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// (C) Copyright John Maddock 2006.
// (C) Copyright Johan Rade 2006.
// (C) Copyright Paul A. Bristow 2011 (added changesign).
// 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_TOOLS_SIGN_HPP
#define BOOST_MATH_TOOLS_SIGN_HPP
#ifdef _MSC_VER
#pragma once
#endif
#include <boost/math/tools/config.hpp>
#include <boost/math/special_functions/math_fwd.hpp>
#include <boost/math/special_functions/detail/fp_traits.hpp>
namespace boost{ namespace math{
namespace detail {
// signbit
#ifdef BOOST_MATH_USE_STD_FPCLASSIFY
template<class T>
inline int signbit_impl(T x, native_tag const&)
{
return (std::signbit)(x);
}
#endif
// Generic versions first, note that these do not handle
// signed zero or NaN.
template<class T>
inline int signbit_impl(T x, generic_tag<true> const&)
{
return x < 0;
}
template<class T>
inline int signbit_impl(T x, generic_tag<false> const&)
{
return x < 0;
}
#if defined(__GNUC__) && (LDBL_MANT_DIG == 106)
//
// Special handling for GCC's "double double" type,
// in this case the sign is the same as the sign we
// get by casting to double, no overflow/underflow
// can occur since the exponents are the same magnitude
// for the two types:
//
inline int signbit_impl(long double x, generic_tag<true> const&)
{
return (boost::math::signbit)(static_cast<double>(x));
}
inline int signbit_impl(long double x, generic_tag<false> const&)
{
return (boost::math::signbit)(static_cast<double>(x));
}
#endif
template<class T>
inline int signbit_impl(T x, ieee_copy_all_bits_tag const&)
{
typedef BOOST_DEDUCED_TYPENAME fp_traits<T>::type traits;
BOOST_DEDUCED_TYPENAME traits::bits a;
traits::get_bits(x,a);
return a & traits::sign ? 1 : 0;
}
template<class T>
inline int signbit_impl(T x, ieee_copy_leading_bits_tag const&)
{
typedef BOOST_DEDUCED_TYPENAME fp_traits<T>::type traits;
BOOST_DEDUCED_TYPENAME traits::bits a;
traits::get_bits(x,a);
return a & traits::sign ? 1 : 0;
}
// Changesign
// Generic versions first, note that these do not handle
// signed zero or NaN.
template<class T>
inline T (changesign_impl)(T x, generic_tag<true> const&)
{
return -x;
}
template<class T>
inline T (changesign_impl)(T x, generic_tag<false> const&)
{
return -x;
}
#if defined(__GNUC__) && (LDBL_MANT_DIG == 106)
//
// Special handling for GCC's "double double" type,
// in this case we need to change the sign of both
// components of the "double double":
//
inline long double (changesign_impl)(long double x, generic_tag<true> const&)
{
double* pd = reinterpret_cast<double*>(&x);
pd[0] = boost::math::changesign(pd[0]);
pd[1] = boost::math::changesign(pd[1]);
return x;
}
inline long double (changesign_impl)(long double x, generic_tag<false> const&)
{
double* pd = reinterpret_cast<double*>(&x);
pd[0] = boost::math::changesign(pd[0]);
pd[1] = boost::math::changesign(pd[1]);
return x;
}
#endif
template<class T>
inline T changesign_impl(T x, ieee_copy_all_bits_tag const&)
{
typedef BOOST_DEDUCED_TYPENAME fp_traits<T>::sign_change_type traits;
BOOST_DEDUCED_TYPENAME traits::bits a;
traits::get_bits(x,a);
a ^= traits::sign;
traits::set_bits(x,a);
return x;
}
template<class T>
inline T (changesign_impl)(T x, ieee_copy_leading_bits_tag const&)
{
typedef BOOST_DEDUCED_TYPENAME fp_traits<T>::sign_change_type traits;
BOOST_DEDUCED_TYPENAME traits::bits a;
traits::get_bits(x,a);
a ^= traits::sign;
traits::set_bits(x,a);
return x;
}
} // namespace detail
template<class T> int (signbit)(T x)
{
typedef typename detail::fp_traits<T>::type traits;
typedef typename traits::method method;
// typedef typename boost::is_floating_point<T>::type fp_tag;
typedef typename tools::promote_args_permissive<T>::type result_type;
return detail::signbit_impl(static_cast<result_type>(x), method());
}
template <class T>
inline int sign BOOST_NO_MACRO_EXPAND(const T& z)
{
return (z == 0) ? 0 : (boost::math::signbit)(z) ? -1 : 1;
}
template <class T> typename tools::promote_args_permissive<T>::type (changesign)(const T& x)
{ //!< \brief return unchanged binary pattern of x, except for change of sign bit.
typedef typename detail::fp_traits<T>::sign_change_type traits;
typedef typename traits::method method;
// typedef typename boost::is_floating_point<T>::type fp_tag;
typedef typename tools::promote_args_permissive<T>::type result_type;
return detail::changesign_impl(static_cast<result_type>(x), method());
}
template <class T, class U>
inline typename tools::promote_args_permissive<T, U>::type
copysign BOOST_NO_MACRO_EXPAND(const T& x, const U& y)
{
BOOST_MATH_STD_USING
typedef typename tools::promote_args_permissive<T, U>::type result_type;
return (boost::math::signbit)(static_cast<result_type>(x)) != (boost::math::signbit)(static_cast<result_type>(y))
? (boost::math::changesign)(static_cast<result_type>(x)) : static_cast<result_type>(x);
}
} // namespace math
} // namespace boost
#endif // BOOST_MATH_TOOLS_SIGN_HPP
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