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: a07f3367d7,dbbbb21ed7f581b
X-Google-Attributes: gida07f3367d7,public,usenet
X-Google-NewGroupId: yes
X-Google-Language: ENGLISH,ASCII-7-bit
Path: 
 g2news1.google.com!news4.google.com!feeder.news-service.com!feeder.erje.net!news.osn.de!diablo1.news.osn.de!noris.net!newsfeed.arcor.de!newsspool4.arcor-online.net!news.arcor.de.POSTED!not-for-mail
From: "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>
Subject: Re: Operation can be dispatching in only one type
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: <691d6892-bc5e-4d81-8025-c36556bf2593@13g2000prl.googlegroups.com>
 <he2a6a$du1$1@aioe.org>
Date: Thu, 19 Nov 2009 09:32:34 +0100
Message-ID: <14i0ogkos0ggq.1j3iq8bn1g39a.dlg@40tude.net>
NNTP-Posting-Date: 19 Nov 2009 09:32:34 CET
NNTP-Posting-Host: a0dd1e7a.newsspool4.arcor-online.net
X-Trace: 
 DXC=QN?[QnW5l]^cHPTNZh_e7Q4IUK<Cl32<Q4Fo<]lROoRQ8kF<OcfhCO[;?E3AjS4WP[[6LHn;2LCV^7enW;^6ZC`TIXm65S@:3>_a<GHblNL=YR
X-Complaints-To: usenet-abuse@arcor.de
Xref: g2news1.google.com comp.lang.ada:8153
Date: 2009-11-19T09:32:34+01:00
List-Id: <comp.lang.ada>

On Thu, 19 Nov 2009 02:23:07 +0000 (UTC), tmoran@acm.org wrote:

>> package Documents is
>>
>>     type Document is abstract tagged private;
>>     type Text_Region is abstract tagged private;
>>     type Marker is abstract tagged private;
>>   ...
>>     procedure Move_Text (Doc  : in out Document;
>>                          From : in Text_Region;
>>                          To   : in Marker)
>>        is abstract;
> 
>   There's really no way at compile time to require a particular
> relationship between two (or more) arbitrary parameters to a procedure.
> If that's necessary, you usually combine them into a single object that's
> a single parameter.

Yes, this is why I consider these cases single dispatch on a tuple of
types. It is like

   type Editing is interface (Document, Region, Marker);

And the operations are in fact defined on Editing, which has only one tag.

> Thus if a Document could have up to 10 defined
> Text_Regions and 20 Markers one could say
> 
>       type Document is abstract tagged private;
>       -- Presumably includes an array or list of appropriate Text_Region
>       -- descriptors and of Marker descriptors.
> 
>       type Text_Region_Ids is range 1 .. 10;
>       type Marker_Ids is range 1 .. 20;
> 
>       procedure Move_Text (Doc  : in out Document;
>                            From : in Text_Region_Ids;
>                            To   : in Marker_Ids)
>          is abstract;

It is not ADT. ID does not have finalization and cannot refer to a specific
Document. You will not be able to transparently manage Regions and Markers.

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