X-Git-Url: http://matita.cs.unibo.it/gitweb/?a=blobdiff_plain;f=helm%2Fsoftware%2Fmatita%2Flibrary%2Fnat%2Forders.ma;h=8053d50de55bfe8afc7d434243b17ceca34b9536;hb=5f6a2cf7134fda213ffc721ee7eebf5be30d7800;hp=3257e2e1a623d1f348f9d149bba0a0c7478355e2;hpb=50afaf262195266d156f594cff7e92a6e8898b3e;p=helm.git

diff --git a/helm/software/matita/library/nat/orders.ma b/helm/software/matita/library/nat/orders.ma
index 3257e2e1a..8053d50de 100644
--- a/helm/software/matita/library/nat/orders.ma
+++ b/helm/software/matita/library/nat/orders.ma
@@ -139,6 +139,19 @@ apply Hcut.assumption.rewrite < H1.
 apply not_le_Sn_n.
 qed.
 
+(*not lt*)
+theorem eq_to_not_lt: \forall a,b:nat.
+a = b \to a \nlt b.
+intros.
+unfold Not.
+intros.
+rewrite > H in H1.
+apply (lt_to_not_eq b b)
+[ assumption
+| reflexivity
+]
+qed.
+
 (* le vs. lt *)
 theorem lt_to_le : \forall n,m:nat. n<m \to n \leq m.
 simplify.intros.unfold lt in H.elim H.