// boost asinh.hpp header file | |
// (C) Copyright Eric Ford & Hubert Holin 2001. | |
// (C) Copyright John Maddock 2008. | |
// 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) | |
// See http://www.boost.org for updates, documentation, and revision history. | |
#ifndef BOOST_ASINH_HPP | |
#define BOOST_ASINH_HPP | |
#ifdef _MSC_VER | |
#pragma once | |
#endif | |
#include <boost/config/no_tr1/cmath.hpp> | |
#include <boost/config.hpp> | |
#include <boost/math/tools/precision.hpp> | |
#include <boost/math/special_functions/math_fwd.hpp> | |
#include <boost/math/special_functions/sqrt1pm1.hpp> | |
#include <boost/math/special_functions/log1p.hpp> | |
// This is the inverse of the hyperbolic sine function. | |
namespace boost | |
{ | |
namespace math | |
{ | |
namespace detail{ | |
#if defined(__GNUC__) && (__GNUC__ < 3) | |
// gcc 2.x ignores function scope using declarations, | |
// put them in the scope of the enclosing namespace instead: | |
using ::std::abs; | |
using ::std::sqrt; | |
using ::std::log; | |
using ::std::numeric_limits; | |
#endif | |
template<typename T, class Policy> | |
inline T asinh_imp(const T x, const Policy& pol) | |
{ | |
BOOST_MATH_STD_USING | |
if (x >= tools::forth_root_epsilon<T>()) | |
{ | |
if (x > 1 / tools::root_epsilon<T>()) | |
{ | |
// http://functions.wolfram.com/ElementaryFunctions/ArcSinh/06/01/06/01/0001/ | |
// approximation by laurent series in 1/x at 0+ order from -1 to 1 | |
return log(x * 2) + 1/ (4 * x * x); | |
} | |
else if(x < 0.5f) | |
{ | |
// As below, but rearranged to preserve digits: | |
return boost::math::log1p(x + boost::math::sqrt1pm1(x * x, pol), pol); | |
} | |
else | |
{ | |
// http://functions.wolfram.com/ElementaryFunctions/ArcSinh/02/ | |
return( log( x + sqrt(x*x+1) ) ); | |
} | |
} | |
else if (x <= -tools::forth_root_epsilon<T>()) | |
{ | |
return(-asinh(-x)); | |
} | |
else | |
{ | |
// http://functions.wolfram.com/ElementaryFunctions/ArcSinh/06/01/03/01/0001/ | |
// approximation by taylor series in x at 0 up to order 2 | |
T result = x; | |
if (abs(x) >= tools::root_epsilon<T>()) | |
{ | |
T x3 = x*x*x; | |
// approximation by taylor series in x at 0 up to order 4 | |
result -= x3/static_cast<T>(6); | |
} | |
return(result); | |
} | |
} | |
} | |
template<typename T> | |
inline typename tools::promote_args<T>::type asinh(T x) | |
{ | |
return boost::math::asinh(x, policies::policy<>()); | |
} | |
template<typename T, typename Policy> | |
inline typename tools::promote_args<T>::type asinh(T x, const Policy&) | |
{ | |
typedef typename tools::promote_args<T>::type result_type; | |
typedef typename policies::evaluation<result_type, Policy>::type value_type; | |
typedef typename policies::normalise< | |
Policy, | |
policies::promote_float<false>, | |
policies::promote_double<false>, | |
policies::discrete_quantile<>, | |
policies::assert_undefined<> >::type forwarding_policy; | |
return policies::checked_narrowing_cast<result_type, forwarding_policy>( | |
detail::asinh_imp(static_cast<value_type>(x), forwarding_policy()), | |
"boost::math::asinh<%1%>(%1%)"); | |
} | |
} | |
} | |
#endif /* BOOST_ASINH_HPP */ | |