X-Git-Url: http://matita.cs.unibo.it/gitweb/?p=helm.git;a=blobdiff_plain;f=matita%2Fmatita%2Fcontribs%2Flambdadelta%2Fground%2Farith%2Fnat_pred_succ.ma;h=ac01f0f8fc3aefbf78466e018ea478e8db5840f4;hp=a9a3ecd083e75801f0916497754cc10be3871368;hb=19b0a814861157ba05f23877d5cd94059f52c2e8;hpb=21de0d35017656c5a55528390b54b0b2ae395b44

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 a9a3ecd08..ac01f0f8f 100644
--- 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-.