matita/matita/contribs/lambdadelta/static_2/syntax/bind.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 "static_2/syntax/term.ma".
  16
  17 (* BINDERS FOR LOCAL ENVIRONMENTS ******************************************)
  18
  19 inductive bind: Type[0] ≝
  20 | BUnit: bind1 → bind
  21 | BPair: bind2 → term → bind
  22 .
  23
  24 (* Basic properties ********************************************************)
  25
  26 lemma eq_bind_dec: ∀I1,I2:bind. Decidable (I1 = I2).
  27 * #I1 [2: #V1 ] * #I2 [2,4: #V2 ]
  28 [1: elim (eq_bind2_dec I1 I2) #HI
  29     [ elim (eq_term_dec V1 V2) #HV ]
  30 |4: elim (eq_bind1_dec I1 I2) #HI
  31 ]
  32 /2 width=1 by or_introl/
  33 @or_intror #H destruct /2 width=1 by/
  34 qed-.