matita/matita/contribs/lambdadelta/static_2/syntax/sh_props.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 "static_2/syntax/sh.ma".
  16
  17 (* SORT HIERARCHY ***********************************************************)
  18
  19 (* acyclicity condition *)
  20 record sh_acyclic (h): Prop ≝
  21 {
  22   nexts_inj: ∀s,n1,n2. (next h)^n1 s = (next h)^n2 s → n1 = n2
  23 }.
  24
  25 (* decidability condition *)
  26 record sh_decidable (h): Prop ≝
  27 {
  28   nexts_dec: ∀s1,s2. Decidable (∃n. (next h)^n s1 = s2)
  29 }.