1 (**************************************************************************)
4 (* ||A|| A project by Andrea Asperti *)
6 (* ||I|| Developers: *)
7 (* ||T|| The HELM team. *)
8 (* ||A|| http://helm.cs.unibo.it *)
10 (* \ / This file is distributed under the terms of the *)
11 (* v GNU General Public License Version 2 *)
13 (**************************************************************************)
15 include "static_2/syntax/sh_nexts.ma".
17 (* SORT HIERARCHY ***********************************************************)
19 (* acyclicity condition *)
20 record sh_acyclic (h): Prop ≝
22 (**) (* use extensional equivalence *)
23 sh_nexts_inj: ∀s,n1,n2. ⇡*[h,n1]s = ⇡*[h,n2]s → n1 = n2
26 (* decidability condition *)
27 record sh_decidable (h): Prop ≝
29 sh_nexts_dec: ∀s1,s2. Decidable (∃n. ⇡*[h,n]s1 = s2)