- we introduced the pointer_step rc in the perspective of proving

[helm.git] / matita / matita / contribs / lambda_delta / basic_2 / grammar / lenv.ma

diff --git a/matita/matita/contribs/lambda_delta/basic_2/grammar/lenv.ma b/matita/matita/contribs/lambda_delta/basic_2/grammar/lenv.ma
index ba94738a85847b3a9327fd17d492797210605299..9988b3d4cc80275fa5f7211ca21b88a0bef6798c 100644 (file)
--- a/matita/matita/contribs/lambda_delta/basic_2/grammar/lenv.ma
+++ b/matita/matita/contribs/lambda_delta/basic_2/grammar/lenv.ma
@@ -37,4 +37,19 @@ interpretation "abbreviation (local environment)"
 interpretation "abstraction (local environment)"
    'DxAbst L T = (LPair L Abst T).
 
+(* Basic inversion lemmas ***************************************************)
+
+lemma destruct_lpair_lpair: ∀I1,I2,L1,L2,V1,V2. L1.ⓑ{I1}V1 = L2.ⓑ{I2}V2 →
+                            ∧∧L1 = L2 & I1 = I2 & V1 = V2.
+#I1 #I2 #L1 #L2 #V1 #V2 #H destruct /2 width=1/
+qed-.
+
+lemma discr_lpair_x_xy: ∀I,V,L. L = L.ⓑ{I}V → ⊥.
+#I #V #L elim L -L
+[ #H destruct
+| #L #J #W #IHL #H
+  elim (destruct_lpair_lpair … H) -H #H1 #H2 #H3 destruct /2 width=1/ (**) (* destruct lemma needed *)
+]
+qed-.
+
 (* Basic_1: removed theorems 2: chead_ctail c_tail_ind *)