1 // (C) Copyright John Maddock 2006.
2 // (C) Copyright Johan Rade 2006.
3 // (C) Copyright Paul A. Bristow 2011 (added changesign).
4
5 // Use, modification and distribution are subject to the
6 // Boost Software License, Version 1.0. (See accompanying file
7 // LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
8
9 #ifndef BOOST_MATH_TOOLS_SIGN_HPP
10 #define BOOST_MATH_TOOLS_SIGN_HPP
11
12 #ifdef _MSC_VER
13 #pragma once
14 #endif
15
16 #include <boost/math/tools/config.hpp>
17 #include <boost/math/special_functions/math_fwd.hpp>
18 #include <boost/math/special_functions/detail/fp_traits.hpp>
19
20 namespace boost{ namespace math{
21
22 namespace detail {
23
24 // signbit
25
26 #ifdef BOOST_MATH_USE_STD_FPCLASSIFY
27 template<class T>
signbit_impl(T x,native_tag const &)28 inline int signbit_impl(T x, native_tag const&)
29 {
30 return (std::signbit)(x);
31 }
32 #endif
33
34 template<class T>
signbit_impl(T x,generic_tag<true> const &)35 inline int signbit_impl(T x, generic_tag<true> const&)
36 {
37 return x < 0;
38 }
39
40 template<class T>
signbit_impl(T x,generic_tag<false> const &)41 inline int signbit_impl(T x, generic_tag<false> const&)
42 {
43 return x < 0;
44 }
45
46 template<class T>
signbit_impl(T x,ieee_copy_all_bits_tag const &)47 inline int signbit_impl(T x, ieee_copy_all_bits_tag const&)
48 {
49 typedef BOOST_DEDUCED_TYPENAME fp_traits<T>::type traits;
50
51 BOOST_DEDUCED_TYPENAME traits::bits a;
52 traits::get_bits(x,a);
53 return a & traits::sign ? 1 : 0;
54 }
55
56 template<class T>
signbit_impl(T x,ieee_copy_leading_bits_tag const &)57 inline int signbit_impl(T x, ieee_copy_leading_bits_tag const&)
58 {
59 typedef BOOST_DEDUCED_TYPENAME fp_traits<T>::type traits;
60
61 BOOST_DEDUCED_TYPENAME traits::bits a;
62 traits::get_bits(x,a);
63
64 return a & traits::sign ? 1 : 0;
65 }
66
67 // Changesign
68
69 template<class T>
T(changesign_impl)70 inline T (changesign_impl)(T x, generic_tag<true> const&)
71 {
72 return -x;
73 }
74
75 template<class T>
T(changesign_impl)76 inline T (changesign_impl)(T x, generic_tag<false> const&)
77 {
78 return -x;
79 }
80
81
82 template<class T>
changesign_impl(T x,ieee_copy_all_bits_tag const &)83 inline T changesign_impl(T x, ieee_copy_all_bits_tag const&)
84 {
85 typedef BOOST_DEDUCED_TYPENAME fp_traits<T>::sign_change_type traits;
86
87 BOOST_DEDUCED_TYPENAME traits::bits a;
88 traits::get_bits(x,a);
89 a ^= traits::sign;
90 traits::set_bits(x,a);
91 return x;
92 }
93
94 template<class T>
T(changesign_impl)95 inline T (changesign_impl)(T x, ieee_copy_leading_bits_tag const&)
96 {
97 typedef BOOST_DEDUCED_TYPENAME fp_traits<T>::sign_change_type traits;
98
99 BOOST_DEDUCED_TYPENAME traits::bits a;
100 traits::get_bits(x,a);
101 a ^= traits::sign;
102 traits::set_bits(x,a);
103 return x;
104 }
105
106
107 } // namespace detail
108
109 template<class T> int (signbit)(T x)
110 {
111 typedef typename detail::fp_traits<T>::type traits;
112 typedef typename traits::method method;
113 typedef typename boost::is_floating_point<T>::type fp_tag;
114 return detail::signbit_impl(x, method());
115 }
116
117 template <class T>
BOOST_NO_MACRO_EXPAND(const T & z)118 inline int sign BOOST_NO_MACRO_EXPAND(const T& z)
119 {
120 return (z == 0) ? 0 : (boost::math::signbit)(z) ? -1 : 1;
121 }
122
T(changesign)123 template<class T> T (changesign)(const T& x)
124 { //!< \brief return unchanged binary pattern of x, except for change of sign bit.
125 typedef typename detail::fp_traits<T>::sign_change_type traits;
126 typedef typename traits::method method;
127 typedef typename boost::is_floating_point<T>::type fp_tag;
128
129 return detail::changesign_impl(x, method());
130 }
131
132 template <class T>
BOOST_NO_MACRO_EXPAND(const T & x,const T & y)133 inline T copysign BOOST_NO_MACRO_EXPAND(const T& x, const T& y)
134 {
135 BOOST_MATH_STD_USING
136 return (boost::math::signbit)(x) != (boost::math::signbit)(y) ? (boost::math::changesign)(x) : x;
137 }
138
139 } // namespace math
140 } // namespace boost
141
142
143 #endif // BOOST_MATH_TOOLS_SIGN_HPP
144
145
146