helm/software/matita/contribs/PREDICATIVE-TOPOLOGY/iff.ma

   1 (**************************************************************************)
   2 (*       ___                                                              *)
   3 (*      ||M||                                                             *)
   4 (*      ||A||       A project by Andrea Asperti                           *)
   5 (*      ||T||                                                             *)
   6 (*      ||I||       Developers:                                           *)
   7 (*      ||T||         The HELM team.                                      *)
   8 (*      ||A||         http://helm.cs.unibo.it                             *)
   9 (*      \   /                                                             *)
  10 (*       \ /        This file is distributed under the terms of the       *)
  11 (*        v         GNU General Public License Version 2                  *)
  12 (*                                                                        *)
  13 (**************************************************************************)
  14
  15 (* STATO: COMPILA *)
  16
  17 set "baseuri" "cic:/matita/logic/iff".
  18
  19 include "../../library/logic/connectives.ma".
  20
  21 definition Iff : Prop \to Prop \to Prop \def
  22    \lambda A,B. (A \to B) \land (B \to A).
  23
  24  (*CSC: the URI must disappear: there is a bug now *)
  25 interpretation "logical iff" 'iff x y = (cic:/matita/logic/iff/Iff.con x y).
  26
  27 notation > "hvbox(a break \liff b)"
  28   left associative with precedence 25
  29 for @{ 'iff $a $b }.
  30
  31 notation < "hvbox(a break \leftrightarrow b)"
  32   left associative with precedence 25
  33 for @{ 'iff $a $b }.