matita/matita/contribs/lambda-delta/Basic-2/grammar/lenv_length.ma

   1 (**************************************************************************)
   2 (*       ___                                                              *)
   3 (*      ||M||                                                             *)
   4 (*      ||A||       A project by Andrea Asperti                           *)
   5 (*      ||T||                                                             *)
   6 (*      ||I||       Developers:                                           *)
   7 (*      ||T||         The HELM team.                                      *)
   8 (*      ||A||         http://helm.cs.unibo.it                             *)
   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/grammar/lenv.ma".
  16
  17 (* LENGTH OF A LOCAL ENVIRONMENT ********************************************)
  18
  19 let rec length L ≝ match L with
  20 [ LAtom       ⇒ 0
  21 | LPair L _ _ ⇒ length L + 1
  22 ].
  23
  24 interpretation "length (local environment)" 'card L = (length L).