arithmetics for λδ

[helm.git] / matita / matita / contribs / lambdadelta / ground / arith / pnat.ma

diff --git a/matita/matita/contribs/lambdadelta/ground/arith/pnat.ma b/matita/matita/contribs/lambdadelta/ground/arith/pnat.ma
index 059a7a3322c39d394f5c69d419c85de4ce46f747..d90f8dd8d23ec00b536a5db1aeb06221aa0ab20d 100644 (file)
--- a/matita/matita/contribs/lambdadelta/ground/arith/pnat.ma
+++ b/matita/matita/contribs/lambdadelta/ground/arith/pnat.ma
@@ -38,6 +38,13 @@ lemma eq_inv_psucc_bi: injective … psucc.
 #p #q #H destruct //
 qed.
 
+lemma psucc_inv_refl (p): p = ↑p → ⊥.
+#p elim p -p
+[ #H destruct
+| #p #IH #H /3 width=1 by eq_inv_psucc_bi/
+]
+qed-.
+
 (* Basic constructions ******************************************************)
 
 lemma eq_pnat_dec (p1,p2:pnat): Decidable (p1 = p2).