the coimplication connective (start)

diff --git a/helm/matita/contribs/PREDICATIVE-TOPOLOGY/iff.ma b/helm/matita/contribs/PREDICATIVE-TOPOLOGY/iff.ma
new file mode 100644 (file)
index 0000000..e6475c5
--- /dev/null
+++ b/helm/matita/contribs/PREDICATIVE-TOPOLOGY/iff.ma
@@ -0,0 +1,25 @@
+(**************************************************************************)
+(*       ___                                                              *)
+(*      ||M||                                                             *)
+(*      ||A||       A project by Andrea Asperti                           *)
+(*      ||T||                                                             *)
+(*      ||I||       Developers:                                           *)
+(*      ||T||         The HELM team.                                      *)
+(*      ||A||         http://helm.cs.unibo.it                             *)
+(*      \   /                                                             *)
+(*       \ /        This file is distributed under the terms of the       *)
+(*        v         GNU General Public License Version 2                  *)
+(*                                                                        *)
+(**************************************************************************)
+
+set "baseuri" "cic:/matita/logic/iff".
+
+definition Iff : Prop \to Prop \to Prop \def
+   \lambda A,B. (A \to B) \land (B \to A).
+   
+ (*CSC: the URI must disappear: there is a bug now *)
+interpretation "logical iff" 'iff x y = (cic:/matita/logic/iff/Iff.con x y).
+
+notation < "hvbox(a break \liff b)" 
+  left associative with precedence 25
+for @{ 'iff $a $b }.

diff --git a/helm/matita/matita.lang b/helm/matita/matita.lang
index e99672a35f77d5cccdca100bc8f1bbbe63b7ef3b..0c181ee4480269bf55ec473df745108fc03e825e 100644 (file)
--- a/helm/matita/matita.lang
+++ b/helm/matita/matita.lang
@@ -170,6 +170,8 @@
      <keyword>Assign</keyword>
      <keyword>land</keyword>
      <keyword>lor</keyword>
+     <keyword>lnot</keyword>
+     <keyword>liff</keyword>
      <keyword>subst</keyword>
      <keyword>vdash</keyword>
      <keyword>iforall</keyword>