- some refactoring

[helm.git] / matita / matita / contribs / lambda-delta / Basic-2 / grammar / lenv_length.ma

diff --git a/matita/matita/contribs/lambda-delta/Basic-2/grammar/lenv_length.ma b/matita/matita/contribs/lambda-delta/Basic-2/grammar/lenv_length.ma
new file mode 100644 (file)
index 0000000..437730a
--- /dev/null
+++ b/matita/matita/contribs/lambda-delta/Basic-2/grammar/lenv_length.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 "Basic-2/grammar/lenv.ma".
+
+(* LENGTH *******************************************************************)
+
+(* the length of a local environment *)
+let rec length L ≝ match L with
+[ LSort       ⇒ 0
+| LPair L _ _ ⇒ length L + 1
+].
+
+interpretation "length (local environment)" 'card L = (length L).