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From: Niklas Holsti <niklas.holsti@tidorum.invalid>
Newsgroups: comp.lang.ada
Subject: Re: Quick question regarding limited type return syntax
Date: Mon, 04 Aug 2014 20:49:06 +0300
Organization: Tidorum Ltd
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Xref: news.eternal-september.org comp.lang.ada:21449
Date: 2014-08-04T20:49:06+03:00
List-Id: <comp.lang.ada>

On 14-08-04 14:39 , Peter Chapin wrote:
> On 2014-08-04 06:42, G.B. wrote:
> 
>>   C++, I think, lets "this" stand for the type at the current "level"
>> during construction, so there is no dispatching to lower levels IIUC;
>> however, Stroustrup mentions some pointer tricks that let the
>> programmer circumvent the restriction.
> 
> It's true that in C++ dynamic dispatch is "turned off" during the
> execution of a constructor (and destructor). This is precisely to
> prevent the use of an uninitialized object when a base subobject is
> being constructed (or destroyed). It's a feature! It seems to me that
> circumventing it would be like circumventing the type system.

It is a circumvention of the C++ type (or class) system because it has
been made so intentionally, by the logical meaning given to constructors
in the language.

> You might
> be able to do it but... it would be a big warning flag that something is
> wrong.

"Wrong" from the point of view of the C++ object philosophy, yes, but
IMO not necessarily wrong for the Ada object philosophy, where the
Initialize primitive does not have such a strong predefined meaning
(which is just what Dmitry complains about).

-- 
Niklas Holsti
Tidorum Ltd
niklas holsti tidorum fi
      .      @       .