--- /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/notation/relations/lazypredsnstar_7.ma".
+include "basic_2/reduction/llpx.ma".
+
+(* LAZY SN EXTENDED PARALLEL COMPUTATION ON LOCAL ENVIRONMENTS **************)
+
+definition llpxs: ∀h. sd h → genv → relation4 ynat term lenv lenv ≝
+ λh,g,G,d. LTC … (llpx h g G d).
+
+interpretation "lazy extended parallel computation (local environment, sn variant)"
+ 'LazyPRedSnStar G L1 L2 h g T d = (llpxs h g G d T L1 L2).
+
+(* Basic eliminators ********************************************************)
+
+lemma llpxs_ind: ∀h,g,G,L1,T,d. ∀R:predicate lenv. R L1 →
+ (∀L,L2. ⦃G, L1⦄ ⊢ ➡*[h, g, T, d] L → ⦃G, L⦄ ⊢ ➡[h, g, T, d] L2 → R L → R L2) →
+ ∀L2. ⦃G, L1⦄ ⊢ ➡*[h, g, T, d] L2 → R L2.
+#h #g #G #L1 #T #d #R #HL1 #IHL1 #L2 #HL12
+@(TC_star_ind … HL1 IHL1 … HL12) //
+qed-.
+
+lemma llpxs_ind_dx: ∀h,g,G,L2,T,d. ∀R:predicate lenv. R L2 →
+ (∀L1,L. ⦃G, L1⦄ ⊢ ➡[h, g, T, d] L → ⦃G, L⦄ ⊢ ➡*[h, g, T, d] L2 → R L → R L1) →
+ ∀L1. ⦃G, L1⦄ ⊢ ➡*[h, g, T, d] L2 → R L1.
+#h #g #G #L2 #T #d #R #HL2 #IHL2 #L1 #HL12
+@(TC_star_ind_dx … HL2 IHL2 … HL12) //
+qed-.
+
+(* Basic properties *********************************************************)
+
+lemma llpx_llpxs: ∀h,g,G,L1,L2,T,d. ⦃G, L1⦄ ⊢ ➡[h, g, T, d] L2 → ⦃G, L1⦄ ⊢ ➡*[h, g, T, d] L2.
+normalize /2 width=1 by inj/ qed.
+
+lemma llpxs_refl: ∀h,g,G,L,T,d. ⦃G, L⦄ ⊢ ➡*[h, g, T, d] L.
+/2 width=1 by llpx_llpxs/ qed.
+
+lemma llpxs_strap1: ∀h,g,G,L1,L,L2,T,d. ⦃G, L1⦄ ⊢ ➡*[h, g, T, d] L → ⦃G, L⦄ ⊢ ➡[h, g, T, d] L2 → ⦃G, L1⦄ ⊢ ➡*[h, g, T, d] L2.
+normalize /2 width=3 by step/ qed.
+
+lemma llpxs_strap2: ∀h,g,G,L1,L,L2,T,d. ⦃G, L1⦄ ⊢ ➡[h, g, T, d] L → ⦃G, L⦄ ⊢ ➡*[h, g, T, d] L2 → ⦃G, L1⦄ ⊢ ➡*[h, g, T, d] L2.
+normalize /2 width=3 by TC_strap/ qed.
+
+(* Basic forward lemmas *****************************************************)
+
+lemma llpxs_fwd_length: ∀h,g,G,L1,L2,T,d. ⦃G, L1⦄ ⊢ ➡*[h, g, T, d] L2 → |L1| = |L2|.
+#h #g #G #L1 #L2 #T #d #H @(llpxs_ind … H) -L2
+/3 width=8 by llpx_fwd_length, trans_eq/
+qed-.
+
+(* Note: this might be moved *)
+lemma llpxs_fwd_bind_sn: ∀h,g,a,I,G,L1,L2,V,T,d. ⦃G, L1⦄ ⊢ ➡*[h, g, ⓑ{a,I}V.T, d] L2 →
+ ⦃G, L1⦄ ⊢ ➡*[h, g, V, d] L2.
+#h #g #a #I #G #L1 #L2 #V #T #d #H @(llpxs_ind … H) -L2
+/3 width=6 by llpx_fwd_bind_sn, llpxs_strap1/
+qed-.
+
+(* Note: this might be moved *)
+lemma llpxs_fwd_bind_dx: ∀h,g,a,I,G,L1,L2,V,T,d. ⦃G, L1⦄ ⊢ ➡*[h, g, ⓑ{a,I}V.T, d] L2 →
+ ⦃G, L1.ⓑ{I}V⦄ ⊢ ➡*[h, g, T, ⫯d] L2.ⓑ{I}V.
+#h #g #a #I #G #L1 #L2 #V #T #d #H @(llpxs_ind … H) -L2
+/3 width=6 by llpx_fwd_bind_dx, llpxs_strap1/
+qed-.
+
+(* Note: this might be moved *)
+lemma llpxs_fwd_flat_sn: ∀h,g,I,G,L1,L2,V,T,d. ⦃G, L1⦄ ⊢ ➡*[h, g, ⓕ{I}V.T, d] L2 →
+ ⦃G, L1⦄ ⊢ ➡*[h, g, V, d] L2.
+#h #g #I #G #L1 #L2 #V #T #d #H @(llpxs_ind … H) -L2
+/3 width=6 by llpx_fwd_flat_sn, llpxs_strap1/
+qed-.
+
+(* Note: this might be moved *)
+lemma llpxs_fwd_flat_dx: ∀h,g,I,G,L1,L2,V,T,d. ⦃G, L1⦄ ⊢ ➡*[h, g, ⓕ{I}V.T, d] L2 →
+ ⦃G, L1⦄ ⊢ ➡*[h, g, T, d] L2.
+#h #g #I #G #L1 #L2 #V #T #d #H @(llpxs_ind … H) -L2
+/3 width=6 by llpx_fwd_flat_dx, llpxs_strap1/
+qed-.