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From: "Randy Brukardt" <randy@rrsoftware.com>
Newsgroups: comp.lang.ada
Subject: Re: Ada 95 and Class attribute for none-tagged incomplete type
Date: Thu, 13 Aug 2009 23:21:39 -0500
Organization: Jacob Sparre Andersen
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Date: 2009-08-13T23:21:39-05:00
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"Robert A Duff" <bobduff@shell01.TheWorld.com> wrote in message 
news:wcc7hx7onv6.fsf@shell01.TheWorld.com...
...
> The purpose of the rule is so you can create recursive types, as in:
>
> package P is
>   type Priv is private;
> private
>   type Acc is access all Priv'Class; -- Legal!!!!!!
>   type Priv is tagged
>        record
>            Next : Acc;
>            ... --etc.
>        end record;
> end P;
>
> without exposing the taggedness to clients.  Note that Acc is in the
> private part, so there's no privacy-breaking going on.

Another example of why you ought to come to meetings more often. I don't 
recall anyone figuring that out per-se (although it is obvious that you can 
use it in this way). All this special rule eliminates is the need to declare 
an incomplete type in this one unusual case (the private type in cases like 
this is best declared as tagged, so this shouldn't happen very often). Seems 
like a pile of work for an implementation and for the language just to 
eliminate one line in a private part.

                                            Randy.