update in lambdadelta

[helm.git] / matita / matita / contribs / lambdadelta / basic_2A / multiple / lleq_lleq.ma

diff --git a/matita/matita/contribs/lambdadelta/basic_2A/multiple/lleq_lleq.ma b/matita/matita/contribs/lambdadelta/basic_2A/multiple/lleq_lleq.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_2A/multiple/lleq_drop.ma".
+
+(* LAZY EQUIVALENCE FOR LOCAL ENVIRONMENTS **********************************)
+
+(* Main properties **********************************************************)
+
+theorem lleq_trans: ∀l,T. Transitive … (lleq l T).
+/2 width=3 by lleq_llpx_sn_trans/ qed-.
+
+theorem lleq_canc_sn: ∀L,L1,L2,T,l. L ≡[l, T] L1→ L ≡[l, T] L2 → L1 ≡[l, T] L2.
+/3 width=3 by lleq_trans, lleq_sym/ qed-.
+
+theorem lleq_canc_dx: ∀L1,L2,L,T,l. L1 ≡[l, T] L → L2 ≡[l, T] L → L1 ≡[l, T] L2.
+/3 width=3 by lleq_trans, lleq_sym/ qed-.
+
+(* Advanced properies on negated lazy equivalence *****************************)
+
+(* Note: for use in auto, works with /4 width=8/ so lleq_canc_sn is preferred *) 
+lemma lleq_nlleq_trans: ∀l,T,L1,L. L1 ≡[T, l] L →
+                        ∀L2. (L ≡[T, l] L2 → ⊥) → (L1 ≡[T, l] L2 → ⊥).
+/3 width=3 by lleq_canc_sn/ qed-.
+
+lemma nlleq_lleq_div: ∀l,T,L2,L. L2 ≡[T, l] L →
+                      ∀L1. (L1 ≡[T, l] L → ⊥) → (L1 ≡[T, l] L2 → ⊥).
+/3 width=3 by lleq_trans/ qed-.