advances on csx towards strong normalization of rt-computation ,,,

[helm.git] / matita / matita / contribs / lambdadelta / basic_2 / static / lfxs.ma

diff --git a/matita/matita/contribs/lambdadelta/basic_2/static/lfxs.ma b/matita/matita/contribs/lambdadelta/basic_2/static/lfxs.ma
index a2f6816349f65e35b29f149e44d9ec32e30c52df..9f0a1a4865522b6c685acbf242e721c207a2027a 100644 (file)
--- a/matita/matita/contribs/lambdadelta/basic_2/static/lfxs.ma
+++ b/matita/matita/contribs/lambdadelta/basic_2/static/lfxs.ma
@@ -43,7 +43,7 @@ definition R_confluent2_lfxs: relation4 (relation3 lenv term term)
                               ∀L1. L0 ⦻*[RP1, T0] L1 → ∀L2. L0 ⦻*[RP2, T0] L2 →
                               ∃∃T. R2 L1 T1 T & R1 L2 T2 T.
 
-(* Basic properties ***********************************************************)
+(* Basic properties *********************************************************)
 
 lemma lfxs_atom: ∀R,I. ⋆ ⦻*[R, ⓪{I}] ⋆.
 /3 width=3 by lexs_atom, frees_atom, ex2_intro/
@@ -253,6 +253,13 @@ lemma lfxs_fwd_pair_sn: ∀R,I,L1,L2,V,T. L1 ⦻*[R, ②{I}V.T] L2 → L1 ⦻*[R
 #R * /2 width=4 by lfxs_fwd_flat_sn, lfxs_fwd_bind_sn/
 qed-.
 
+lemma lfxs_fwd_dx: ∀R,I,L1,K2,T,V2. L1 ⦻*[R, T] K2.ⓑ{I}V2 →
+                   ∃∃K1,V1. L1 = K1.ⓑ{I}V1.
+#R #I #L1 #K2 #T #V2 * #f elim (pn_split f) * #g #Hg #_ #Hf destruct
+[ elim (lexs_inv_push2 … Hf) | elim (lexs_inv_next2 … Hf) ] -Hf #K1 #V1 #_ #_ #H destruct
+/2 width=3 by ex1_2_intro/
+qed-.
+
 (* Basic_2A1: removed theorems 24:
               llpx_sn_sort llpx_sn_skip llpx_sn_lref llpx_sn_free llpx_sn_gref
               llpx_sn_bind llpx_sn_flat