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From: Robert A Duff <bobduff@shell01.TheWorld.com>
Newsgroups: comp.lang.ada
Subject: Re: What would you like in Ada202X?
Date: Sun, 29 Apr 2012 15:04:34 -0400
Organization: The World Public Access UNIX, Brookline, MA
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Date: 2012-04-29T15:04:34-04:00
List-Id: <comp.lang.ada>

okellogg@users.sourceforge.net writes:

> Could you elaborate?

package P is
    package Q is
    private
    end Q;
private
end P;

package body P is
    package body Q is
    end Q;
end P;

In the above nested case:
P spec can see things in Q spec (imagine all sorts of declarations
 at various places above).
Private part of Q cannot see things in private part of P.
Nobody can say "with P.Q;".
If you say "with P;" you can automatically see Q.
Q cannot have its own with clauses.
The one you mentioned: you can't have a child "package P.Q.R is".
Q spec is elaborated in the middle of elaborating P spec,
 and similarly for the bodies.
Etc.

If we transform that structure into child packages:

package P is
private
end P;

package P.Q is
private
end P.Q;

package body P is
end P;

package body P.Q is
end P.Q;

Now every statement I made above about the nested case
is no longer true.  I don't like that.  I think the semantics
of the two above structures should be identical.  Unfortunately,
that was impossible, because child packages were added later,
and we couldn't change nested packages in any incompatible ways.

- Bob