From: Stewart, Robert (stewart_at_[hidden])
Date: 2002-03-05 13:11:26
From: Dietmar Kuehl [mailto:dietmar_kuehl_at_[hidden]]
> If I can convince others, too, that property maps are the way
> to go (the
> first attempt into this direction was an article in C++ Report about
> "Data Access Templates"...) it will become *the* approach and it would
> be in no way obscure. I discussed this issue with several committee
> members already but I think either they weren't really interested or
> didn't understand the issue or both. Some years back I discussed the
> property map approach with Alexander Stepanov (at this time they were
> still under the name "Data Accessors") and a lot of time to
> convince him
> of the usefulness of this abstraction - and we could only agree on the
> distinction between between reads and writes being
> important... There is
> *more* to this simple abstraction. Much more!
Given the audience you've had when trying to explain property maps, and
given your current struggle, I have to wonder whether there's a problem with
the property maps idea or if it's just your ability to explain them.
I've not looked at property maps, but I've gleaned at least some aspect of
them from your posts in this thread: They are some sort of collection --
runtime or compile-time I don't know -- of indexed properties (or
attributes). Apparently, the advantage is that the collection can be
extended, to include things not originally conceived, without changing any
structures, adding members functions, etc. I gather that one must create a
type to represent a property, but I don't know how such properties are added
to or accessed from the property maps.
Anyway, property maps sound interesting, but if they are so different from
the "normal" ways of doing things in C++, I wonder whether they will
interoperate with the "normal" ways or be relegated to obscure libraries and
niches of users. I also wonder whether they will gain acceptance as yet
another significant, yet orthogonal paradigm supported by C++, like
procedural, OO, and generic programming.
Given the foregoing, I find myself agreeing with Beman and Jeff Garland that
the fundamental attributes should be accessible the "normal" way, possibly
duplicated by property map access. Then, the less standardized,
platform-specific and user-defined properties could be managed by the
property map mechanism.
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