Re: OOD in Ada?

["Marin David Condic" <dont.bother.mcondic.auntie.spam@[acm.org>]

I'm not sure all the newsgroup data is getting through. I've outlined
basically that twice & maybe the OP isn't seeing it.

You can use child packages or non-child packages that inherit from some base
class. The important thing is that as long as the subclasses inherit from a
base class you can have an access value to anything within the class
heierarchy - hence classes "A" and "B" can have references to each other.

A good example of this is the XML DOM - You start with a base class called
"Node" which doesn't represent any actual elements in the DOM tree, but
defines some common characteristics. (Perfect case for an abstract class.)
All other elements of an XML document are represented as a derived class
from this base class. Since many of the XML document elements contain other
elements that might be composed of yet other elements of all sorts of types,
you need to have them able to hold references to each other but without the
"withing problem". The base class of type "Node" fixes this - you have an
access type that can reference anything of type Node'Class & then you're
stardust.

MDC
--
Marin David Condic
Senior Software Engineer
Pace Micro Technology Americas    www.pacemicro.com
Enabling the digital revolution
e-Mail:    marin.condic@pacemicro.com


"Hyman Rosen" <hyrosen@mail.com> wrote in message
news:Dl8S8.26239$cE5.16490@nwrddc02.gnilink.net...
>
> Keeping in mind that I don't know Ada, isn't this what child packages are
for?
> Declare the base expression and statement classes in a package, and put
each
> descendant in its own child package.
>