100 lines
3.4 KiB
C++
100 lines
3.4 KiB
C++
//[preprocessed_pi
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// Preprocessed pi constant, annotated.
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namespace boost
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{
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namespace math
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{
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namespace constants
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{
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namespace detail
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{
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template <class T> struct constant_pi
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{
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private:
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// Default implementations from string of decimal digits:
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static inline T get_from_string()
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{
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static const T result
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= detail::convert_from_string<T>("3.14159265358979323846264338327950288419716939937510582097494459230781640628620899862803482534211706798214808651e+00",
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boost::is_convertible<const char*, T>());
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return result;
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}
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template <int N> static T compute();
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public:
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// Default implementations from string of decimal digits:
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static inline T get(const mpl::int_<construct_from_string>&)
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{
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constant_initializer<T, & constant_pi<T>::get_from_string >::do_nothing();
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return get_from_string();
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}
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// Float, double and long double versions:
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static inline T get(const mpl::int_<construct_from_float>)
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{
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return 3.141592653589793238462643383279502884e+00F;
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}
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static inline T get(const mpl::int_<construct_from_double>&)
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{
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return 3.141592653589793238462643383279502884e+00;
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}
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static inline T get(const mpl::int_<construct_from_long_double>&)
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{
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return 3.141592653589793238462643383279502884e+00L;
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}
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// For very high precision that is nonetheless can be calculated at compile time:
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template <int N> static inline T get(const mpl::int_<N>& n)
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{
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constant_initializer2<T, N, & constant_pi<T>::template compute<N> >::do_nothing();
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return compute<N>();
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}
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//For true arbitrary precision, which may well vary at runtime.
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static inline T get(const mpl::int_<0>&)
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{
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return tools::digits<T>() > max_string_digits ? compute<0>() : get(mpl::int_<construct_from_string>());
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}
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}; // template <class T> struct constant_pi
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} // namespace detail
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// The actual forwarding function (including policy to control precision).
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template <class T, class Policy> inline T pi( )
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{
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return detail:: constant_pi<T>::get(typename construction_traits<T, Policy>::type());
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}
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// The actual forwarding function (using default policy to control precision).
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template <class T> inline T pi()
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{
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return pi<T, boost::math::policies::policy<> >()
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}
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} // namespace constants
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// Namespace specific versions, for the three built-in floats:
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namespace float_constants
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{
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static const float pi = 3.141592653589793238462643383279502884e+00F;
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}
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namespace double_constants
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{
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static const double pi = 3.141592653589793238462643383279502884e+00;
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}
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namespace long_double_constants
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{
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static const long double pi = 3.141592653589793238462643383279502884e+00L;
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}
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namespace constants{;
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} // namespace constants
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} // namespace math
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} // namespace boost
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//] [/preprocessed_pi]
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/*
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Copyright 2012 John Maddock and Paul A. Bristow.
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Distributed under the Boost Software License, Version 1.0.
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(See accompanying file LICENSE_1_0.txt or copy at
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http://www.boost.org/LICENSE_1_0.txt)
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*/
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