X-Git-Url: http://matita.cs.unibo.it/gitweb/?a=blobdiff_plain;f=matita%2Fmatita%2Fcontribs%2Flambda_delta%2Fbasic_2%2Fcomputation%2Fcprs_cprs.ma;h=5d4d74399a2efc959c448d0093bce6de4d8f0306;hb=69644bb333b2862a5ff2ff434df8830e854e3385;hp=a71c773bc9a40a3fff886b39fbc5decac4f73f1e;hpb=ea83c19f4cac864dd87eb059d8aeb2343eba480f;p=helm.git

diff --git a/matita/matita/contribs/lambda_delta/basic_2/computation/cprs_cprs.ma b/matita/matita/contribs/lambda_delta/basic_2/computation/cprs_cprs.ma
index a71c773bc..5d4d74399 100644
--- a/matita/matita/contribs/lambda_delta/basic_2/computation/cprs_cprs.ma
+++ b/matita/matita/contribs/lambda_delta/basic_2/computation/cprs_cprs.ma
@@ -130,6 +130,16 @@ lapply (IHV1 T1 T1 ?) -IHV1 // #HV1
 @(cprs_trans … HV1) -HV1 /2 width=1/
 qed.
 
+lemma cprs_beta_dx: ∀L,V1,V2,W,T1,T2.
+                    L ⊢ V1 ➡ V2 → L.ⓛW ⊢ T1 ➡* T2 → L ⊢ ⓐV1.ⓛW.T1 ➡* ⓓV2.T2.
+#L #V1 #V2 #W #T1 #T2 #HV12 #HT12 @(cprs_ind … HT12) -T2
+[ /3 width=1/
+| -HV12 #T #T2 #_ #HT2 #IHT1
+  lapply (cpr_lsubs_trans … HT2 (L.ⓓV2) ?) -HT2 /2 width=1/ #HT2
+  @(cprs_trans … IHT1) -V1 -W -T1 /3 width=1/
+]
+qed.
+
 (* Basic_1: was only: pr3_pr2_pr3_t pr3_wcpr0_t *)
 lemma lcpr_cprs_trans: ∀L1,L2. L1 ⊢ ➡ L2 →
                        ∀T1,T2. L2 ⊢ T1 ➡* T2 → L1 ⊢ T1 ➡* T2.