Re: Two ideas for the next Ada standard

[bobduff@world.std.com (Robert A Duff)]

In article <503sbo$j45@goanna.cs.rmit.edu.au>,
Dale Stanbrough  <dale@goanna.cs.rmit.EDU.AU> wrote:
>...and given someone has started this thread :-)
>
>I presume the occasional murmers of unhappiness about the lack of utility
>of private packages is due to the fact that they can't be 'with'ed by
>a public {package|subprogram} spec because of the possibility of 
>revealing private details (is this right?).

Perhaps people would be happier if they were called "body packages" -- a
private child of X is more like the body of X, than the private part of
X, in terms of visibility.  In any case, I'm pretty happy with the rules
as they are.

>If this is the case then could we have...
>
>
>	with private fred; -- this does not mean fred is private!
>	                   -- perhaps "private with fred;" would be
>	                   -- better?

Independent of the question of child packages, it is definitely an
annoyance that a with_clause has to go up at the top, when you really
only want it for the private part.  The mistake, I think, is that the
syntax requires with_clauses outside the unit -- it makes more sense to
me, to put them inside:

    package X is
        with Y;
        ...
    private
        with Z;
        ...
    end X;

But that ain't Ada.

It's interesting that during the Ada 9X design, somebody proposed the
exact same syntax you propose here, but with a totally different
meaning.  In particular, "with private Stuff;" would mean I can see the
private part of Stuff -- it was proposed as an *alternative* to child
units.

>	package mary is
>	
>		...
>	private
>		-- can only use resources from fred in
>		-- the private section, e.g. for renames,
>		-- type completions etc.
>	end mary;

>Gee, this is fun! :-).

Language design is a *lot* of fun.

- Bob