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: 103376,839916f6ca3b6404
X-Google-Attributes: gid103376,domainid0,public,usenet
X-Google-Language: ENGLISH,ASCII-7-bit
Path: 
 g2news2.google.com!news1.google.com!news.glorb.com!news2.glorb.com!feeder.erje.net!newsfeed.straub-nv.de!uucp.gnuu.de!newsfeed.arcor.de!newsspool2.arcor-online.net!news.arcor.de.POSTED!not-for-mail
From: "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>
Subject: Re: not null
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: <49ae93bc$0$31872$9b4e6d93@newsspool3.arcor-online.net>
  <KEwrl.43389$EO2.26870@newsfe04.iad>
 <761a4fb8-de91-43b3-b420-55dbc06a61e7@k9g2000prh.googlegroups.com>
  <qcauq45pgq84rvntrggh90hdd68ji6btl2@4ax.com>
 <75e0862b-cb8d-4f47-b55e-e2c6235997ea@n33g2000pri.googlegroups.com>
 <j8dvq4lmb7p7hr70h7k3elqv5k8lrvjcv5@4ax.com>
Date: Thu, 5 Mar 2009 16:06:22 +0100
Message-ID: <1bydip4ahvzhy$.fluevvq5h3pi$.dlg@40tude.net>
NNTP-Posting-Date: 05 Mar 2009 16:06:22 CET
NNTP-Posting-Host: 1ae4b7c4.newsspool2.arcor-online.net
X-Trace: 
 DXC=>;Da4Z?R6lRYQ5E:l<XC@SA9EHlD;3YcR4Fo<]lROoRQ^YC2XCjHcbYPE31VF^PL]RDNcfSJ;bb[UFCTGGVUmh?TLK[5LiR>kgR0B=5G?=hhR_
X-Complaints-To: usenet-abuse@arcor.de
Xref: g2news2.google.com comp.lang.ada:4941
Date: 2009-03-05T16:06:22+01:00
List-Id: <comp.lang.ada>

On Thu, 05 Mar 2009 11:32:13 +0000, Brian Drummond wrote:

> On Wed, 4 Mar 2009 17:47:03 -0800 (PST), Adam Beneschan <adam@irvine.com> wrote:
> 
>>You could also make the "end of list" point to some special dummy
>>object. 
> 
> I don't see that as semantically different from a null pointer.
> Which perhaps just helps to make your point

Well, many lists are never empty. Such lists (single or doubly-linked) can
be made circular. This strategy has several advantages. One of them is that
null pointers are never used. (An item outside any list points to itself.)

(Granted, a wrongly implemented list iteration may cycle rather than
crash.)

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