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From: Andy Little (andy_at_[hidden])
Date: 2005-11-21 16:20:08

"Matt Calabrese" wrote
> Yup, it's still in the works. I'm currently in the process of switching over
> to using Eric Niebler's Proto library internally for dealing with expression
> templates (a sublibrary which was used in xpressive), as opposed to the
> bare-bones expression templates I was developing.

It will be interesting to see this in action! I have my doubts about coupling it
too closely to the units library, but I am happy to be proved wrong!

> As a side note, if any other unit library developers are interested (or
> anyone else), I recently made a simple metafunction for yielding integral
> and floating point promotions (4.5 and 4.6), as well as a binary
> metafunction for yielding the type after usual arithmetic conversions (5p9),

It might be as well to note that this functionality is provided by Boost.Typeof,
however Boost.Typeof can cause very slow compile times. (I hope that Arkadiy
Vertleyb and Peder Holt dont take unkindly to that remark!) Because of this my
approach is to provide various metafunctions for providing the result type of
operations internally in pqs units library, meanwhile registering required types
with Boost.Typeof for compatibility with other libraries.

I'm not sure how anyone else feels about this, but if the metafunctions (
currently I call them binary_operation, unary_operation and arithmetic_promote)
are still required( due to slow compile time of Typeof) then It would be useful
to give these functions the same name across libraries.

Andy Little

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