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From: "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>
Newsgroups: comp.lang.ada
Subject: Re: Controlled types as interfaces
Date: Wed, 20 Aug 2014 15:47:56 +0200
Organization: cbb software GmbH
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Date: 2014-08-20T15:47:56+02:00
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On Wed, 20 Aug 2014 15:49:36 +0300, Victor Porton wrote:

> Dmitry A. Kazakov wrote:
> 
>> On Wed, 20 Aug 2014 04:09:15 +0300, Victor Porton wrote:
>> 
>>> Victor Porton wrote:
>>>> I think in Ada 202X we can invent Limited_Controlled_Interface and
>>>> Controlled_Interface types derived from which could become controlled.
>> 
>> Yes, but that would be very complicated, because you could add an
>> interface very late, making a descendant of a non-controlled type
>> controlled.
>> 
>> A better solution would be fixing initialization (AKA constructors) and
>> leaving controlled kludge as is.
> 
> I don't see any reason not to make descendant of a non-controlled type 
> controlled.

I don't see why any type cannot have initialization hooks either.

> Let T is a non-controlled tagged type.
> 
> It descendant Q is like a record
> 
> record
>    Old: T;
>    Ext: Q1;
> end record;
> 
> (where Q1 is the difference of Q and T).
> 
> Q1 is controlled.
> 
> As there is no problem that this record becomes controlled, there are no 
> reason not to make Q controlled despite of T was non-controlled.

It depends on concrete implementations, e.g. some might require the type
tag being at the record's first address.

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