+(**************************************************************************)
+(* ___ *)
+(* ||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 *)
+(* *)
+(**************************************************************************)
+
+notation "hvbox( h ⊢ break ⦃ L1, break T1 ⦄ • ⥸ break [ g ] break ⦃ L2 , break T2 ⦄ )"
+ non associative with precedence 45
+ for @{ 'YPRed $h $g $L1 $T1 $L2 $T2 }.
+
+include "basic_2/substitution/csup.ma".
+include "basic_2/reducibility/xpr.ma".
+
+(* HYPER PARALLEL REDUCTION ON CLOSURES *************************************)
+
+inductive ypr (h) (g) (L1) (T1): relation2 lenv term ≝
+| ypr_cpr : ∀T2. L1 ⊢ T1 ➡ T2 → ypr h g L1 T1 L1 T2
+| ypr_ssta: ∀T2,l. ⦃h, L1⦄ ⊢ T1 •[g, l + 1] T2 → ypr h g L1 T1 L1 T2
+| ypr_csup: ∀L2,T2. ⦃L1, T1⦄ > ⦃L2, T2⦄ → ypr h g L1 T1 L2 T2
+.
+
+interpretation
+ "hyper parallel reduction (closure)"
+ 'YPRed h g L1 T1 L2 T2 = (ypr h g L1 T1 L2 T2).
+
+(* Basic properties *********************************************************)
+
+lemma ypr_refl: ∀h,g. bi_reflexive … (ypr h g).
+/2 width=1/ qed.
+
+lemma xpr_ypr: ∀h,g,L,T1,T2. ⦃h, L⦄ ⊢ T1 •➡[g] T2 → h ⊢ ⦃L, T1⦄ •⥸[g] ⦃L, T2⦄.
+#h #g #L #T1 #T2 * /2 width=1/ /2 width=2/
+qed.