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From: Mats Weber <Mats.Weber@elca-matrix.ch>
Subject: Re: Equality operator overloading in ADA 83
Date: 1997/04/22
Message-ID: <335CB216.3197@elca-matrix.ch>#1/1
X-Deja-AN: 236666163
References: <01bc4e9b$ac0e7fa0$72041dc2@lightning>
Organization: ELCA Matrix SA
Reply-To: Mats.Weber@elca-matrix.ch
Newsgroups: comp.lang.ada
Date: 1997-04-22T00:00:00+00:00
List-Id: <comp.lang.ada>


> In other words, how do I tell my "equal" function to be an equality
> operator, authorized to be renamed into "="? HELP! :)

There is a way, but it is contrived (Ada 83 was designed to make it
impossible, but a hole was left. Use at your own risk as some compilers
may not like it very much, and read the other replies about the
reemergence of predefined "="):

   generic
      type T is limited private;
      with function "=" (X, Y : T) return BOOLEAN is <>;
   package MESS_UP_EQUALITY is

      package ENCLOSE_EQUALITY is

         function "=" (X, Y : T) return BOOLEAN
            renames MESS_UP_EQUALITY."=";

      end ENCLOSE_EQUALITY;

   end MESS_UP_EQUALITY;

   type T is ...;

   function Equal (L, R : T) return Boolean;

   package T_Equality is new MESS_UP_EQUALITY(T => T, "=" => Equal);

   function "=" (L, R : T) return Boolean
      renames T_Equality.Enclose_Equality."=";