Re: Assistance on extending a private record from a private record with a generic attribute...

[Christopher Campise <crc@amherst.com>]

Thanks for your help, but with all due respect ,on Tucker's behalf, he did
point out that 'generic' is a reserved word in his reply to my inquiry.

But on another note, if I have a private record type extension from my generic
package and I want to extend THIS record to create a 3 level inheritance tree:

My generic class
****
generic
   type Value_Class is tagged private;

package My_Generic is
   type Class is tagged private;
    ...

private
   type Class is tagged
      record
         Some_Value : Value_Class;
      end record;
end My_Generic;
***

***
with my_generic;

generic
   with package My_Class is new My_Generic(<>);

package My_Class is
   type Class is new My_Class.Class with private;
...

private
   type Class is new My_Class.Class with
      record
         Value1 : Integer;
         Value2 : Integer;
      end record;
end My_Class;

If I wanted to extend My_Class, would the following be acceptable?

***
with my_class;

package another_class is
   type Class is new my_Class.class with private;
...

private
   type class is new my_class with
      record
         another_value : Integer;
      end;
end another_class;

Please excuse my ignorance.  I'm fairly new to Ada95.

Anonymous wrote:

> <35364E81.94B51B0F@amherst.com>
>
> On Thu, 16 Apr 1998 21:26:10 GMT, stt@houdini.camb.inmet.com (Tucker
> Taft) wrote:
>
> > Christopher Campise (crc@amherst.com) wrote:
> >
> > : Ada95 on a Rational Apex compiler:
> > : I have a "superclass" with a private record consisiting of a generic
> > : type attribute.  I need to inherit this from within another package but
> > : am receiving compiler errors stating that "a record extension will be
> > : provided iff the parent record is tagged," (which it is).  Is this even
> > : legal?  I looked everywhere for examples and found none that relate to
> > : this, adahome.com, Programming in Ada95, Rendezvous with Ada95, plus
> > : other tutorials.  Any ideas?
> >
> > You cannot select items from a generic package.  You must
> > first instantiate the generic package, and select items from
> > the instance.
> >
> > : For example:
> >
> > : ***********
> > : generic
> > :    type Value_Class is private;
> >
> > : package Generic is
> > :    type Class is tagged private;
> > ...
>
> Surprisingly, even Tucker Taft did not point out that you cannot have a
> package named Generic. "generic" is a reserved word.
>
> Assuming that you change the name, perhaps to Generic_Class, then you
> still don't have a package, so you can't refer to its type Class. You
> need to instantiate the generic:
>
> package My_Class is new Generic_Class (Value_Class => My_Type);
>
> Now you have a package named My_Class, and may refer to My_Class.Class.
>
> Jeff Carter  PGP:1024/440FBE21
> My real e-mail address: ( carter @ innocon . com )
> "Son of a window-dresser."
> Monty Python & the Holy Grail
>
> Posted with Spam Hater - see
> http://www.compulink.co.uk/~net-services/spam/



--
Christopher Campise, Associate Engineer
Amherst Systems Inc.
30 Wilson Road
Buffalo, NY 14221
phone:  (716)631-0610 x384
E-Mail: crc@amherst.com
WWW: www.amherst.com