questions about "Programming by Extension" article in Adapower

questions about "Programming by Extension" article in Adapower

[Dan Raviv]

The link to the article:
http://www.adapower.com/articles/extension.html

As far as i understand the article, it provides a way to use
polymorphism for ADOs (whereas it is usually used with ADTs).

However, there are a few issues in the article which i do not feel
comfortable with.

First of all, shouldn't the FLAG type in GENERIC_INTERFACE be a private
type? And also, an abstract one?

Also, shouldn't the DATA parameter of the GET procedure be an out
parameter?

Finally, even though we assume that the FLAG type in GENERIC_INTERFACE
and the FLAG types derived from it will never contain any data,
shouldn't we still define them as private (or with private) and use the
null record in the private part? There is always a chance that we MIGHT
want to add some fields to the flags... Even though it is unlikely. And
even if there is no such chance, i think the flags implementation
should be hidden in the private part.

You thoughts? :)


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