update in basic_2

[helm.git] / matita / matita / contribs / lambdadelta / basic_2 / syntax / genv_weight.ma

diff --git a/matita/matita/contribs/lambdadelta/basic_2/syntax/genv_weight.ma b/matita/matita/contribs/lambdadelta/basic_2/syntax/genv_weight.ma
new file mode 100644 (file)
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+++ b/matita/matita/contribs/lambdadelta/basic_2/syntax/genv_weight.ma
@@ -0,0 +1,30 @@
+(**************************************************************************)
+(*       ___                                                              *)
+(*      ||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/syntax/term_weight.ma".
+include "basic_2/syntax/genv.ma".
+
+(* WEIGHT OF A GLOBAL ENVIRONMENT *******************************************)
+
+rec definition gw G ≝ match G with
+[ GAtom       ⇒ 0
+| GPair G I T ⇒ gw G + ♯{T}
+].
+
+interpretation "weight (global environment)" 'Weight G = (gw G).
+
+(* Basic properties *********************************************************)
+
+lemma gw_pair: ∀I,G,T. ♯{G} < ♯{G.ⓑ{I}T}.
+normalize /2 width=1 by monotonic_le_plus_r/ qed.