RE: [vhdl-200x-ft] Question on Type and Package Generics

Quoting Peter Ashenden <peter@ashenden.com.au>:

> Tristan,
>
> I suspect you may have missed out on some of the history. My original
> proposal was based on Ada generics, and included many of the same features
> for specifying kinds of formal types in generic lists.
Thank you for the historical aspect.

> However, we decided
> to limit formal generic types in the current revision to be essentially like
> Ada "is private" generic types.
I have one comment.
Unless I miss some point, there is no formal subprogram in the generic list.
I really think this is a mistake. Generic will not be powerful enough to
create a generic sort subprogram!
Furthermore, the analyzer need to make checks during the analysis of a generic
package/subprogram.

> The main reason for doing so is that we
> plan to develop object-oriented extensions to the type system in a later
> revision. Whatever we do with generic types needs to be compatible with the
> extensions to the type system. I've proposed a minimal form of generic
> types that I believe will not constrain the type-system extensions.
I don't follow. Generics and type extension are really orthogonal features.

> Ada-95 introduced object orientation through extensions to packages and to
> types and operations defined in packages.
I don't agree on the last point: extensions to packages (aka child packages)
is not object orientation.

> While we could do similarly, we
> need to recognize the VHDL's protected types are closely aligned to class
> definitions in OO languages.
Again, I don't really see the point. Is there any reference ?
Protected types are not OO. No polymorphism, no type extensions.

> There is a preference among WG members to
> develop OO features based on extending protected types rather than by
> following the Ada-95 approach.
> Either way, this will take some effort to
> develop, hence it's deferred to the next revision. (Which, by the way, need
> not be as far away as 5 years from the current rev)
>
> I hope this clarifies the direction being proposed.
Sure, it does. Again thank you for the historical view.
However, I really think the generics as currently proposed are not powerful
enough to be useful.

Tristan.
Received on Fri Dec 24 05:55:54 2004