update in delayed_updating

[helm.git] / matita / matita / contribs / lambdadelta / delayed_updating / substitution / fsubst_eq.ma

diff --git a/matita/matita/contribs/lambdadelta/delayed_updating/substitution/fsubst_eq.ma b/matita/matita/contribs/lambdadelta/delayed_updating/substitution/fsubst_eq.ma
index c3f6cfa11849a560be7114edeaa35ac2fa955327..c3a985716d5427f56434ec93bc6503420a04f7e6 100644 (file)
--- a/matita/matita/contribs/lambdadelta/delayed_updating/substitution/fsubst_eq.ma
+++ b/matita/matita/contribs/lambdadelta/delayed_updating/substitution/fsubst_eq.ma
@@ -19,6 +19,15 @@ include "delayed_updating/syntax/prototerm_eq.ma".
 
 (* Constructions with subset_equivalence ************************************)
 
+lemma fsubst_empty_rc (t) (u):
+      u ⇔ t[⋔𝐞←u].
+#t #u @conj #p
+[ #Hp /3 width=3 by or_introl, ex2_intro/ ]
+* *
+[ #r #Hr #H0 destruct // ]
+#H1p #H2p elim H2p -H2p //
+qed.
+
 lemma subset_inclusion_fsubst_bi (t1) (t2) (u1) (u2) (p):
       t1 ⊆ t2 → u1 ⊆ u2 → t1[⋔p←u1] ⊆ t2[⋔p←u2].
 #t1 #t2 #u1 #u2 #p #Ht #Hu #q * *