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Subject: Re: [boost] Boost.Math and Math Constants
From: Jeffrey Lee Hellrung, Jr. (jeffrey.hellrung_at_[hidden])
Date: 20111207 11:30:32
On Wed, Dec 7, 2011 at 7:33 AM, Paul A. Bristow <pbristow_at_[hidden]>wrote:
> Boost.Math has always had an inconspicuous collection of useful math
> constants, mainly those that
> are used internally.
>
> The presentation of these was as a functiontemplate, called for example,
> as pi<double>().
>
> using namespace boost::math::constants;
> return pi<Real>() * r * r;
>
> This leads to some rather ugly equations and is most unpopular with
> scientific and engineering
> users.
>
> John Maddock has now added a new cunning feature that allows the vast
> majority of users who just
> want a builtin double to get the constants quickly as plain variables. So
> in nontemplate code,
> users can write
>
> using boost::math::double_constants;
> double area = pi * r * r;
>
> and users can read the equations easily.
>
> (Float and long double are similarly available in their own namespaces).
>
It seems like this isn't a huge improvement over
double const pi = boost::math::constants::pi< double >();
double area = pi * r * r;
...except when one wishes to use several constants (but I wouldn't think
that would be all that common...).
The original mechanism which can be used for higher multiprecision
> userdefined floatingpoint types
> appears unchanged but has been improved to work better with UDTs and high
> precision types.
>
> Some draft detailed docs about just these new proposals are at
>
>
> http://boostsandbox.sourceforge.net/libs/math_constants/doc/html/index.html
>
> We would like to be sure that
>
> 1 This additional mechanism of presenting constants is acceptable.
>
> 2 It is acceptable to add more constants (current new list is about 60
> constants).
>
> Are there important constants that you think we have missed?
>
> Do we need a minireview?
>
> Other views?
>
> Paul
>
> PS
>
> 1 Are there important constants that you think we have missed?
>
> 2 Please tell me of mistakes and typos in the draft docs.
>
I'll probably look over the draft docs when I get a chance.
 Jeff
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