X-Git-Url: http://matita.cs.unibo.it/gitweb/?a=blobdiff_plain;f=matita%2Flibrary%2Flogic%2Fconnectives.ma;h=5afc3e5dc29d7db0f45e812d244f6cd72e4ff7f6;hb=92d4c265cd2a6c5f56273ad5938a0da77bde2315;hp=bb08b8038bf51c37d533a0889c2493fd04fdc810;hpb=4c64aae84bbfd12abb64e7af5a640192b5051dc3;p=helm.git

diff --git a/matita/library/logic/connectives.ma b/matita/library/logic/connectives.ma
index bb08b8038..5afc3e5dc 100644
--- a/matita/library/logic/connectives.ma
+++ b/matita/library/logic/connectives.ma
@@ -82,3 +82,5 @@ interpretation "exists" 'exists \eta.x =
 inductive ex2 (A:Type) (P,Q:A \to Prop) : Prop \def
     ex_intro2: \forall x:A. P x \to Q x \to ex2 A P Q.
 
+definition iff :=
+ \lambda A,B. (A -> B) \land (B -> A).
\ No newline at end of file