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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


#ifdef _MSC_VER
#pragma once

#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;

   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