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48 lines
1.1 KiB
48 lines
1.1 KiB
// (C) Copyright John Maddock 2006. |
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// Use, modification and distribution are subject to the |
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// Boost Software License, Version 1.0. (See accompanying file |
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// LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) |
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#ifndef BOOST_MATH_SQRT1PM1 |
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#define BOOST_MATH_SQRT1PM1 |
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#ifdef _MSC_VER |
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#pragma once |
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#endif |
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#include <boost/math/special_functions/log1p.hpp> |
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#include <boost/math/special_functions/expm1.hpp> |
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#include <boost/math/special_functions/math_fwd.hpp> |
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// |
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// This algorithm computes sqrt(1+x)-1 for small x: |
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// |
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namespace boost{ namespace math{ |
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template <class T, class Policy> |
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inline typename tools::promote_args<T>::type sqrt1pm1(const T& val, const Policy& pol) |
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{ |
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typedef typename tools::promote_args<T>::type result_type; |
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BOOST_MATH_STD_USING |
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if(fabs(result_type(val)) > 0.75) |
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return sqrt(1 + result_type(val)) - 1; |
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return boost::math::expm1(boost::math::log1p(val, pol) / 2, pol); |
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} |
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template <class T> |
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inline typename tools::promote_args<T>::type sqrt1pm1(const T& val) |
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{ |
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return sqrt1pm1(val, policies::policy<>()); |
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} |
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} // namespace math |
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} // namespace boost |
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#endif // BOOST_MATH_SQRT1PM1 |
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