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From: Dmitry A. Kazakov <mailbox@dmitry-kazakov.de>
Newsgroups: comp.lang.ada
Subject: Re: Need advice re package organization.
Date: Thu, 31 Jul 2003 11:04:59 +0200
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Date: 2003-07-31T11:04:59+02:00
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On Wed, 30 Jul 2003 17:00:00 -0400, "Warren W. Gay VE3WWG"
<ve3wwg@cogeco.ca> wrote:

>Dmitry A. Kazakov wrote:

>> Such subroutines could be viewed as an
>> equivalent to C++'s "private methods". What Ada does not have are
>> private data members in C++ sense. So we have:
>> 
>> protected in C++ <--> private in Ada
>> private method <--> a subroutine in the body [a FAT plus to Ada ]
>> private member  <--> missing [a minus]
>
>I think you need to add a dimension to this "chart", because
>there are multiple (at least 2) views:
>
>   1. simple client view
>   2. a _normal_ child package view
>
>   (a _private_ child's view is the same I think, but if not, this
>    is a 3rd).
>
>The problem I am trying to address, is #2. The child package sees
>all, even when you don't want it to.

But if you do not want to see private things, then the package should
not be a child.

-----------------------------------------
However I should admit that there is a problem, not only in Ada, but
it other OO languages too. It is a "philosophic" problem:

"When implemening a method should I favour private or public
interface?"

Note that this problem exists even for a single package / class. Let I
have a public Getter for some hidden member, should I use it instead
of accessing the member directly implementing some other method?

There is no definite answer to this, but in what a language (Ada)
could help is in a clear separation of both.

As a raw idea, one could have public and private parts of the package
body. Or alternatively, one could have up to two bodies, private and
public:

package [private] body A is
   -- I see everything
   -- All dirty stuff goes here
end A;

package public body A is
   -- I see only the public part
   -- I need not review this body as long as the public part
   -- remains unchanged
end A;

---
Regards,
Dmitry Kazakov
www.dmitry-kazakov.de