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From: "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>
Subject: Re: Inherited Methods and such
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Date: Sat, 29 Sep 2007 22:35:04 +0200
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Date: 2007-09-29T22:35:05+02:00
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On Fri, 28 Sep 2007 13:44:32 -0700, Maciej Sobczak wrote:

> On 28 Wrz, 21:42, Robert A Duff <bobd...@shell01.TheWorld.com> wrote:
> 
>> Here's an example.  What do you think?
> 
> Perfect! I wasn't aware of the possibility to use return to achieve
> this "progressive" construction process.

It is not return, the job is done by extension aggregates, these are Ada 95
by the way. C++'s

   Derived () : Base (), Component () {}

is equivalent to Ada's

   Derived'(Base with Component);

What Ada 2005 return adds, is a non-empty body of, i.e. the stuff between
{...} is do ... end return;

Then Ada 2005 allowed aggregates for limited types.

> I knew this form of return, but not the gory details of how tags are
> assigned.

The tag is set to reflect the object's type, what did you expect? (:-)) But
note, nothing is mutating in the example.

>> Do you revise your opinion that
>> Ada doesn't properly support constructors?
> 
> Yes, this example is convincing.

No, it is not. Because aggregate is not a replacement for user-defined
constructors.

1. It breaks encapsulation as you should make the record nature of type
public.

2. The base type cannot enforce vital construction code, when records are
exposed.

3. Nothing can be done for destructors.

4. Dispatch upon construction completion and before destruction beginning
is still impossible.

-- 
Regards,
Dmitry A. Kazakov
http://www.dmitry-kazakov.de