From: Niklas Holsti <niklas.holsti@tidorum.invalid>
Subject: Re: orthogonal inheritance and extension aggregates
Date: Sat, 20 Jul 2013 10:54:44 +0300
Date: 2013-07-20T10:54:44+03:00 [thread overview]
Message-ID: <b4uu25F9it4U1@mid.individual.net> (raw)
In-Reply-To: <16rbbo5ajimr0.17dwtq00njx6u.dlg@40tude.net>
On 13-07-20 09:36 , Dmitry A. Kazakov wrote:
> On Sat, 20 Jul 2013 00:49:41 -0500, Randy Brukardt wrote:
>
>> "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de> wrote in message
>> news:igo2b70i4ox.t5duix9weguc$.dlg@40tude.net...
>> ...
>>> P.S. I don't know if Ada 2012 silently inherits from null extension. I
>>> heard that there was an intention to add the kludge. Though semantically
>>> broken it would save programs like yours.
>>
>> That's actually an Ada 2005 feature - see 3.9.3(4/2). One that I was against
>> because it introduces a maintenance problem (null extensions tend to turn
>> into non-null extensions over time, and once that happens, the feature stops
>> working).
>
> Right.
>
>> It appears that GNAT failed to properly implement this feature in the case
>> described by the OP.
>
> But the extension is null only *privately*.
The *private* extension looked non-null to me in the original post,
where an ellipsis marks the extension in the private part of the generic:
On 13-07-19 20:46 , Felix Krause wrote:
> I try to implement some feature via orthogonal inhertance like this:
>
> generic
> type Parent (<>) is abstract tagged private;
> package Extension is
> type Extended is abstract new Parent with private;
>
> -- operations of the extended type here
> private
> type Extended is abstract new Parent with record
> -- …
> end record;
> end Extension;
The visible extension to a non-abstract type was null:
> type Child is new Base.Extended with null record;
It seems to me that GNAT is working correctly on this code, assuming
that the private extension is not null.
--
Niklas Holsti
Tidorum Ltd
niklas holsti tidorum fi
. @ .
prev parent reply other threads:[~2013-07-20 7:54 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-07-19 17:46 orthogonal inheritance and extension aggregates Felix Krause
2013-07-19 18:00 ` Adam Beneschan
2013-07-22 16:02 ` Adam Beneschan
2013-07-22 18:44 ` Dmitry A. Kazakov
2013-07-22 18:59 ` Adam Beneschan
2013-07-22 19:19 ` Adam Beneschan
2013-07-22 22:03 ` Felix Krause
2013-07-19 19:05 ` Dmitry A. Kazakov
2013-07-20 5:49 ` Randy Brukardt
2013-07-20 6:36 ` Dmitry A. Kazakov
2013-07-20 7:54 ` Niklas Holsti [this message]
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