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From: Robert A Duff <bobduff@shell01.TheWorld.com>
Newsgroups: comp.lang.ada
Subject: Re: memory management in Ada: tedious without GC?
Date: Fri, 23 May 2008 19:03:28 -0400
Organization: The World Public Access UNIX, Brookline, MA
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Date: 2008-05-23T19:03:28-04:00
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Matthew Heaney <mheaney@on2.com> writes:

> On May 19, 4:35�am, Maciej Sobczak <see.my.homep...@gmail.com> wrote:
>>
>> How would you use this strategy to make a controlled stream (derived
>> from Root_Stream_Type)?
>
> package P is
>    type T is new Root_Stream_Type with private;
>    procedure Op (O : not null access T);  -- or whatever
> private
>    type Control_Type (O : not null access T) is
>      new Limited_Controlled with null record;
>
>    -- override Init and Final as req'd
>
>    type T is new Root_Stream_Type with record
>       Control : Control_Type (T'Access);
>       -- other components as req'd
>    end record;
> end P;

Yes, but this idiom is needed only when the Finalize of the derived type
needs to do something with the components of the parent type.  I think
that's unusual.  The more common thing is to extend a type with some
controlled components -- each component cleans up itself.  So you don't
normally need that pointer-to-containing-object.

By the way, O is a horrible name!

- Bob