matita/matita/contribs/lambdadelta/basic_2/dynamic/nta_eval.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                  *)
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  13 (**************************************************************************)
  14
  15 include "basic_2/dynamic/cnv_eval.ma".
  16 include "basic_2/dynamic/nta_preserve.ma".
  17
  18 (* NATIVE TYPE ASSIGNMENT FOR TERMS *****************************************)
  19
  20 (* Properties with evaluations for rt-transition on terms *******************)
  21
  22 lemma nta_typecheck_dec (h) (a) (G) (L): ac_props a →
  23       ∀T,U. Decidable … (❪G,L❫ ⊢ T :[h,a] U).
  24 /2 width=1 by cnv_dec/ qed-.
  25
  26 (* Basic_1: uses: ty3_inference *)
  27 lemma nta_inference_dec (h) (a) (G) (L) (T): ac_props a →
  28       Decidable (∃U. ❪G,L❫ ⊢ T :[h,a] U).
  29 #h #a #G #L #T #Ha
  30 elim (cnv_dec h … G L T Ha) -Ha #HT
  31 [ /3 width=1 by cnv_nta_sn, or_introl/
  32 | @or_intror * #U #HTU
  33   /3 width=2 by nta_fwd_cnv_sn/
  34 ]
  35 qed-.