Re: Private Children

[Tucker Taft <stt@averstar.com>]

Ted Dennison wrote:
> 
> In article <m3bteacxb8.fsf@mheaney.ni.net>,
>   Matthew Heaney <matthew_heaney@acm.org> wrote:
> > Can a public child package with its private sibling?
> >
> 
> Almost exactly one month ago, I posted the exact same question.
> Go to deja.com and search for a thread titled "Children of private
> compilation units" to see the discussion.
> 
> As I remember, it went something like this: Gnat doesn't accept it, and
> Robert Dewar says its not legal Ada. ObjectAda and GreenHills do accept
> it, and Tucker Taft says it *is* legal Ada. I offered to send in a bug
> report to the appropriate vendor, if a consensus could be reached on
> which one was in error. Currenly there appears to be no such consensus.

No, this was a different issue.  It had to do with whether
a specless subprogram was considered a spec or a body.  Bodies
are allowed to "with" private siblings, specs are not.  In this
case, the ultimate consensus position, based on AARM readings,
is that a specless subprogram is treated like a "spec" for the
purposes of this rule, and may not "with" a private sibling.

To answer the question posed by this new question, the answer
given by Dale was correct, that private children provide "compilation
privacy."  If you want to allow something to be "with"ed by public
children's specs, but contain content that is only visible to
the private part of the child's spec, the following idiom works:

   package Mostly_Private is
   private
       ... -- Declarations visible only in private part of other public
       ...  -- siblings
   end Mostly_Private;

That is, put the entire set of declarations in the private part
of a public child.


> T.E.D.

-- 
-Tucker Taft   stt@averstar.com   http://www.averstar.com/~stt/
Technical Director, Distributed IT Solutions  (www.averstar.com/tools)
AverStar (formerly Intermetrics, Inc.)   Burlington, MA  USA