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> |
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 | |
153 | template<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 | |
162 | template <class T> |
163 | inline int sign BOOST_NO_MACRO_EXPAND(const T& z) |
164 | { |
165 | return (z == 0) ? 0 : (boost::math::signbit)(z) ? -1 : 1; |
166 | } |
167 | |
168 | template <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 | |
178 | template <class T, class U> |
179 | inline 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 | |