Re: Inherited Methods and such

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

On Sat, 29 Sep 2007 13:52:40 -0700, Maciej Sobczak wrote:

> On 29 Wrz, 22:35, "Dmitry A. Kazakov" <mail...@dmitry-kazakov.de>
> wrote:
> 
>> 1. It breaks encapsulation as you should make the record nature of type
>> public.
> 
> Why it would make any difference?
> The type is tagged and this is known. If it's tagged, then it has the
> record nature - no way and no reason to hide it.

It is a language fault that there are types which cannot be
user-constructed. The problem is that if you tried to fix the language, for
example by allowing a task object being shut down when finalized, you would
make them all records. Is it LISP or Ada?

>> 2. The base type cannot enforce vital construction code, when records are
>> exposed.
> 
> I don't understand this part.

If the object is just a record I can assemble it in any available way. And
there are many of them. You will have a difficult design problem to ensure
that all these ways do call your construction code. For example: 

Uninitialized base:

   X : Base;
begin
   return (X with ...) do ... end record;

Worked-around base:

   return (X'(Xs_Base with Something) with ...) do ... end record;

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

> Why?

It goes this way:

  return (Base with Mine) do My-take end record;

But the [class-wide] code to execute should be placed after "end record," 
IFF there is no following derived type under construction. Only compiler
magic can help here.

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