- degree-based equivalene for terms

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

diff --git a/matita/matita/contribs/lambdadelta/basic_2/syntax/term_weight.ma b/matita/matita/contribs/lambdadelta/basic_2/syntax/term_weight.ma
new file mode 100644 (file)
index 0000000..9076a9b
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+++ b/matita/matita/contribs/lambdadelta/basic_2/syntax/term_weight.ma
@@ -0,0 +1,38 @@
+(**************************************************************************)
+(*       ___                                                              *)
+(*      ||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/notation/functions/weight_1.ma".
+include "basic_2/syntax/term.ma".
+
+(* WEIGHT OF A TERM *********************************************************)
+
+rec definition tw T ≝ match T with
+[ TAtom _     ⇒ 1
+| TPair _ V T ⇒ tw V + tw T + 1
+].
+
+interpretation "weight (term)" 'Weight T = (tw T).
+
+(* Basic properties *********************************************************)
+
+(* Basic_1: was: tweight_lt *)
+lemma tw_pos: ∀T. 1 ≤ ♯{T}.
+#T elim T -T //
+qed.
+
+(* Basic_1: removed theorems 11:
+            wadd_le wadd_lt wadd_O weight_le weight_eq weight_add_O
+            weight_add_S tlt_trans tlt_head_sx tlt_head_dx tlt_wf_ind
+*)
+(* Basic_1: removed local theorems 1: q_ind *)