arithmetics for λδ

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

diff --git a/matita/matita/contribs/lambdadelta/ground/arith/nat_pred_succ.ma b/matita/matita/contribs/lambdadelta/ground/arith/nat_pred_succ.ma
index a9a3ecd083e75801f0916497754cc10be3871368..ac01f0f8fc3aefbf78466e018ea478e8db5840f4 100644 (file)
--- a/matita/matita/contribs/lambdadelta/ground/arith/nat_pred_succ.ma
+++ b/matita/matita/contribs/lambdadelta/ground/arith/nat_pred_succ.ma
@@ -23,3 +23,11 @@ include "ground/arith/nat_pred.ma".
 lemma npred_succ (n): n = ↓↑n.
 * //
 qed.
+
+(* Inversion with nsucc *****************************************************)
+
+(*** nat_split *)
+lemma nat_split (n): ∨∨ 𝟎 = n | n = ↑↓n.
+#n @(nat_ind_succ … n) -n
+/2 width=1 by or_introl, or_intror/
+qed-.