From: "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>
Subject: Re: abstract types and subprograms
Date: Tue, 20 May 2014 13:55:25 +0200
Date: 2014-05-20T13:55:25+02:00 [thread overview]
Message-ID: <7puqh5yz4dyf.pov2dgfr2ky$.dlg@40tude.net> (raw)
In-Reply-To: llfad4$he$1@speranza.aioe.org
On Tue, 20 May 2014 13:22:30 +0300, Victor Porton wrote:
> By the philosophy of programming From_Handle should be non-abstract but
> return an abstract object, and From_Handle should be automatically
> overridden for descendants non-abstract objects.
>
> What is wrong?
You cannot automatically override without knowing the implementation, which
you don't in advance. If you know it, then it is same for all class. See
below.
> -- rdf-base.ads
> with Ada.Finalization;
> with Interfaces.C.Pointers;
>
> package RDF.Base is
>
> -- Internal
> type Dummy_Record is null record;
>
> -- Internal
> type Dummy_Record_Access is access Dummy_Record;
>
> type Base_Object is abstract new Ada.Finalization.Limited_Controlled with
> private;
>
> function Get_Handle(Object: Base_Object) return Dummy_Record_Access with
> Inline;
>
> function From_Handle(Handle: Dummy_Record_Access) return Base_Object with
> Inline;
function From_Handle(Handle: Dummy_Record_Access) return Base_Object'Class;
Logically, a handle can point on an object of any type derived from
Base_Object, so it is a class.
--
Regards,
Dmitry A. Kazakov
http://www.dmitry-kazakov.de
next prev parent reply other threads:[~2014-05-20 11:55 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-05-20 10:22 abstract types and subprograms Victor Porton
2014-05-20 10:51 ` mockturtle
2014-05-20 11:45 ` Victor Porton
2014-05-20 16:27 ` Robert A Duff
2014-05-20 19:52 ` Dmitry A. Kazakov
2014-05-24 18:49 ` Robert A Duff
2014-05-24 19:41 ` Dmitry A. Kazakov
2014-05-20 11:55 ` Dmitry A. Kazakov [this message]
2014-05-20 12:28 ` Victor Porton
2014-05-20 14:11 ` Dmitry A. Kazakov
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