Re: Visibility of private packages??

[john.nospam@nospamassen.nospamdemon.co.uk (John McCabe)]

On Tue, 30 Jul 2002 15:23:40 -0600, "Peter Coventry"
<Peter.Coventry@gdcanada.com> wrote:

>I am trying to get my head around the visibility rules applicable to private
>packages.
>
>If I have the following package hierarchy:
>
>           A
>        /      \
>     A.B1   A.B2
>    /
> A.B1.C1
>
>A.B1 contains the interface that I wish to export to clients (i.e a type
>plus routines for client manipulation).
>A.B1.C1 contains additional routines for the type not meant for client use.
>A.B2 contains some inner workings, that need to use the additional routines
>in A.B1.C1.
>
>I want to make A.B1.C1 a private package to stop it from being misused by
>clients, however the compiler disallows it, citing RM 10.1.2(8):
>
>" If a with_clause of a given compilation_unit mentions a private child of
>some library unit, then the given compilation_unit shall be either the
>declaration of a private descendant of that library unit or the body or
>subunit of a (public or private) descendant of that library unit."
>
>Does this mean that if A.B1.C1 is private, it can only be withed by the
>bodies of A.B1 and other descendants of A.B1, and specs of private packages
>of descendants of A.B1?
>
>If this is the case, how could I structure things to give the desired
>effect?

As far as I remember, "Ada As A Second Language" by Norman Cohen has
some reasonable stuff on private child packages so it might be worth
looking there.

If the type you are referring to is tagged, would it help to declare
the A.B1.C1 facilities as dispatching operations in the private part
of A?