Package names & visibility

Package names & visibility

[John Woodruff B481]

I find myself puzzled by some consequence of a visibility rule in naming
packages, and I wonder if I need to reconsider my plan for making up
these names (of if there is a simple re-phrasing that I should know).

In very simple form, I have a package specification that declares some
type (and other declarations as well of course).

Let's say my system will have motors, sensors, switches, etc.  So I will
operate my motors with a package such as

package Motor is
   type  Yes_It_Is  is new Integer ;
end Motor ;

But I need other information in addition to the direct control that I'll
implement in the package Motor.  Therefore I thought I'd make a family
of packages to hold info about motors and sensors etc

package Info_About is
  -- a package that will have children
end Info_about ;

My intention is to have children packages carry different sorts of
info_about;  So there will be a package

with Motor ;
package Info_About.Motor is
  A  : Motor.Yes_It_Is ;
  --  (I'm not *really* going to declare a visible object!)
end ;

My thinking was that Info_about.Motor will hold some data values (which
are of types defined by the Motor package).

But I can't seem to refer to the type Yes_It_Is!  My friend Gnat tells me
info_about-motor.ads:3:13: "Yes_It_Is" not declared in "Motor"

This message clearly states that the visibility of info_about.motor is
hiding the package Motor where the type is declared.

Please suggest a way that I can refer to the identifiers that are
declared in Motor from inside the package Info_about.motor.   Thx!

--
John Woodruff	                                          N I F   \ ^ /
Lawrence Livermore National Lab                         =====---- < 0 >
510 422 4661                                                      / v \

Re: Package names & visibility

[Jon S Anthony]

In article <udspb9atdo.fsf@calaveras.llnl.gov> woodruff@calaveras.llnl.gov (John Woodruff B481) writes:

> with Motor ;
> package Info_About.Motor is
>   A  : Motor.Yes_It_Is ;
>   --  (I'm not *really* going to declare a visible object!)
> end ;
> 
> My thinking was that Info_about.Motor will hold some data values (which
> are of types defined by the Motor package).
> 
> But I can't seem to refer to the type Yes_It_Is!  My friend Gnat tells me
> info_about-motor.ads:3:13: "Yes_It_Is" not declared in "Motor"
> 
> This message clearly states that the visibility of info_about.motor is
> hiding the package Motor where the type is declared.
> 
> Please suggest a way that I can refer to the identifiers that are
> declared in Motor from inside the package Info_about.motor.   Thx!

Maybe this should (is?) in the FAQ.  Two ways:

1. Everything is rooted at Standard, so refer to the "outside" Motor as
Standard.Motor:   A : Standard.Motor.Yes_It_Is;

2. Provide a renaming for "outside" Motor before entering scope of child
Motor.  Maybe in Info_About or at library level.

Option #1 is really the preferred IMO.

/Jon
-- 
Jon Anthony
Organon Motives, Inc.
1 Williston Road, Suite 4
Belmont, MA 02178

617.484.3383
jsa@organon.com

Re: Package names & visibility

[Robert A Duff]

In article <JSA.96Jul5140611@organon.com>,
Jon S Anthony <jsa@organon.com> wrote:
...[two reasonable solutions omitted]
>Option #1 is really the preferred IMO.

My preference is to avoid using the same name for two different
packages, especially when those packages reference each other, or are
used together.

- Bob

Re: Package names & visibility

[Jon S Anthony]

In article <Du4v94.8CK@world.std.com> bobduff@world.std.com (Robert A Duff) writes:

> In article <JSA.96Jul5140611@organon.com>,
> Jon S Anthony <jsa@organon.com> wrote:
> ...[two reasonable solutions omitted]
> >Option #1 is really the preferred IMO.
> 
> My preference is to avoid using the same name for two different
> packages, especially when those packages reference each other, or are
> used together.
> 
> - Bob

Oh, you mean the _really_ really preferred approach!

/Jon
-- 
Jon Anthony
Organon Motives, Inc.
1 Williston Road, Suite 4
Belmont, MA 02178

617.484.3383
jsa@organon.com