From mboxrd@z Thu Jan  1 00:00:00 1970
X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on polar.synack.me
X-Spam-Level: 
X-Spam-Status: No, score=-1.9 required=5.0 tests=BAYES_00 autolearn=ham
	autolearn_force=no version=3.4.4
X-Google-Language: ENGLISH,ASCII-7-bit
X-Google-Thread: 103376,1116ece181be1aea
X-Google-Attributes: gid103376,public
X-Google-ArrivalTime: 2003-09-23 18:55:55 PST
Path: 
 archiver1.google.com!news1.google.com!newsfeed.stanford.edu!headwall.stanford.edu!newshub.sdsu.edu!elnk-nf2-pas!newsfeed.earthlink.net!stamper.news.pas.earthlink.net!stamper.news.atl.earthlink.net!newsread1.news.atl.earthlink.net.POSTED!not-for-mail
Sender: mheaney@MHEANEYX200
Newsgroups: comp.lang.ada
Subject: Re: Is the Writing on the Wall for Ada?
References: <mailman.20.1062997816.295.comp.lang.ada@ada.eu.org>
 <q697b.8261$w41.4773@nwrdny02.gnilink.net> <wvbrad9emn3u.fsf@sun.com>
 <u3cez82oh.fsf@earthlink.net> <wvbr65jul87d.fsf@sun.com>
 <uhe3d7hmj.fsf@earthlink.net> <xXt9b.4926$U41.4024@nwrdny01.gnilink.net>
 <ud6e178aw.fsf@earthlink.net>
 <568ede3c.0309160929.1d0d3d95@posting.google.com>
 <3F67AFB9.7040001@attbi.com> <OJO9b.1195$U6.228@nwrdny03.gnilink.net>
 <3F6F0841.60607@attbi.com> <1064244399.683441@master.nyc.kbcfp.com>
 <3F70021A.2010305@attbi.com> <1064320198.65725@master.nyc.kbcfp.com>
From: Matthew Heaney <matthewjheaney@earthlink.net>
Message-ID: <upthrvthe.fsf@earthlink.net>
User-Agent: Gnus/5.09 (Gnus v5.9.0) Emacs/21.3
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Date: Wed, 24 Sep 2003 01:55:54 GMT
NNTP-Posting-Host: 65.110.133.134
X-Complaints-To: abuse@earthlink.net
X-Trace: newsread1.news.atl.earthlink.net 1064368554 65.110.133.134 (Tue,
 23 Sep 2003 18:55:54 PDT)
NNTP-Posting-Date: Tue, 23 Sep 2003 18:55:54 PDT
Organization: EarthLink Inc. -- http://www.EarthLink.net
Xref: archiver1.google.com comp.lang.ada:42834
Date: 2003-09-24T01:55:54+00:00
List-Id: <comp.lang.ada>

Hyman Rosen <hyrosen@mail.com> writes:

> Oh, by the way, is it true that "virtual" methods of Ada objects can
> only be procedures and not functions?

Huh?  Of course not:

   type T is abstract tagged null record;

   function Op (O : T) return Integer is abstract;

You might be thinking of functions that return a tagged type:

   function Op2 return T is abstract;

In the cases where there's a primitive op that returns the type, then
you must override the function or the type "goes abstract."  Think about
this:

   O : T'Class := ...;
begin
   O := Op2;  -- I think that will work

Here we dispatch on the return type.  There are also "tag indeterminate"
expressions, where the compiler figures out which function to call based
on context.