--- /dev/null
+(**************************************************************************)
+(* ___ *)
+(* ||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 "basic_2/computation/xprs_cprs.ma".
+include "basic_2/computation/yprs.ma".
+
+(* HYPER PARALLEL COMPUTATION ON CLOSURES ***********************************)
+
+(* Properties on extended parallel computation for terms ********************)
+
+lemma xprs_yprs: ∀h,g,L,T1,T2. ⦃h, L⦄ ⊢ T1 •➡*[g] T2 →
+ h ⊢ ⦃L, T1⦄ •⥸*[g] ⦃L, T2⦄.
+#h #g #L #T1 #T2 #H @(xprs_ind … H) -T2 // /3 width=4/
+qed.
+
+lemma cprs_yprs: ∀h,g,L,T1,T2. L ⊢ T1 ➡* T2 → h ⊢ ⦃L, T1⦄ •⥸*[g] ⦃L, T2⦄.
+/3 width=1/ qed.