updating the structures for sorts

[helm.git] / matita / matita / contribs / lambdadelta / static_2 / syntax / sh_props.ma

diff --git a/matita/matita/contribs/lambdadelta/static_2/syntax/sh_props.ma b/matita/matita/contribs/lambdadelta/static_2/syntax/sh_props.ma
new file mode 100644 (file)
index 0000000..4302026
--- /dev/null
+++ b/matita/matita/contribs/lambdadelta/static_2/syntax/sh_props.ma
@@ -0,0 +1,29 @@
+(**************************************************************************)
+(*       ___                                                              *)
+(*      ||M||                                                             *)
+(*      ||A||       A project by Andrea Asperti                           *)
+(*      ||T||                                                             *)
+(*      ||I||       Developers:                                           *)
+(*      ||T||         The HELM team.                                      *)
+(*      ||A||         http://helm.cs.unibo.it                             *)
+(*      \   /                                                             *)
+(*       \ /        This file is distributed under the terms of the       *)
+(*        v         GNU General Public License Version 2                  *)
+(*                                                                        *)
+(**************************************************************************)
+
+include "static_2/syntax/sh.ma".
+
+(* SORT HIERARCHY ***********************************************************)
+
+(* acyclicity condition *)
+record sh_acyclic (h): Prop ≝
+{
+  nexts_inj: ∀s,n1,n2. (next h)^n1 s = (next h)^n2 s → n1 = n2
+}.
+
+(* decidability condition *)
+record sh_decidable (h): Prop ≝
+{
+  nexts_dec: ∀s1,s2. Decidable (∃n. (next h)^n s1 = s2)
+}.