| // (C) Copyright John Maddock 2006. |
| // Use, modification and distribution are subject to 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) |
| |
| #ifndef BOOST_MATH_SQRT1PM1 |
| #define BOOST_MATH_SQRT1PM1 |
| |
| #ifdef _MSC_VER |
| #pragma once |
| #endif |
| |
| #include <boost/math/special_functions/log1p.hpp> |
| #include <boost/math/special_functions/expm1.hpp> |
| #include <boost/math/special_functions/math_fwd.hpp> |
| |
| // |
| // This algorithm computes sqrt(1+x)-1 for small x: |
| // |
| |
| namespace boost{ namespace math{ |
| |
| template <class T, class Policy> |
| inline typename tools::promote_args<T>::type sqrt1pm1(const T& val, const Policy& pol) |
| { |
| typedef typename tools::promote_args<T>::type result_type; |
| BOOST_MATH_STD_USING |
| |
| if(fabs(result_type(val)) > 0.75) |
| return sqrt(1 + result_type(val)) - 1; |
| return boost::math::expm1(boost::math::log1p(val, pol) / 2, pol); |
| } |
| |
| template <class T> |
| inline typename tools::promote_args<T>::type sqrt1pm1(const T& val) |
| { |
| return sqrt1pm1(val, policies::policy<>()); |
| } |
| |
| } // namespace math |
| } // namespace boost |
| |
| #endif // BOOST_MATH_SQRT1PM1 |
| |
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