X-Git-Url: http://matita.cs.unibo.it/gitweb/?a=blobdiff_plain;f=matita%2Fmatita%2Fcontribs%2Flambdadelta%2Fbasic_2%2Fsubstitution%2Fldrop.ma;h=c8b2b11f2d9fe16651eaf34dbd322c20588c32ed;hb=a2092f7ba4c7c566ea90653ff57e4623ab94d8d5;hp=97eab47d4c42cfaddb9f558176142031d510deab;hpb=4aa343ba8e1c807108203ece4e142c81b27d28e8;p=helm.git

diff --git a/matita/matita/contribs/lambdadelta/basic_2/substitution/ldrop.ma b/matita/matita/contribs/lambdadelta/basic_2/substitution/ldrop.ma
index 97eab47d4..c8b2b11f2 100644
--- a/matita/matita/contribs/lambdadelta/basic_2/substitution/ldrop.ma
+++ b/matita/matita/contribs/lambdadelta/basic_2/substitution/ldrop.ma
@@ -233,6 +233,10 @@ lemma ldrop_O1_ge: ∀L,e. |L| ≤ e → ⇩[Ⓣ, 0, e] L ≡ ⋆.
 normalize /4 width=1 by ldrop_drop, monotonic_pred/
 qed.
 
+lemma ldrop_O1_eq: ∀L,s. ⇩[s, 0, |L|] L ≡ ⋆.
+#L elim L -L /2 width=1 by ldrop_drop, ldrop_atom/
+qed.
+
 lemma ldrop_split: ∀L1,L2,d,e2,s. ⇩[s, d, e2] L1 ≡ L2 → ∀e1. e1 ≤ e2 →
                    ∃∃L. ⇩[s, d, e2 - e1] L1 ≡ L & ⇩[s, d, e1] L ≡ L2.
 #L1 #L2 #d #e2 #s #H elim H -L1 -L2 -d -e2