/*
 * @(#)$Id: iff,v 1.2 1995/06/06 18:40:23 img Exp $
 *
 * $Log: iff,v $
 * Revision 1.2  1995/06/06 18:40:23  img
 * 	* added header
 *
 */

x<=>y <==>(x=>y)#(y=>x).
