matita/matita/contribs/lambdadelta/basic_2/syntax/bind_weight.ma

   1 (**************************************************************************)
   2 (*       ___                                                              *)
   3 (*      ||M||                                                             *)
   4 (*      ||A||       A project by Andrea Asperti                           *)
   5 (*      ||T||                                                             *)
   6 (*      ||I||       Developers:                                           *)
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   9 (*      \   /                                                             *)
  10 (*       \ /        This file is distributed under the terms of the       *)
  11 (*        v         GNU General Public License Version 2                  *)
  12 (*                                                                        *)
  13 (**************************************************************************)
  14
  15 include "basic_2/syntax/term.ma".
  16
  17 (* BINDERS FOR LOCAL ENVIRONMENTS ******************************************)
  18
  19 include "basic_2/syntax/term_weight.ma".
  20 include "basic_2/syntax/bind.ma".
  21
  22 (* WEIGHT OF A BINDER FOR LOCAL ENVIRONMENTS *******************************)
  23
  24 rec definition bw I ≝ match I with
  25 [ BUnit _   ⇒ 1
  26 | BPair _ V ⇒ ♯{V}
  27 ].
  28
  29 interpretation "weight (binder for local environments)" 'Weight I = (bw I).
  30
  31 (* Basic properties *********************************************************)
  32
  33 lemma bw_pos: ∀I. 1 ≤ ♯{I}.
  34 * //
  35 qed.