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=-0.3 required=5.0 tests=BAYES_00,
	REPLYTO_WITHOUT_TO_CC autolearn=no autolearn_force=no version=3.4.4
X-Google-Thread: 103376,2a3157e5254b8223
X-Google-Attributes: gid103376,domainid0,public,usenet
X-Google-Language: ENGLISH,ASCII-7-bit
Path: 
 g2news1.google.com!news4.google.com!feeder1-2.proxad.net!proxad.net!feeder2-2.proxad.net!newsfeed.arcor.de!newsspool3.arcor-online.net!news.arcor.de.POSTED!not-for-mail
From: "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>
Subject: Re: Array slices and types
Newsgroups: comp.lang.ada
User-Agent: 40tude_Dialog/2.0.15.1
MIME-Version: 1.0
Content-Type: text/plain; charset="us-ascii"
Content-Transfer-Encoding: 7bit
Reply-To: mailbox@dmitry-kazakov.de
Organization: cbb software GmbH
References: <5886ab95-8744-4b72-b911-e4cb8889c7e7@d1g2000hsg.googlegroups.com>
 <1k5uib98w8fgw.bno6vggps1p3.dlg@40tude.net>
 <48ac6750$0$23587$4f793bc4@news.tdc.fi> <m2fxozo3qx.fsf@mac.com>
 <48acfbe8$0$23588$4f793bc4@news.tdc.fi>
Date: Thu, 21 Aug 2008 10:53:50 +0200
Message-ID: <mxlm26noiy7f$.r22nktgl3jiv.dlg@40tude.net>
NNTP-Posting-Date: 21 Aug 2008 10:53:52 CEST
NNTP-Posting-Host: 6cbce974.newsspool1.arcor-online.net
X-Trace: 
 DXC=@k?hfi8AQT8L2C_`koXfC5ic==]BZ:af>4Fo<]lROoR14nDHegD_]R5gG`ClfbHhY8DNcfSJ;bb[5IRnRBaCd<M>5;m3he=ol;5NXfNO_GQ]C9
X-Complaints-To: usenet-abuse@arcor.de
Xref: g2news1.google.com comp.lang.ada:1710
Date: 2008-08-21T10:53:52+02:00
List-Id: <comp.lang.ada>

On Thu, 21 Aug 2008 08:26:26 +0300, Niklas Holsti wrote:

> But doesn't this example show that it would be useful to have 'Base 
> also for array types?

For any type, actually.

Consider this language design fault:

procedure Initialize (X : in out S) is
begin
   Initialize (T (X));
   ... -- My stuff
end Initialize;

A call to Initialize should be done automatically, but it is not. So the
parent of S must be explicitly specified and known to all descendant. This
is a really *bad* thing:

package Foo is
   type S is new T with private;
private
   type S is new Private_Decendant_Of_T with ...;
end Foo;

What would happen if Private_Decendant_Of_T overrode Initialize of T? The
result would be an inability to publicly derive from S any new types if
Initialize should be extended!

S'Base could mend it:

procedure Initialize (X : in out S) is
begin
   (S"Base (X)).Initialize; -- Call to parent whatever it be
   ... -- My stuff
end Initialize;

Presently the only way is to override Initialize, Finalize and Adjust
everywhere, even if you actually don't want to extend them:

package Foo is
   type S is new T with private;
   overriding procedure Initialize (X : in out S); -- Have to do this!
private
   type S is new Private_Decendant_Of_T with ...;
end Foo;

-- 
Regards,
Dmitry A. Kazakov
http://www.dmitry-kazakov.de