X-Git-Url: http://matita.cs.unibo.it/gitweb/?a=blobdiff_plain;f=helm%2Fsoftware%2Fmatita%2Fnlibrary%2Flogic%2Fconnectives.ma;h=026e9216951c9224737b6493953317effd635369;hb=3d3d0248bf4770c63361f7805d2099b2a607f44d;hp=25fb2ce93c38784c9069fe19dcf8e01551e5275a;hpb=5799dca87fe5c1b5a3cc1f4869109fe75d055ecd;p=helm.git

diff --git a/helm/software/matita/nlibrary/logic/connectives.ma b/helm/software/matita/nlibrary/logic/connectives.ma
index 25fb2ce93..026e92169 100644
--- a/helm/software/matita/nlibrary/logic/connectives.ma
+++ b/helm/software/matita/nlibrary/logic/connectives.ma
@@ -39,3 +39,18 @@ ninductive Ex (A:Type) (P:A → CProp) : CProp ≝
     ex_intro: ∀x:A. P x → Ex A P.
 
 interpretation "exists" 'exists x = (Ex ? x).
+
+nrecord iff (A,B: CProp) : CProp ≝
+ { if: A → B;
+   fi: B → A
+ }.
+
+notation > "hvbox(a break \liff b)"
+  left associative with precedence 25
+for @{ 'iff $a $b }.
+
+notation "hvbox(a break \leftrightarrow b)"
+  left associative with precedence 25
+for @{ 'iff $a $b }.
+
+interpretation "logical iff" 'iff x y = (iff x y).