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Date: Thu, 5 Mar 2009 19:53:53 +0000
From: Jack Mitchell <jack@home9999.plus.com>
Newsgroups: comp.lang.ada
Subject: Re: not null
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In message <qcauq45pgq84rvntrggh90hdd68ji6btl2@4ax.com>, Brian Drummond 
<brian_drummond@btconnect.com> writes
>On Wed, 4 Mar 2009 08:09:56 -0800 (PST), Adam Beneschan 
><adam@irvine.com> wrote:
>
>>On Mar 4, 6:56 am, Hyman Rosen <hyro...@mail.com> wrote:
>>> Georg Bauhaus wrote:
>>> > As said to have been seen on /.
>>> > another financial disaster, again caused
>>> > by making references to nothing, in Algol W,
>>> >http://qconlondon.com/london-2009/presentation/Null+References:+The+B...
>>>
>>> You are misreading the abstract. First of all, it's not
>>> about some particular incident. He's talking about the
>>> overall impact. Second, he's not talking about failure
>>> to check for null references, he's talking about having
>>> null references at all, so Ada is no better.
>>
>>I'm having difficulty understanding the point.  You have to have the
>>idea of the lack of a reference.  How else would you implement a
>>linked list abstraction?
>
>Possibly by pointing from the end back to the list head.
>
>It would make the "end of list" test more expensive (the head might have to be
>kept in a register or passed around as another argument). I don't think 
>it would
>be pretty, but can't see any fundamental reason why it shouldn't work.
>
>- Brian

The other way to avoid needing null references is to point back not to 
the start of the list, but to your self.

-- 
Jack Mi_Remove_tchell