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From: Robert A Duff <bobduff@shell01.TheWorld.com>
Newsgroups: comp.lang.ada
Subject: Re: Inherited Methods and such
Date: Fri, 28 Sep 2007 15:12:51 -0400
Organization: The World Public Access UNIX, Brookline, MA
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Date: 2007-09-28T15:12:51-04:00
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Maciej Sobczak <see.my.homepage@gmail.com> writes:

> On 27 Wrz, 15:39, Robert A Duff <bobd...@shell01.TheWorld.com> wrote:
>> But I find the C++ solution less than ideal -- the programmer might well
>> expect to dispatch to the deeper type, and be surprised when it doesn't.
>
> Of course. I can assure you that this question is quite regular and
> even has its own FAQ entry:
>
> http://www.parashift.com/c++-faq-lite/strange-inheritance.html#faq-23.5
>
>> Question: why do you want to dispatch at all during construction?
>
> I don't.

OK, good.  So neither C++ nor Ada is ideal here, because both allow
dispatching during construction.  (And for Initialize, Ada is arguably
worse than C++, since it allows dispatching to the deeper type.)

> Yes, but this was taken out of some fragment of this lengthy
> discussion. Registration requires that T'Class is available in the
> base type constructor.
>
> So - even if I don't need to dispatch, I might need T'Class.

Interesting.  I'm not sure what the best language design would be, for
this sort of thing.

>> In other words, would you be happy with a rule saying you can't dispatch
>> during construction?
>
> I would be perfectly fine with this rule, but having this rule *and*
> access to T'Class are not much compatible with each other.

Indeed.

>... How can you
> prevent me from dispatching if I already have T'Class? With runtime
> checks, perhaps?

In the Ada context, a run-time check is the only way I can think of.

- Bob