From: "Matthew Heaney" <matthew_heaney@acm.org>
Subject: Re: Newbie Access Types
Date: 1999/08/27
Date: 1999-08-27T00:00:00+00:00 [thread overview]
Message-ID: <37c70029@news1.us.ibm.net> (raw)
In-Reply-To: wcc4shlgtdw.fsf@world.std.com
In article <wcc4shlgtdw.fsf@world.std.com> , Robert A Duff
<bobduff@world.std.com> wrote:
> Also, in Ada 95, we have anonymous access types (for parameters and
> discriminants), and they have no null value, so it's not possible to
> initialize such parameters to null.
One thing I would have liked for inclusion is subtypes for named access
types. That way you could declare a subtype that excludes null:
type T_Access_Base is access all T;
subtype T_Access is T_Access_Base range not null;
-- or some other syntax
It's occasionally necessary to have a parameter of a named access type, and
at the same type require that a non-null value be passed in. It would be
nice to have the compiler do the check, that we now have to do manually.
--
Matt
It is impossible to feel great confidence in a negative theory which has
always rested its main support on the weak points of its opponent.
Joseph Needham, "A Mechanistic Criticism of Vitalism"
prev parent reply other threads:[~1999-08-27 0:00 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
1999-08-18 0:00 Newbie Access Types Ronald Ayoub
1999-08-18 0:00 ` Matthew Heaney
1999-08-25 0:00 ` Nick Roberts
1999-08-27 0:00 ` Robert A Duff
1999-08-27 0:00 ` Matthew Heaney [this message]
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