property S2 of strongly normalizing terms proved!

[helm.git] / matita / matita / contribs / lambda_delta / basic_2 / computation / cprs_tstc.ma

diff --git a/matita/matita/contribs/lambda_delta/basic_2/computation/cprs_tstc.ma b/matita/matita/contribs/lambda_delta/basic_2/computation/cprs_tstc.ma
index c7f49d1cf1f4fb6a9fc25235eadd6a4b08e500ed..35917450311b382e12b463868adda731a926d522 100644 (file)
--- a/matita/matita/contribs/lambda_delta/basic_2/computation/cprs_tstc.ma
+++ b/matita/matita/contribs/lambda_delta/basic_2/computation/cprs_tstc.ma
@@ -20,6 +20,11 @@ include "basic_2/computation/cprs_lcprs.ma".
 
 (* Forward lemmas involving same top term constructor ***********************)
 
+lemma cprs_fwd_cnf: ∀L,T. L ⊢ 𝐍[T] → ∀U. L ⊢ T ➡* U → T ≃ U.
+#L #T #HT #U #H
+>(cprs_inv_cnf1 … H HT) -L -T //
+qed-.
+
 (* Basic_1: was: pr3_iso_beta *)
 lemma cprs_fwd_beta: ∀L,V,W,T,U. L ⊢ ⓐV. ⓛW. T ➡* U →
                      ⓐV. ⓛW. T ≃ U ∨ L ⊢ ⓓV. T ➡* U.