X-Git-Url: http://matita.cs.unibo.it/gitweb/?a=blobdiff_plain;f=matita%2Fmatita%2Fcontribs%2Flambdadelta%2Fground%2Farith%2Fnat_pred_succ.ma;h=ac01f0f8fc3aefbf78466e018ea478e8db5840f4;hb=19b0a814861157ba05f23877d5cd94059f52c2e8;hp=f21156455af3542b7c4a05003e72d92a83c36eb9;hpb=68e028d053806177e218ee1a5f8778d3011bef83;p=helm.git

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 f21156455..ac01f0f8f 100644
--- a/matita/matita/contribs/lambdadelta/ground/arith/nat_pred_succ.ma
+++ b/matita/matita/contribs/lambdadelta/ground/arith/nat_pred_succ.ma
@@ -17,9 +17,17 @@ include "ground/arith/nat_pred.ma".
 
 (* PREDECESSOR FOR NON-NEGATIVE INTEGERS ************************************)
 
-(* Rewrites with nsucc ******************************************************)
+(* Constructions with nsucc *************************************************)
 
 (*** pred_Sn pred_S *)
 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-.