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) ? 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>
signbit_impl(T x,generic_tag<true> const &)38 inline int signbit_impl(T x, generic_tag<true> const&)
39 {
40 return x < 0;
41 }
42
43 template<class T>
signbit_impl(T x,generic_tag<false> const &)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 //
signbit_impl(long double x,generic_tag<true> const &)57 inline int signbit_impl(long double x, generic_tag<true> const&)
58 {
59 return (boost::math::signbit)(static_cast<double>(x));
60 }
signbit_impl(long double x,generic_tag<false> const &)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>
signbit_impl(T x,ieee_copy_all_bits_tag const &)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>
signbit_impl(T x,ieee_copy_leading_bits_tag const &)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>
T(changesign_impl)94 inline T (changesign_impl)(T x, generic_tag<true> const&)
95 {
96 return -x;
97 }
98
99 template<class T>
T(changesign_impl)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>
changesign_impl(T x,ieee_copy_all_bits_tag const &)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>
T(changesign_impl)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>
BOOST_NO_MACRO_EXPAND(const T & z)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
type(changesign)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
BOOST_NO_MACRO_EXPAND(const T & x,const U & y)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