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// (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/math_fwd.hpp>
#include <boost/math/special_functions/log1p.hpp>
#include <boost/math/special_functions/expm1.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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