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
20namespace boost{ namespace math{
21
22namespace detail {
23
24 // signbit
25
26#ifdef BOOST_MATH_USE_STD_FPCLASSIFY
27 template<class T>
28 inline int signbit_impl(T x, native_tag const&)
29 {
30 return (std::signbit)(x) ? 1 : 0;
31 }
32#endif
33
34 // Generic versions first, note that these do not handle
35 // signed zero or NaN.
36
37 template<class T>
38 inline int signbit_impl(T x, generic_tag<true> const&)
39 {
40 return x < 0;
41 }
42
43 template<class T>
44 inline int signbit_impl(T x, generic_tag<false> const&)
45 {
46 return x < 0;
47 }
48
49#if defined(__GNUC__) && (LDBL_MANT_DIG == 106)
50 //
51 // Special handling for GCC's "double double" type,
52 // in this case the sign is the same as the sign we
53 // get by casting to double, no overflow/underflow
54 // can occur since the exponents are the same magnitude
55 // for the two types:
56 //
57 inline int signbit_impl(long double x, generic_tag<true> const&)
58 {
59 return (boost::math::signbit)(static_cast<double>(x));
60 }
61 inline int signbit_impl(long double x, generic_tag<false> const&)
62 {
63 return (boost::math::signbit)(static_cast<double>(x));
64 }
65#endif
66
67 template<class T>
68 inline int signbit_impl(T x, ieee_copy_all_bits_tag const&)
69 {
70 typedef BOOST_DEDUCED_TYPENAME fp_traits<T>::type traits;
71
72 BOOST_DEDUCED_TYPENAME traits::bits a;
73 traits::get_bits(x,a);
74 return a & traits::sign ? 1 : 0;
75 }
76
77 template<class T>
78 inline int signbit_impl(T x, ieee_copy_leading_bits_tag const&)
79 {
80 typedef BOOST_DEDUCED_TYPENAME fp_traits<T>::type traits;
81
82 BOOST_DEDUCED_TYPENAME traits::bits a;
83 traits::get_bits(x,a);
84
85 return a & traits::sign ? 1 : 0;
86 }
87
88 // Changesign
89
90 // Generic versions first, note that these do not handle
91 // signed zero or NaN.
92
93 template<class T>
94 inline T (changesign_impl)(T x, generic_tag<true> const&)
95 {
96 return -x;
97 }
98
99 template<class T>
100 inline T (changesign_impl)(T x, generic_tag<false> const&)
101 {
102 return -x;
103 }
104#if defined(__GNUC__) && (LDBL_MANT_DIG == 106)
105 //
106 // Special handling for GCC's "double double" type,
107 // in this case we need to change the sign of both
108 // components of the "double double":
109 //
110 inline long double (changesign_impl)(long double x, generic_tag<true> const&)
111 {
112 double* pd = reinterpret_cast<double*>(&x);
113 pd[0] = boost::math::changesign(pd[0]);
114 pd[1] = boost::math::changesign(pd[1]);
115 return x;
116 }
117 inline long double (changesign_impl)(long double x, generic_tag<false> const&)
118 {
119 double* pd = reinterpret_cast<double*>(&x);
120 pd[0] = boost::math::changesign(pd[0]);
121 pd[1] = boost::math::changesign(pd[1]);
122 return x;
123 }
124#endif
125
126 template<class T>
127 inline T changesign_impl(T x, ieee_copy_all_bits_tag const&)
128 {
129 typedef BOOST_DEDUCED_TYPENAME fp_traits<T>::sign_change_type traits;
130
131 BOOST_DEDUCED_TYPENAME traits::bits a;
132 traits::get_bits(x,a);
133 a ^= traits::sign;
134 traits::set_bits(x,a);
135 return x;
136 }
137
138 template<class T>
139 inline T (changesign_impl)(T x, ieee_copy_leading_bits_tag const&)
140 {
141 typedef BOOST_DEDUCED_TYPENAME fp_traits<T>::sign_change_type traits;
142
143 BOOST_DEDUCED_TYPENAME traits::bits a;
144 traits::get_bits(x,a);
145 a ^= traits::sign;
146 traits::set_bits(x,a);
147 return x;
148 }
149
150
151} // namespace detail
152
153template<class T> int (signbit)(T x)
154{
155 typedef typename detail::fp_traits<T>::type traits;
156 typedef typename traits::method method;
157 // typedef typename boost::is_floating_point<T>::type fp_tag;
158 typedef typename tools::promote_args_permissive<T>::type result_type;
159 return detail::signbit_impl(static_cast<result_type>(x), method());
160}
161
162template <class T>
163inline int sign BOOST_NO_MACRO_EXPAND(const T& z)
164{
165 return (z == 0) ? 0 : (boost::math::signbit)(z) ? -1 : 1;
166}
167
168template <class T> typename tools::promote_args_permissive<T>::type (changesign)(const T& x)
169{ //!< \brief return unchanged binary pattern of x, except for change of sign bit.
170 typedef typename detail::fp_traits<T>::sign_change_type traits;
171 typedef typename traits::method method;
172 // typedef typename boost::is_floating_point<T>::type fp_tag;
173 typedef typename tools::promote_args_permissive<T>::type result_type;
174
175 return detail::changesign_impl(static_cast<result_type>(x), method());
176}
177
178template <class T, class U>
179inline typename tools::promote_args_permissive<T, U>::type
180 copysign BOOST_NO_MACRO_EXPAND(const T& x, const U& y)
181{
182 BOOST_MATH_STD_USING
183 typedef typename tools::promote_args_permissive<T, U>::type result_type;
184 return (boost::math::signbit)(static_cast<result_type>(x)) != (boost::math::signbit)(static_cast<result_type>(y))
185 ? (boost::math::changesign)(static_cast<result_type>(x)) : static_cast<result_type>(x);
186}
187
188} // namespace math
189} // namespace boost
190
191
192#endif // BOOST_MATH_TOOLS_SIGN_HPP
193
194
195

source code of include/boost/math/special_functions/sign.hpp