From: Dean Foster (foster_at_[hidden])
Date: 2001-10-01 16:26:08
> What about assigning a different prime number to each dimension, and
> representing multiplication of units as multiplication of the associated
This would be great espicially if we could work mod-a-prime. Using
the GCD I think we can find the multiplicative inverse mod-a-prime.
Then division can be represented also. I don't think you get unique
factorizations when working mod-a-prime. So it still only provides
limited protection. But good enough to prove that most illegal
conversions would be caught with high probability.
> It also solves the decomposition problem (extracting the basic units and
> their exponents from a composite unit), which I suspect may be a
> showstopper for your addition-of-hash-values approach.
I wasn't planning on providing any way of extracting basic units from
the hash values. Should these be desired, probably a trait class
could be added to compute them. But I don't think it is actually
important to be able to do. These ARE compile time classes, so it
isn't as if we need to dynamically figure out the units.
Dean Foster dean_at_[hidden]
Statistics, Wharton, U. Penn 215 898 8233
Philadelphia PA 19104-6302 http://diskworld.wharton.upenn.edu
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