X-Git-Url: http://matita.cs.unibo.it/gitweb/?a=blobdiff_plain;f=helm%2Fmatita%2Flibrary%2FZ%2Fplus.ma;h=d2e6ec2b0d2dbe7357814a810d649761b44a4194;hb=33a02e0b639217093eb63f30169aaa6ac8c78907;hp=b1942d209f45077d6060ba5f993ccbea2041ca89;hpb=15753bd130b39be9854894898154163ba036d4b0;p=helm.git

diff --git a/helm/matita/library/Z/plus.ma b/helm/matita/library/Z/plus.ma
index b1942d209..d2e6ec2b0 100644
--- a/helm/matita/library/Z/plus.ma
+++ b/helm/matita/library/Z/plus.ma
@@ -286,8 +286,7 @@ intro.simplify.reflexivity.
 simplify.reflexivity.
 qed.
 
-(* --x non gli piace, ma lo stampa *)
-theorem Zopp_Zopp: \forall x:Z. -(-x) = x.
+theorem Zopp_Zopp: \forall x:Z. --x = x.
 intro. elim x.
 reflexivity.reflexivity.reflexivity.
 qed.