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From: Phil Richards (news_at_[hidden])
Date: 2005-10-21 05:12:20

On 2005-10-20, Matthias Troyer <troyer_at_[hidden]> wrote:
> A general purpose system, that could be used to implement SI or
> totally alien unit systems --- even more alien than the US one :-)
> --- would be the best way to go. An SI unit system could then be
> easily built on top of it.

Well, SI wasn't a fundamental part of what I did - SI was an
instantiation of a set of dimensions and units like so:
struct SI : physical7_system<u::meter, ...> {};

You can define any system you like, and instantiate with any
set of units you like. The point is, however, that SI
(being derived from physical7_system<>) is only unit convertible
to other instantiations of physical7_system.

For example, it can convert to things from
    struct Imperial : physical7_system<u::foot, ...> {};
but not
    struct USDollar : currency_system<u::dollar>
    struct UKPound : currency_system<u::sterling>
(which USDollar and UKPound are inter-convertible)

I'm obviously missing something. I can't see what more flexibility
is needed :-(


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