- bug fix in the induction for the closure property

[helm.git] / matita / matita / contribs / lambdadelta / basic_2 / substitution / fqus.ma

diff --git a/matita/matita/contribs/lambdadelta/basic_2/substitution/fqus.ma b/matita/matita/contribs/lambdadelta/basic_2/substitution/fqus.ma
index f33a942a681e6b4e9b02e7ed39442bf05a960cca..325be4b397a4aff7c24d7e24480a4d46d074ccad 100644 (file)
--- a/matita/matita/contribs/lambdadelta/basic_2/substitution/fqus.ma
+++ b/matita/matita/contribs/lambdadelta/basic_2/substitution/fqus.ma
@@ -73,3 +73,11 @@ lemma fqus_fwd_fw: ∀G1,G2,L1,L2,T1,T2. ⦃G1, L1, T1⦄ ⊃* ⦃G2, L2, T2⦄
 #G1 #G2 #L1 #L2 #T1 #T2 #H @(fqus_ind … H) -L2 -T2
 /3 width=3 by fquq_fwd_fw, transitive_le/
 qed-.
+
+(* Basic inversion lemmas ***************************************************)
+
+lemma fqup_inv_step_sn: ∀G1,G2,L1,L2,T1,T2. ⦃G1, L1, T1⦄ ⊃+ ⦃G2, L2, T2⦄ →
+                        ∃∃G,L,T. ⦃G1, L1, T1⦄ ⊃ ⦃G, L, T⦄ & ⦃G, L, T⦄ ⊃* ⦃G2, L2, T2⦄.
+#G1 #G2 #L1 #L2 #T1 #T2 #H @(fqup_ind_dx … H) -G1 -L1 -T1 /2 width=5 by ex2_3_intro/
+#G1 #G #L1 #L #T1 #T #H1 #_ * /4 width=9 by fqus_strap2, fqu_fquq, ex2_3_intro/
+qed-.