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:                                           *)
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  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).