X-Git-Url: http://matita.cs.unibo.it/gitweb/?a=blobdiff_plain;f=matita%2Fmatita%2Flib%2Fbasics%2Fsets.ma;h=2f570c18feb503e1da38186bf9455a8c0b9e1018;hb=b5cb5cc7230870f757aadbe6b43ee146fe485a6d;hp=cdc6ac9e8e278e19c3d7957bf600f7150ae1d895;hpb=38b251338be469c7bcd75cb9f243fad9ba8f0907;p=helm.git

diff --git a/matita/matita/lib/basics/sets.ma b/matita/matita/lib/basics/sets.ma
index cdc6ac9e8..2f570c18f 100644
--- a/matita/matita/lib/basics/sets.ma
+++ b/matita/matita/lib/basics/sets.ma
@@ -10,6 +10,7 @@
       V_______________________________________________________________ *)
 
 include "basics/logic.ma".
+include "basics/core_notation/singl_1.ma".
 
 (**** a subset of A is just an object of type A→Prop ****)
 
@@ -116,4 +117,4 @@ qed.
 (* substraction *)
 lemma substract_def:∀U.∀A,B:U→Prop. A-B ≐ A ∩ ¬B.
 #U #A #B #w normalize /2/
-qed.
\ No newline at end of file
+qed.