- degree-based equivalene for terms

[helm.git] / matita / matita / contribs / lambdadelta / alpha_1 / syntax / term_append.ma

diff --git a/matita/matita/contribs/lambdadelta/alpha_1/syntax/term_append.ma b/matita/matita/contribs/lambdadelta/alpha_1/syntax/term_append.ma
new file mode 100644 (file)
index 0000000..4ea795a
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+++ b/matita/matita/contribs/lambdadelta/alpha_1/syntax/term_append.ma
@@ -0,0 +1,25 @@
+(**************************************************************************)
+(*       ___                                                              *)
+(*      ||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 "alpha_1/syntax/term.ma".
+
+(* TERMS ********************************************************************)
+
+let rec tappend T U on T ≝ match T with
+[ TAtom       ⇒ U
+| TUnit I T   ⇒ ①{I}.(tappend T U)
+| TPair I V T ⇒ ②{I}V.(tappend T U)
+].
+
+interpretation "append (term)" 'Append T U = (tappend T U).