Re: Ada Annoyances

["Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>]

On 2017-06-25 13:33, Maciej Sobczak wrote:
> 
>> For T substitute Abstract_TCP_Server. For Bar substitute
>> Get_IP_Address_To_Listen.
> 
> And I still don't see any benefit.

It is frequently used design pattern to leave some parts of construction 
used by the parent type to the children.

> Can you explain what
> functionality is available in this scheme (and that is not available
> currently in Ada  or C++)?

In Ada one uses a class-wide operation dispatching to the construction 
call (Get_IP_Address_To_Listen) and a comment that Initialize must call 
it or else the parent's Initialize (which calls it too) if overridden. 
Since Ada's Initialize is called late it is OK to dispatch from there. 
C++ which calls its initializers early. The point is that construction 
requires both early (type-specific) and late (class-wide) initializers.

[...]
> Most importantly, useObject does not know that it gets called from
> constructors, because it might be called from any other context as well.
> It might be even in a different translation unit.
> 
> This shows that dispatching is *not* "killed" and whatever
> environment  heating takes place,

I don't see how it shows that, or anything.

> I understand that it is beyond the threshold of humiliation for a
> die-hard Ada programmer, but I personally don't find it difficult to
> admit that this is the part that C++ got right.

The only right thing are type-specific constructors. Everything else in 
the C++ construction model is wrong. And it is not in Ada's favor. Ada's 
user-construction model is wrong too.

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