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From: "Alex R. Mosteo" <devnull@mailinator.com>
Newsgroups: comp.lang.ada
Subject: Re: Teaching new tricks to an old dog (C++ -->Ada)
Date: Thu, 10 Mar 2005 11:11:05 +0100
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Date: 2005-03-10T11:11:05+01:00
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Mark Lorenzen wrote:
> "Alex R. Mosteo" <devnull@mailinator.com> writes:
> 
> 
>>This is something I don't fully understand. IFAIK,
>>
>>procedure Proc (Blah : access Some_Type);
>>
>>access parameters raise an excepcion if null. So I don't get what adds
>>to the language the
>>
>>Blah : not null access ...
>>
>>construct.
> 
> 
> When using the "not null" access type, it is the responsibility of the
> caller to ensure that the parameter value is not null. This way the
> compiler can optimise away checks for a null value in the subprogram
> in question ("Proc" in your case)
> 
> Note that it is still the run-time system (and not the programmer),
> that performs the check, but it is only done once - before calling the
> subprogram. Often the check can be optimised away.

Thanks for the explanation.