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Subject: Re: Teaching new tricks to an old dog (C++ -->Ada)
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From: Mark Lorenzen <mark.lorenzen@surfpost.dk>
Date: 10 Mar 2005 22:22:09 +0100
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Date: 2005-03-10T22:22:09+01:00
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"Alex R. Mosteo" <devnull@mailinator.com> writes:

> 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.

You're welcome. But Randy (a language lawyer) put it in perspective
with the Ada 2005 standard in another posting, much better than what I
could do.


Regards,
- Mark Lorenzen