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From: Jeff Garland (jeff_at_[hidden])
Date: 2005-10-12 08:05:13

On Mon, 10 Oct 2005 23:22:24 -0400, Deane Yang wrote
> Jeff Garland wrote:
> >
> > Wow, that's amazing. Replace quantity_vector with time_duration and
> > quantity_point with time_point and you have the core concepts behind
> > date-time. And the 32 versus zero -- seems an awful lot like an epoch_time
> > adjustment. So I suppose I'm saying I believe there is something fundamental
> > here :-)
> >
> Yes, there is.
> If you dig back in the archives, I tried to explain it all before,
> but obviously not very well. Suffice to say that a "time point" and
> a "point quantity" are the same type of thing and that the
> difference between any two such things is a "vector quantity" or
> equivalently a "time_duration".
> Mathematicians have identified the common abstract concepts
> underlying these things, and I went on and on about this earlier.
> But I think I'm going to resist reviving all that, because I don't
> think it's particularly helpful. I like Matt's terminology, because
> it seems to be more meaningful for everyone.

Sorry if I missed or didn't respond to your comments the first time. However,
I now have reasons to be more interested in the theoretical foundations.
Specifically, the LWG committee is rightly an intense group that needs to
ensure the quality and correctness of things that get added to the standard --
having additional theoretical foundations for the date-time concepts can't
hurt. Any chance you can point me to some sort of references (preferably
readable to folks that have only taken ~15 college math courses ;-)



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