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4 (* ||A|| A project by Andrea Asperti *)
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7 (* ||T|| The HELM team. *)
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15 include "basic_2/dynamic/cnv_eval.ma".
16 include "basic_2/dynamic/nta_preserve.ma".
18 (* NATIVE TYPE ASSIGNMENT FOR TERMS *****************************************)
20 (* Properties with evaluations for rt-transition on terms *******************)
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-.
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).
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/