax/teq_ext_teq_ext.ma
new file mode 100644 (file)
index 0000000..c3282d5
--- /dev/null
+++ b/matita/matita/contribs/lambdadelta/static_2/syntax/teq_ext_teq_ext.ma
@@ -0,0 +1,28 @@
+(**************************************************************************)
+(*       ___                                                              *)
+(*      ||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 "static_2/syntax/teq_teq.ma".
+include "static_2/syntax/teq_ext.ma".
+
+(* SYNTACTIC EQUIVALENCE ****************************************************)
+
+(* Main properties **********************************************************)
+
+theorem ceq_ext_trans (I):
+        ∀L1,I1. L1 ⊢ I1 ≡ I → ∀L2,I2. L2 ⊢ I ≡ I2 → ∀L3. L3 ⊢ I1 ≡ I2.
+#I #L1 #I1 * -I1 -I //
+#I1 #V1 #V #HV1 #L2 #Z #H
+elim (ext2_inv_pair_sn … H) -H #V2 #HV2 #H #L3 destruct
+/3 width=3 by ext2_pair, teq_trans/
+qed-.