Re: Visibility of Indexing aspects

[Jere <jhb.chat@gmail.com>]

On Saturday, July 14, 2018 at 1:04:49 PM UTC-4, Shark8 wrote:
> On Saturday, July 14, 2018 at 8:18:38 AM UTC-6, Jere wrote:
> > I was going through an Ada library and noticed that they
> > were able to add an indexing aspect to a type in the private
> > section of a package but have the indexing work for types
> > declared using the public view of the type.  It's a neat feature,
> > but I wasn't sure if this was intentional or a GNAT bug?
> > I searched through sections 13.1 and 4.1.6 of the RM, but no
> > mention that I could find of the private/public requirements
> > for the Variable_Indexing and Constant_Indexing aspects.
> > 
> > Is there something I missed in the RM, is this a GNAT bug, or
> > something else?
> 
> I'm not sure what your problem is; it's perfectly fine to attach the predicate in the Private section:

I have no problem with it per say, but it runs contrary to how I
have experienced Ada so far, so I wanted to make sure before I
make use of it that it isn't a compiler bug.  This marks the first
time I have ever encountered a situation where the client of a
package can leverage functions from the private part of a package.

In my example, I expected that client had no access to any functionality
of the Container type because the public specification for it was:

    package Containers is

      type Container is private;
     
    private 

There was no mention of being able to index the type (publicly), so it
surprised me that a client using the package could call the index
operation.  If it was intentional, then that was fine, I just wanted to
know because I couldn't find anything in the RM that forbid it, but I 
might have missed something.