X-Git-Url: http://matita.cs.unibo.it/gitweb/?a=blobdiff_plain;f=matita%2Fmatita%2Fcontribs%2Flambdadelta%2Fbasic_2%2Fmultiple%2Fllor_ldrop.ma;h=f247442917f0a76e15a187fd94cbd78d7881926e;hb=a2092f7ba4c7c566ea90653ff57e4623ab94d8d5;hp=b766269e7ded295a859dd85500d3f722224ae256;hpb=4aa343ba8e1c807108203ece4e142c81b27d28e8;p=helm.git

diff --git a/matita/matita/contribs/lambdadelta/basic_2/multiple/llor_ldrop.ma b/matita/matita/contribs/lambdadelta/basic_2/multiple/llor_ldrop.ma
index b766269e7..f24744291 100644
--- a/matita/matita/contribs/lambdadelta/basic_2/multiple/llor_ldrop.ma
+++ b/matita/matita/contribs/lambdadelta/basic_2/multiple/llor_ldrop.ma
@@ -19,4 +19,12 @@ include "basic_2/multiple/llor.ma".
 
 (* Advanced properties ******************************************************)
 
+lemma llor_skip: ∀L1,L2,U,d. |L1| ≤ |L2| → yinj (|L1|) ≤ d → L1 ⩖[U, d] L2 ≡ L1.
+#L1 #L2 #U #d #HL12 #Hd @and3_intro // -HL12
+#I1 #I2 #I #K1 #K2 #K #W1 #W2 #W #i #HLK1 #_ #HLK -I2 -L2 -K2
+lapply (ldrop_mono … HLK … HLK1) -HLK #H destruct
+lapply (ldrop_fwd_length_lt2 … HLK1) -K1
+/5 width=3 by ylt_yle_trans, ylt_inj, or3_intro0, and3_intro/
+qed.
+
 axiom llor_total: ∀L1,L2,T,d. |L1| ≤ |L2| → ∃L. L1 ⩖[T, d] L2 ≡ L.