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From: Niklas Holsti <niklas.holsti@tidorum.invalid>
Newsgroups: comp.lang.ada
Subject: Re: Ada Alternatives to Unrestricted_Access
Date: Tue, 13 Mar 2018 09:46:14 +0200
Organization: Tidorum Ltd
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Xref: reader02.eternal-september.org comp.lang.ada:50953
Date: 2018-03-13T09:46:14+02:00
List-Id: <comp.lang.ada>

On 18-03-13 01:30 , Randy Brukardt wrote:

> One easy way to get a rewritable reference of a controlled type is to save
> it in the Initialize routine (note that the argument of Initialize is "in
> out"). So you could have something like:
>
>     type Container is tagged;
>     type Acc_Container is access all Container;
>     type Container is new Controlled with record
>         Self : Acc_Container;
>     end record;
>
>     procedure Initialize (Obj : in out Container) is
>     begin
>          Obj.Self := Obj'Access;
>     end Initialize;
>
> And then you can use "Self" anytime you need to write the container object.

A note, just to remind myself and others: for a non-limited Container 
type this "Self" component must also be updated (in fact restored to its 
Initialized value) in the Adjust operation. Otherwise, if A and B are 
Container objects, after A := B the component A.Self would access B.

-- 
Niklas Holsti
Tidorum Ltd
niklas holsti tidorum fi
       .      @       .