Re: Common ancestor (visibility rules)

[steve.folly@rdel.co.uk (Steve Folly)]

On Tue, 28 Mar 2000 08:47:22 GMT, dmitry6243@my-deja.com did clatter that
keyboard and type:

>Hello!
>
>Perhaps I've missed something, but it seems that compilation units
>(except for library ones) do not have common ancestor. Here is a simple
>example to highlight the problem:
>------------------- a.ads
>package A is
>   procedure Foo;
>end A;
>------------------- b.ads
>package B is
>   procedure A;
>end B;
>------------------- b.adb
>package body B is
>   procedure A is separate;
>end B;
>------------------- b-a.adb
>with A;
>separate (B)
>procedure A is
>begin
>   A.Foo; -- Error!
>end A;
>
>Now there is no way to use A.Foo in B.A, because B.A hides A. The
>problem could be easily solved if all compilation unit had have a common
>ancestor package, say "Root". Then package A could be specified as
>Root.A and A's Foo as Root.A.Foo. Interesting is that C++ has this
>feature.
>

Well, the Ada95 team beat you to it, 10.1.1(1) of the LRM states:

"A library_item is a compilation unit that is the declaration, body, or renaming
of a library unit. Each library unit (except Standard) has a parent unit, which
is a library package or generic library package. A library unit is a child of
its parent unit. The root library units are the children of the predefined
library package Standard. "

Which, in layman's terms means any specific non-child package is implicitly a
child of package Standard.

So to get your separate A procedure to compile you need to fully qualify
A.Foo as Standard.A.Foo.


Hope that helps.
Steve Folly.