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From: "Randy Brukardt" <randy@rrsoftware.com>
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Subject: Re: volatile vs aliased
Date: Thu, 6 Oct 2005 18:56:39 -0500
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Date: 2005-10-06T18:56:39-05:00
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"Robert A Duff" <bobduff@shell01.TheWorld.com> wrote in message
news:wcchdbufnck.fsf@shell01.TheWorld.com...
> "Jeffrey R. Carter" <spam@spam.com> writes:
>
> > Of course, if the C function has both pointer parameters and returns a
> > value, access parameters are the only thing available. Is ease of
> > interfacing to other languages another pro for allowing out and in out
> > parameters for functions, along with making side effects visible?
>
> Yes!  And that argument was brought up during the Ada 9X design.
> Apparently, it didn't convince people.

It also was one of the reasons for making null exclusions explicit in Ada
200Y. In Ada 95, access parameters exclude null automatically, making them
annoying for interfacing when you *do* need to use access values (such as
when null is a legitimate value - can't do that with "in out"). Using a
named access type is required -- but that can bring in accessibility checks
that are irrelevant. (Which is why I don't think I've ever successfully used
'Access on an object, I always have to change to 'Unchecked_Access.)

                           Randy.