- parallel reduction for local environments: we proved the equivalence

[helm.git] / matita / matita / contribs / lambda_delta / basic_2 / computation / cprs_lfpr.ma

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+(**************************************************************************)
+(*       ___                                                              *)
+(*      ||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/reducibility/ltpr_tps.ma".
+include "basic_2/reducibility/cpr_ltpss.ma".
+include "basic_2/reducibility/lfpr.ma".
+include "basic_2/computation/cprs.ma".
+
+(* CONTEXT-SENSITIVE PARALLEL COMPUTATION ON TERMS **************************)
+
+(* Properties concerning focalized parallel reduction on local environments *)
+
+lemma ltpr_tpss_trans: ∀L1,L2. L1 ➡ L2 → ∀T1,T2,d,e. L2 ⊢ T1 ▶* [d, e] T2 →
+                       ∃∃T. L1 ⊢ T1 ▶* [d, e] T & L1 ⊢ T ➡* T2.
+#L1 #L2 #HL12 #T1 #T2 #d #e #H @(tpss_ind … H) -T2
+[ /2 width=3/
+| #T #T2 #_ #HT2 * #T0 #HT10 #HT0
+  elim (ltpr_tps_trans … HT2 … HL12) -L2 #T3 #HT3 #HT32
+  @(ex2_1_intro … HT10) -T1 (**) (* explicit constructors *)
+  @(cprs_strap1 … T3 …) /2 width=1/ -HT32
+  @(cprs_strap1 … HT0) -HT0 /3 width=3/
+]
+qed.
+
+(* Basic_1: was just: pr3_pr0_pr2_t *)
+lemma ltpr_cpr_trans: ∀L1,L2. L1 ➡ L2 → ∀T1,T2. L2 ⊢ T1 ➡ T2 → L1 ⊢ T1 ➡* T2.
+#L1 #L2 #HL12 #T1 #T2 * #T #HT1
+<(ltpr_fwd_length … HL12) #HT2
+elim (ltpr_tpss_trans … HL12 … HT2) -L2 /3 width=3/
+qed.
+
+(* Basic_1: was just: pr3_pr2_pr2_t *)
+lemma lfpr_cpr_trans: ∀L1,L2. ⦃L1⦄ ➡ ⦃L2⦄ → ∀T1,T2. L2 ⊢ T1 ➡ T2 → L1 ⊢ T1 ➡* T2.
+#L1 #L2 * /3 width=7/
+qed.