X-Git-Url: http://matita.cs.unibo.it/gitweb/?a=blobdiff_plain;f=matita%2Fmatita%2Fcontribs%2Flambdadelta%2Fbasic_2%2Fdynamic%2Fcnv_drops.ma;h=8c95ffcf6db0a002ee1878780d11743528c1c8a8;hb=dd93a0919b67bead0d4f07d49dfc198006edc9aa;hp=c979465c31d3ce4d730f2c36967a96cb7009e057;hpb=b634a816745cf8a9a7ad14650d088232c8ee1a1a;p=helm.git

diff --git a/matita/matita/contribs/lambdadelta/basic_2/dynamic/cnv_drops.ma b/matita/matita/contribs/lambdadelta/basic_2/dynamic/cnv_drops.ma
index c979465c3..8c95ffcf6 100644
--- a/matita/matita/contribs/lambdadelta/basic_2/dynamic/cnv_drops.ma
+++ b/matita/matita/contribs/lambdadelta/basic_2/dynamic/cnv_drops.ma
@@ -15,13 +15,13 @@
 include "basic_2/rt_computation/cpms_drops.ma".
 include "basic_2/dynamic/cnv.ma".
 
-(* CONTEXT_SENSITIVE NATIVE VALIDITY FOR TERMS ******************************)
+(* CONTEXT-SENSITIVE NATIVE VALIDITY FOR TERMS ******************************)
 
 (* Advanced dproperties *****************************************************)
 
 (* Basic_2A1: uses: snv_lref *)
 lemma cnv_lref_drops (a) (h) (G): ∀I,K,V,i,L. ⦃G, K⦄ ⊢ V ![a, h] →
-                                  ⬇*[i] L ≘ K.ⓑ{I}V →  ⦃G, L⦄ ⊢ #i ![a, h].
+                                  ⬇*[i] L ≘ K.ⓑ{I}V → ⦃G, L⦄ ⊢ #i ![a, h].
 #a #h #G #I #K #V #i elim i -i
 [ #L #HV #H
   lapply (drops_fwd_isid … H ?) -H // #H destruct
@@ -49,6 +49,16 @@ lemma cnv_inv_lref_drops (a) (h) (G):
 ]
 qed-.
 
+(* Advanced forward lemmas **************************************************)
+
+lemma cnv_lref_fwd_drops (a) (h) (G):
+                         ∀i,L. ⦃G, L⦄ ⊢ #i ![a, h] →
+                         ∀I,K,V. ⬇*[i] L ≘ K.ⓑ{I}V → ⦃G, K⦄ ⊢ V ![a, h].
+#a #h #o #i #L #H #I #K #V #HLK
+elim (cnv_inv_lref_drops … H) -H #Z #Y #X #HLY #HX
+lapply (drops_mono … HLY … HLK) -L #H destruct //
+qed-.   
+
 (* Properties with generic slicing for local environments *******************)
 
 (* Basic_2A1: uses: snv_lift *)