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[section:constants Numeric Constants]
[h4 Synopsis]
``
#include <boost/math/constants/constants.hpp>
``
namespace boost{ namespace math{ namespace constants{
template <class T> T pi();
template <class T> T root_pi();
template <class T> T root_half_pi();
template <class T> T root_two_pi();
template <class T> T root_ln_four();
template <class T> T e();
template <class T> T half();
template <class T> T euler();
template <class T> T root_two();
template <class T> T ln_two();
template <class T> T ln_ln_two();
template <class T> T third();
template <class T> T twothirds();
template <class T> T pi_minus_three();
template <class T> T four_minus_pi();
}}} // namespaces
[h4 Description]
The header `boost/math/constants/constants.hpp` contains some numeric constants
that we have found useful in the development of this library. New constants are
added on an ad-hoc basis based on need.
Usage is like this:
template <class T>
T circumference(T r)
{
return 2 * boost::math::constants::pi<T>() * r;
}
All the constants are accurate to at least the 34 decimal digits required for 128-bit
long doubles, and most are accurate to 100 digits or more when used with
a suitable arbitrary precision type.
The following table summarises the constants we have at present:
[table
[[Constant][Meaning][Value]]
[[pi][[pi]][3.1415926535897932384...]]
[[root_pi][[radic][pi]][1.772453850905516027...]]
[[root_half_pi][[radic]([pi]/2)][1.253314137315500251...]]
[[root_two_pi][[radic](2*[pi])][2.506628274631000502...]]
[[root_ln_four][[radic](ln(4))][1.17741002251547469...]]
[[e][['e]][2.71828182845904523536...]]
[[half][0.5][0.5]]
[[euler][Euler's constant][0.577215664901532860606]]
[[root_two][[radic]2][1.4142135623730950488...]]
[[ln_two][ln(2)][0.6931471805599453094...]]
[[ln_ln_two][ln(ln(2))][-0.3665129205816643...]]
[[third][1/3][0.333333333333333333...]]
[[twothirds][2/3][0.666666666666666666...]]
[[pi_minus_three][[pi]-3][0.14159265358979323846...]]
[[four_minus_pi][4-[pi]][0.85840734641020676153735...]]
]
[endsect][/section Numeric Constants]
[/
Copyright 2008 John Maddock and Paul A. Bristow.
Distributed under the Boost Software License, Version 1.0.
(See accompanying file LICENSE_1_0.txt or copy at
http://www.boost.org/LICENSE_1_0.txt).
]
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