X-Git-Url: http://matita.cs.unibo.it/gitweb/?a=blobdiff_plain;f=matita%2Fmatita%2Fcontribs%2Flambdadelta%2Fbasic_2%2Frt_transition%2Flfpx_length.ma;h=7b194bd71555d668d08e433494773fff846ab9b1;hb=47a745462a714af9d65cea7b61af56524bd98fa1;hp=6e4acfac484b37e12bfd924d3bf6ef09aade3a35;hpb=4a3e161726553a41fe68b22f111de3b8df1a9fb6;p=helm.git

diff --git a/matita/matita/contribs/lambdadelta/basic_2/rt_transition/lfpx_length.ma b/matita/matita/contribs/lambdadelta/basic_2/rt_transition/lfpx_length.ma
index 6e4acfac4..7b194bd71 100644
--- a/matita/matita/contribs/lambdadelta/basic_2/rt_transition/lfpx_length.ma
+++ b/matita/matita/contribs/lambdadelta/basic_2/rt_transition/lfpx_length.ma
@@ -19,5 +19,16 @@ include "basic_2/rt_transition/lfpx.ma".
 
 (* Forward lemmas with length for local environments ************************)
 
+(* Basic_2A1: uses: lpx_fwd_length *)
 lemma lfpx_fwd_length: ∀h,G,L1,L2,T. ⦃G, L1⦄ ⊢ ⬈[h, T] L2 → |L1| = |L2|.
 /2 width=3 by lfxs_fwd_length/ qed-.
+
+(* Inversion lemmas with length for local environments **********************)
+
+lemma lfpx_inv_zero_length: ∀h,G,Y1,Y2. ⦃G, Y1⦄ ⊢ ⬈[h, #0] Y2 →
+                            ∨∨ ∧∧ Y1 = ⋆ & Y2 = ⋆
+                             | ∃∃I,L1,L2,V1,V2. ⦃G, L1⦄ ⊢ ⬈[h, V1] L2 &
+                                                ⦃G, L1⦄ ⊢ V1 ⬈[h] V2 &
+                                                Y1 = L1.ⓑ{I}V1 & Y2 = L2.ⓑ{I}V2
+                             |∃∃I,L1,L2. |L1| = |L2| & Y1 = L1.ⓤ{I} & Y2 = L2.ⓤ{I}.
+/2 width=1 by lfxs_inv_zero_length/ qed-.