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From: "Randy Brukardt" <randy@rrsoftware.com>
Newsgroups: comp.lang.ada
Subject: Re: Inherited Methods and such
Date: Thu, 27 Sep 2007 19:35:22 -0500
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Date: 2007-09-27T19:35:22-05:00
List-Id: <comp.lang.ada>

"Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de> wrote in message
news:1tovavprv3hg2$.w3sgselxd5ob$.dlg@40tude.net...
> On Thu, 27 Sep 2007 09:39:46 -0400, Robert A Duff wrote:
>
> >  If the answer is
> > "no", please give a realistic example where dispatching during
> > construction makes sense.
>
> You construct a GUI window. There is a hierarchy of. The base constructor
> might wish to know what kind of border the window has.
>
> type Window is ...;
> function Get_Border_Type (X : Window) return ... is abstract;
>
> type Dialog_Frame is new Window with private;
> function Get_Border_Type (X : Dialog_Frame return ...;

This doesn't begin to make sense. The object hasn't even found out what it's
border it (because it hasn't been constructed), and you want to ask what it
is?

Dispatching in a constructor is a bug, period. It's unfortunate that Ada
can't detect it (and I'm unconvinced that an implementable runtime check
could be made without distributed overhead). But there are a lot of bugs
that Ada doesn't try to detect (uninitialized components, for instance), so
I can't get that excited about this one.

                       Randy.