From: "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>
Subject: Re: tagged record child: override constructor?
Date: Wed, 14 Sep 2005 09:49:13 +0200
Date: 2005-09-14T09:49:06+02:00 [thread overview]
Message-ID: <1idpvzxcxfckw.mrs8nw3eu4ks$.dlg@40tude.net> (raw)
In-Reply-To: 87vf14him5.fsf@ludovic-brenta.org
On Tue, 13 Sep 2005 21:29:06 +0200, Ludovic Brenta wrote:
> Martin Krischik <krischik@users.sourceforge.net> writes:
>> That's because all class members are virtual in Ada.
>
> I think this needs to be elaborated on.
>
> All _primitive operations of a tagged type_ are _potentially_
> "virtual" in Ada. Each caller of such a primitive operation decides,
> at the call site, whether the dispatching is static or dynamic.
Ada's model is quite simple and logical. If T appears as a formal parameter
or the result of a primitive operation of T, then this parameter is
controlled (= the operation can dispatch on it.)
Dispatching is determined not by any site but exclusively by the actual
parameter type. It must be of T'Class.
For this reason re-dispatching never happens. To re-dispatch, one should
explicitly convert T to T'Class.
> In contrast, in (my recollection of) C++, all virtual methods dispatch
> dynamically from all call sites: the decision is not made at the point
> of call but at the point of definition of the method.
C++ model is more tricky and in some aspects more limited. Only the prefix
(distinguished) parameter can be controlled (the "this-parameter".) The
result cannot be controlled as well. There is no difference between T and
T'Class (the source of countless problems.) So all operations re-dispatch
except for constructors and destructors, which don't. I.e. it is rather C++
where the call site determines whether a virtual function dispatches.
--
Regards,
Dmitry A. Kazakov
http://www.dmitry-kazakov.de
next prev parent reply other threads:[~2005-09-14 7:49 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2005-09-13 5:58 tagged record child: override constructor? sean.gilbertson
2005-09-13 6:39 ` David Trudgett
2005-09-13 7:32 ` Dmitry A. Kazakov
2005-09-13 7:56 ` tmoran
2005-09-13 15:23 ` sean.gilbertson
2005-09-13 17:37 ` Martin Krischik
2005-09-13 19:29 ` Ludovic Brenta
2005-09-14 7:49 ` Dmitry A. Kazakov [this message]
2005-09-14 9:05 ` Maciej Sobczak
2005-09-14 13:20 ` Dmitry A. Kazakov
2005-09-14 13:52 ` Hyman Rosen
2005-09-14 16:47 ` Dmitry A. Kazakov
2005-09-14 17:16 ` Hyman Rosen
2005-09-14 20:20 ` Dmitry A. Kazakov
2005-09-14 20:34 ` Georg Bauhaus
2005-09-14 20:56 ` Hyman Rosen
2005-09-15 7:31 ` Dmitry A. Kazakov
2005-09-15 13:19 ` Hyman Rosen
2005-09-15 13:45 ` Maciej Sobczak
2005-09-15 17:45 ` Dmitry A. Kazakov
2005-09-15 18:54 ` Hyman Rosen
2005-09-16 9:32 ` Dmitry A. Kazakov
2005-09-16 14:52 ` Hyman Rosen
2005-09-16 15:33 ` Jean-Pierre Rosen
2005-09-16 18:37 ` Hyman Rosen
2005-09-16 21:03 ` Dmitry A. Kazakov
2005-09-16 21:33 ` Hyman Rosen
[not found] ` <98ox2x9xvj9z.1uh92dslhvt4g.dlg@40tude.net>
2005-09-17 12:47 ` Georg Bauhaus
2005-09-17 15:56 ` Dmitry A. Kazakov
2005-09-14 16:14 ` Martin Krischik
2005-09-14 16:57 ` Dmitry A. Kazakov
2005-09-14 18:35 ` Martin Krischik
2005-09-14 9:28 ` Alex R. Mosteo
2005-09-14 16:10 ` Martin Krischik
2005-09-13 9:33 ` Georg Bauhaus
2005-09-13 16:37 ` Jeffrey Carter
2005-09-13 18:55 ` Robert A Duff
2005-09-13 22:18 ` Jeffrey Carter
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