Re: Child Package Operator Visibility

[Robert A Duff <bobduff@shell01.TheWorld.com>]

Adam Beneschan <adam@irvine.com> writes:

> In fact, this sort of thing is an idiom I used to use a lot, before
> Ada 95 gave us "use type".

Me, too.

>...I would declare a package with the types I
> wanted to declare, and then define a nested package Operators which
> redefined all the operator symbols on those types using renaming, so
> that another package could say "use Pkg.Operators" without having to
> "use Pkg" which would make too much visible.

Nobody would type:

    function "+" (X, Y: T) return T renames Pkg."+";
    function "-" (X, Y: T) return T renames Pkg."-";
    ...

Instead, you type:

    function "+" (X, Y: T) return T renames Pkg."+";

Cut&paste, to get:

    function "+" (X, Y: T) return T renames Pkg."+";
    function "+" (X, Y: T) return T renames Pkg."+";
    ...

Then fix it up:

    function "+" (X, Y: T) return T renames Pkg."+";
    function "-" (X, Y: T) return T renames Pkg."+";
    ...

Oops.  Now you've got a nasty bug, which is hard to see.  ;-)

The problem is that you don't want to "rename" anything -- you want to
import it into a different scope with the _same_ name, and Ada's
renaming declaration is too powerful for that job.

- Bob