Chris@16: //  (C) Copyright John Maddock 2006.
Chris@16: //  (C) Copyright Johan Rade 2006.
Chris@16: //  (C) Copyright Paul A. Bristow 2011 (added changesign).
Chris@16: 
Chris@16: //  Use, modification and distribution are subject to the
Chris@16: //  Boost Software License, Version 1.0. (See accompanying file
Chris@16: //  LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
Chris@16: 
Chris@16: #ifndef BOOST_MATH_TOOLS_SIGN_HPP
Chris@16: #define BOOST_MATH_TOOLS_SIGN_HPP
Chris@16: 
Chris@16: #ifdef _MSC_VER
Chris@16: #pragma once
Chris@16: #endif
Chris@16: 
Chris@16: #include <boost/math/tools/config.hpp>
Chris@16: #include <boost/math/special_functions/math_fwd.hpp>
Chris@16: #include <boost/math/special_functions/detail/fp_traits.hpp>
Chris@16: 
Chris@16: namespace boost{ namespace math{ 
Chris@16: 
Chris@16: namespace detail {
Chris@16: 
Chris@16:   // signbit
Chris@16: 
Chris@16: #ifdef BOOST_MATH_USE_STD_FPCLASSIFY
Chris@16:     template<class T> 
Chris@16:     inline int signbit_impl(T x, native_tag const&)
Chris@16:     {
Chris@16:         return (std::signbit)(x);
Chris@16:     }
Chris@16: #endif
Chris@16: 
Chris@101:     // Generic versions first, note that these do not handle
Chris@101:     // signed zero or NaN.
Chris@101: 
Chris@101:     template<class T>
Chris@16:     inline int signbit_impl(T x, generic_tag<true> const&)
Chris@16:     {
Chris@16:         return x < 0;
Chris@16:     }
Chris@16: 
Chris@16:     template<class T> 
Chris@16:     inline int signbit_impl(T x, generic_tag<false> const&)
Chris@16:     {
Chris@16:         return x < 0;
Chris@16:     }
Chris@16: 
Chris@101: #if defined(__GNUC__) && (LDBL_MANT_DIG == 106)
Chris@101:     //
Chris@101:     // Special handling for GCC's "double double" type, 
Chris@101:     // in this case the sign is the same as the sign we
Chris@101:     // get by casting to double, no overflow/underflow
Chris@101:     // can occur since the exponents are the same magnitude
Chris@101:     // for the two types:
Chris@101:     //
Chris@101:     inline int signbit_impl(long double x, generic_tag<true> const&)
Chris@101:     {
Chris@101:        return (boost::math::signbit)(static_cast<double>(x));
Chris@101:     }
Chris@101:     inline int signbit_impl(long double x, generic_tag<false> const&)
Chris@101:     {
Chris@101:        return (boost::math::signbit)(static_cast<double>(x));
Chris@101:     }
Chris@101: #endif
Chris@101: 
Chris@101:     template<class T>
Chris@16:     inline int signbit_impl(T x, ieee_copy_all_bits_tag const&)
Chris@16:     {
Chris@16:         typedef BOOST_DEDUCED_TYPENAME fp_traits<T>::type traits;
Chris@16: 
Chris@16:         BOOST_DEDUCED_TYPENAME traits::bits a;
Chris@16:         traits::get_bits(x,a);
Chris@16:         return a & traits::sign ? 1 : 0;
Chris@16:     }
Chris@16: 
Chris@16:     template<class T> 
Chris@16:     inline int signbit_impl(T x, ieee_copy_leading_bits_tag const&)
Chris@16:     {
Chris@16:         typedef BOOST_DEDUCED_TYPENAME fp_traits<T>::type traits;
Chris@16: 
Chris@16:         BOOST_DEDUCED_TYPENAME traits::bits a;
Chris@16:         traits::get_bits(x,a);
Chris@16: 
Chris@16:         return a & traits::sign ? 1 : 0;
Chris@16:     }
Chris@16: 
Chris@16:     // Changesign
Chris@101:     
Chris@101:     // Generic versions first, note that these do not handle
Chris@101:     // signed zero or NaN.
Chris@16: 
Chris@16:     template<class T>
Chris@16:     inline T (changesign_impl)(T x, generic_tag<true> const&)
Chris@16:     {
Chris@16:         return -x;
Chris@16:     }
Chris@16: 
Chris@16:     template<class T>
Chris@16:     inline T (changesign_impl)(T x, generic_tag<false> const&)
Chris@16:     {
Chris@16:         return -x;
Chris@16:     }
Chris@101: #if defined(__GNUC__) && (LDBL_MANT_DIG == 106)
Chris@101:     //
Chris@101:     // Special handling for GCC's "double double" type, 
Chris@101:     // in this case we need to change the sign of both
Chris@101:     // components of the "double double":
Chris@101:     //
Chris@101:     inline long double (changesign_impl)(long double x, generic_tag<true> const&)
Chris@101:     {
Chris@101:        double* pd = reinterpret_cast<double*>(&x);
Chris@101:        pd[0] = boost::math::changesign(pd[0]);
Chris@101:        pd[1] = boost::math::changesign(pd[1]);
Chris@101:        return x;
Chris@101:     }
Chris@101:     inline long double (changesign_impl)(long double x, generic_tag<false> const&)
Chris@101:     {
Chris@101:        double* pd = reinterpret_cast<double*>(&x);
Chris@101:        pd[0] = boost::math::changesign(pd[0]);
Chris@101:        pd[1] = boost::math::changesign(pd[1]);
Chris@101:        return x;
Chris@101:     }
Chris@101: #endif
Chris@16: 
Chris@16:     template<class T>
Chris@16:     inline T changesign_impl(T x, ieee_copy_all_bits_tag const&)
Chris@16:     {
Chris@16:         typedef BOOST_DEDUCED_TYPENAME fp_traits<T>::sign_change_type traits;
Chris@16: 
Chris@16:         BOOST_DEDUCED_TYPENAME traits::bits a;
Chris@16:         traits::get_bits(x,a);
Chris@16:         a ^= traits::sign;
Chris@16:         traits::set_bits(x,a);
Chris@16:         return x;
Chris@16:     }
Chris@16: 
Chris@16:     template<class T>
Chris@16:     inline T (changesign_impl)(T x, ieee_copy_leading_bits_tag const&)
Chris@16:     {
Chris@16:         typedef BOOST_DEDUCED_TYPENAME fp_traits<T>::sign_change_type traits;
Chris@16: 
Chris@16:         BOOST_DEDUCED_TYPENAME traits::bits a;
Chris@16:         traits::get_bits(x,a);
Chris@16:         a ^= traits::sign;
Chris@16:         traits::set_bits(x,a);
Chris@16:         return x;
Chris@16:     }
Chris@16: 
Chris@16: 
Chris@16: }   // namespace detail
Chris@16: 
Chris@16: template<class T> int (signbit)(T x)
Chris@16: { 
Chris@16:    typedef typename detail::fp_traits<T>::type traits;
Chris@16:    typedef typename traits::method method;
Chris@16:    // typedef typename boost::is_floating_point<T>::type fp_tag;
Chris@16:    typedef typename tools::promote_args_permissive<T>::type result_type;
Chris@16:    return detail::signbit_impl(static_cast<result_type>(x), method());
Chris@16: }
Chris@16: 
Chris@16: template <class T>
Chris@16: inline int sign BOOST_NO_MACRO_EXPAND(const T& z)
Chris@16: {
Chris@16:    return (z == 0) ? 0 : (boost::math::signbit)(z) ? -1 : 1;
Chris@16: }
Chris@16: 
Chris@16: template <class T> typename tools::promote_args_permissive<T>::type (changesign)(const T& x)
Chris@16: { //!< \brief return unchanged binary pattern of x, except for change of sign bit. 
Chris@16:    typedef typename detail::fp_traits<T>::sign_change_type traits;
Chris@16:    typedef typename traits::method method;
Chris@16:    // typedef typename boost::is_floating_point<T>::type fp_tag;
Chris@16:    typedef typename tools::promote_args_permissive<T>::type result_type;
Chris@16: 
Chris@16:    return detail::changesign_impl(static_cast<result_type>(x), method());
Chris@16: }
Chris@16: 
Chris@16: template <class T, class U>
Chris@16: inline typename tools::promote_args_permissive<T, U>::type 
Chris@16:    copysign BOOST_NO_MACRO_EXPAND(const T& x, const U& y)
Chris@16: {
Chris@16:    BOOST_MATH_STD_USING
Chris@16:    typedef typename tools::promote_args_permissive<T, U>::type result_type;
Chris@16:    return (boost::math::signbit)(static_cast<result_type>(x)) != (boost::math::signbit)(static_cast<result_type>(y)) 
Chris@16:       ? (boost::math::changesign)(static_cast<result_type>(x)) : static_cast<result_type>(x);
Chris@16: }
Chris@16: 
Chris@16: } // namespace math
Chris@16: } // namespace boost
Chris@16: 
Chris@16: 
Chris@16: #endif // BOOST_MATH_TOOLS_SIGN_HPP
Chris@16: 
Chris@16: