Re: [boost] [MPL.Math] Updated version now available

From: Andy Little (andy_at_[hidden])
Date: 2005-12-28 13:54:22

Hi Cromwell,

> "Cromwell Enage"  wrote
> Issues addressed:
>
> *  All metafunctions that can be instantiated in user
> code have been registered with Boost.Typeof (see
> typeof.cpp for a test case).  Registration of each
> metafunction occurs at the end of the header file in
> which the metafunction is declared, as per the "don't
> pay for what you don't use" policy.

Thats great and suits me, but I was wondering whether it might be better to
really make this optional, either by  looking for  a macro
BOOST_TYPEOF_PLEASE_REGISTER_MY_INCLUDED_TYPES (or whatever name) or by putting
the typeof stuff in a separate include file. Point is that on some compilers
where there is no inbuilt typeof, then Boost.Typeof causes a big slow down in
compile-performance. AFAIK this happens in VC8, though I havent tried this
compiler myself so I'm only guessing

> *  The BOOST_MPL_AUX_TYPEOF_REGISTER_TYPE_C macro,
> defined in
> <boost/mpl/aux_/typeof/register_type_c.hpp>, enables
> one to register metafunctions that have the following
> form:
>
> template <
>   typename ValueType
>  , ValueType N1
>  , ValueType N2
>  , ...
> >
> struct metafunction
> {
>     ...
> };
>
> This macro is currently used to register rational_c,
> mixed_number_c, and complex_number_c; it is hoped that
> vector_c, list_c, range_c, and integral_c will also be
> registered by it.  (The _C suffix indicates that the
> macro is to be used to register types ending in _c.)

That looks useful ;-)

[..]

> *  In case no one has noticed--and judging from the
> contents of pqs3_0_0.zip, this seems to be the
> case--there is now a math::inverse metafunction, so
> you don't need to roll your own reciprocal<>.

I wonder who that could be ;-)...Whatever, I would question the name 'inverse'
to replace 'reciprocal', because it needs a function to take the inverse of,
whereas reciprocal is unequivocal:

http://www.mathnstuff.com/math/spoken/here/1words/r/r13.htm

http://www.mathleague.com/help/fractions/fractions.htm#reciprocal

http://mathworld.wolfram.com/InverseFunction.html

---------------------

FWIW I have  attached some other related functions that might be useful.

boost::mpl::math::is_positive<T> ,to go with  boost::mpl::math::is_negative<T>
boost::ml::math::is_rational_constant<T> , to go with
boost::mpl::is_integral_constant<T>
boost::mpl:rational_int<>
boost::mpl:rational_long<>

Let me know what you think . If you like them I'll write some tests for them.

----------------------

Finally regarding the boost::math::mpl::power function, I was told once upon a
time that the traditional way to do this in mpl would be  to call it just 'pow'
after the runtime version. FWIW

regards
Andy Little

begin 666 is_positive.hpp
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M/%0^( T*(" @(" @(" ^.CIT>7!E('1Y<&4[#0HC96YD:68-"B @(" @(" @
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`
end

begin 666 rational_int.hpp
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M1$5$,0T*(V1E9FEN92!"3T]35%]-4$Q?34%42%]2051)3TY!3%])3E1?2%!0
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`
end

begin 666 rational_long.hpp
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M541%1 T*(V1E9FEN92!"3T]35%]-4$Q?34%42%]2051)3TY!3%],3TY'7TA0
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!( ``
`
end

begin 666 is_rational_constant.hpp
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05%](4%!?24Y#3%5$140-"@``
`
end