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From: "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>
Newsgroups: comp.lang.ada
Subject: Re: Taking 'Access of single task/protected object
Date: Thu, 7 Jan 2016 18:30:54 +0100
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Date: 2016-01-07T18:30:54+01:00
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On 2016-01-07 17:18, G.B. wrote:
> It seems impossible to take the 'Access (or 'Unchecked_Access)
> of a single task object, since it cannot be made aliased.
> And, I guess, as it is not of a named type, so that there
> is no way to express even an anonymous access type.
>
> This is, I think, the crucial bit of a question (34540199)
> asked at stackoverflow. (The example uses some listener pattern
> which looks like Java written in Ada, but that's not why I'm
> asking.)
>
>    task Single is
>       entry Something;
>    end Single;
>
>    ...some_context (access_discriminant => Single'Access)...

It does not make sense because you cannot declare a discriminant without 
mentioning the task type. Therefore it cannot be anonymous.

[ I leave aside the question if anonymous task/protected object types 
should be allowed:

    type T (Reference : access task is entry Something; end) is ...

Ada's degradation has not reached this low, yet? ]

> So, suppose some_context requires indirect access to a single
> task object, i.e., to one of an anonymous task type.
 > Is there a preferred solution to single-task vs. multiple
 > references?

    task type Single is
       entry Something;
    end Single;
    ...
    Object : aliased Single;
    ...
    type T (Reference : not null access Single) is ...

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