libstdc++
ext/numeric_traits.h
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1// -*- C++ -*-
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4//
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18// 3.1, as published by the Free Software Foundation.
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24
25/** @file ext/numeric_traits.h
26 * This file is a GNU extension to the Standard C++ Library.
27 */
28
29#ifndef _EXT_NUMERIC_TRAITS
30#define _EXT_NUMERIC_TRAITS 1
31
32#pragma GCC system_header
33
34#include <bits/cpp_type_traits.h>
35#include <ext/type_traits.h>
36
37namespace __gnu_cxx _GLIBCXX_VISIBILITY(default)
38{
39_GLIBCXX_BEGIN_NAMESPACE_VERSION
40
41 // Compile time constants for builtin types.
42 // In C++98 std::numeric_limits member functions are not constant expressions
43 // (that changed in C++11 with the addition of 'constexpr').
44 // Even for C++11, this header is smaller than <limits> and can be used
45 // when only is_signed, digits, min, or max values are needed for integers,
46 // or is_signed, digits10, max_digits10, or max_exponent10 for floats.
47
48 // Unlike __is_integer (and std::is_integral) this trait is true for
49 // non-standard built-in integer types such as __int128 and __int20.
50 template<typename _Tp>
51 struct __is_integer_nonstrict
52 : public std::__is_integer<_Tp>
53 {
54 using std::__is_integer<_Tp>::__value;
55
56 // The number of bits in the value representation.
57 enum { __width = __value ? sizeof(_Tp) * __CHAR_BIT__ : 0 };
58 };
59
60 template<typename _Value>
61 struct __numeric_traits_integer
62 {
63#if __cplusplus >= 201103L
64 static_assert(__is_integer_nonstrict<_Value>::__value,
65 "invalid specialization");
66#endif
67
68 // NB: these two are also available in std::numeric_limits as compile
69 // time constants, but <limits> is big and we can avoid including it.
70 static const bool __is_signed = (_Value)(-1) < 0;
71 static const int __digits
72 = __is_integer_nonstrict<_Value>::__width - __is_signed;
73
74 // The initializers must be constants so that __max and __min are too.
75 static const _Value __max = __is_signed
76 ? (((((_Value)1 << (__digits - 1)) - 1) << 1) + 1)
77 : ~(_Value)0;
78 static const _Value __min = __is_signed ? -__max - 1 : (_Value)0;
79 };
80
81 template<typename _Value>
82 const _Value __numeric_traits_integer<_Value>::__min;
83
84 template<typename _Value>
85 const _Value __numeric_traits_integer<_Value>::__max;
86
87 template<typename _Value>
88 const bool __numeric_traits_integer<_Value>::__is_signed;
89
90 template<typename _Value>
91 const int __numeric_traits_integer<_Value>::__digits;
92
93 // Enable __numeric_traits_integer for types where the __is_integer_nonstrict
94 // primary template doesn't give the right answer.
95#define _GLIBCXX_INT_N_TRAITS(T, WIDTH) \
96 __extension__ \
97 template<> struct __is_integer_nonstrict<T> \
98 { \
99 enum { __value = 1 }; \
100 typedef std::__true_type __type; \
101 enum { __width = WIDTH }; \
102 }; \
103 __extension__ \
104 template<> struct __is_integer_nonstrict<unsigned T> \
105 { \
106 enum { __value = 1 }; \
107 typedef std::__true_type __type; \
108 enum { __width = WIDTH }; \
109 };
110
111 // We need to specify the width for some __intNN types because they
112 // have padding bits, e.g. the object representation of __int20 has 32 bits,
113 // but its width (number of bits in the value representation) is only 20.
114#if defined __GLIBCXX_TYPE_INT_N_0 && __GLIBCXX_BITSIZE_INT_N_0 % __CHAR_BIT__
115 _GLIBCXX_INT_N_TRAITS(__GLIBCXX_TYPE_INT_N_0, __GLIBCXX_BITSIZE_INT_N_0)
116#endif
117#if defined __GLIBCXX_TYPE_INT_N_1 && __GLIBCXX_BITSIZE_INT_N_1 % __CHAR_BIT__
118 _GLIBCXX_INT_N_TRAITS(__GLIBCXX_TYPE_INT_N_1, __GLIBCXX_BITSIZE_INT_N_1)
119#endif
120#if defined __GLIBCXX_TYPE_INT_N_2 && __GLIBCXX_BITSIZE_INT_N_2 % __CHAR_BIT__
121 _GLIBCXX_INT_N_TRAITS(__GLIBCXX_TYPE_INT_N_2, __GLIBCXX_BITSIZE_INT_N_2)
122#endif
123#if defined __GLIBCXX_TYPE_INT_N_3 && __GLIBCXX_BITSIZE_INT_N_3 % __CHAR_BIT__
124 _GLIBCXX_INT_N_TRAITS(__GLIBCXX_TYPE_INT_N_3, __GLIBCXX_BITSIZE_INT_N_3)
125#endif
126
127#if defined __STRICT_ANSI__ && defined __SIZEOF_INT128__
128 // In strict modes __is_integer<__int128> is false,
129 // but we still want to define __numeric_traits_integer<__int128>.
130 _GLIBCXX_INT_N_TRAITS(__int128, 128)
131#endif
132
133#undef _GLIBCXX_INT_N_TRAITS
134
135#if __cplusplus >= 201103L
136 /// Convenience alias for __numeric_traits<integer-type>.
137 template<typename _Tp>
138 using __int_traits = __numeric_traits_integer<_Tp>;
139#endif
140
141#define __glibcxx_floating(_Tp, _Fval, _Dval, _LDval) \
142 (std::__are_same<_Tp, float>::__value ? _Fval \
143 : std::__are_same<_Tp, double>::__value ? _Dval : _LDval)
144
145#define __glibcxx_max_digits10(_Tp) \
146 (2 + __glibcxx_floating(_Tp, __FLT_MANT_DIG__, __DBL_MANT_DIG__, \
147 __LDBL_MANT_DIG__) * 643L / 2136)
148
149#define __glibcxx_digits10(_Tp) \
150 __glibcxx_floating(_Tp, __FLT_DIG__, __DBL_DIG__, __LDBL_DIG__)
151
152#define __glibcxx_max_exponent10(_Tp) \
153 __glibcxx_floating(_Tp, __FLT_MAX_10_EXP__, __DBL_MAX_10_EXP__, \
154 __LDBL_MAX_10_EXP__)
155
156 // N.B. this only supports float, double and long double (no __float128 etc.)
157 template<typename _Value>
158 struct __numeric_traits_floating
159 {
160 // Only floating point types. See N1822.
161 static const int __max_digits10 = __glibcxx_max_digits10(_Value);
162
163 // See above comment...
164 static const bool __is_signed = true;
165 static const int __digits10 = __glibcxx_digits10(_Value);
166 static const int __max_exponent10 = __glibcxx_max_exponent10(_Value);
167 };
168
169 template<typename _Value>
170 const int __numeric_traits_floating<_Value>::__max_digits10;
171
172 template<typename _Value>
173 const bool __numeric_traits_floating<_Value>::__is_signed;
174
175 template<typename _Value>
176 const int __numeric_traits_floating<_Value>::__digits10;
177
178 template<typename _Value>
179 const int __numeric_traits_floating<_Value>::__max_exponent10;
180
181#undef __glibcxx_floating
182#undef __glibcxx_max_digits10
183#undef __glibcxx_digits10
184#undef __glibcxx_max_exponent10
185
186 template<typename _Value>
187 struct __numeric_traits
188 : public __numeric_traits_integer<_Value>
189 { };
190
191 template<>
192 struct __numeric_traits<float>
193 : public __numeric_traits_floating<float>
194 { };
195
196 template<>
197 struct __numeric_traits<double>
198 : public __numeric_traits_floating<double>
199 { };
200
201 template<>
202 struct __numeric_traits<long double>
203 : public __numeric_traits_floating<long double>
204 { };
205
206#ifdef _GLIBCXX_LONG_DOUBLE_ALT128_COMPAT
207# if defined __LONG_DOUBLE_IEEE128__
208 // long double is __ieee128, define traits for __ibm128
209 template<>
210 struct __numeric_traits_floating<__ibm128>
211 {
212 static const int __max_digits10 = 33;
213 static const bool __is_signed = true;
214 static const int __digits10 = 31;
215 static const int __max_exponent10 = 308;
216 };
217 template<>
218 struct __numeric_traits<__ibm128>
219 : public __numeric_traits_floating<__ibm128>
220 { };
221# elif defined __LONG_DOUBLE_IBM128__
222 // long double is __ibm128, define traits for __ieee128
223 template<>
224 struct __numeric_traits_floating<__ieee128>
225 {
226 static const int __max_digits10 = 36;
227 static const bool __is_signed = true;
228 static const int __digits10 = 33;
229 static const int __max_exponent10 = 4932;
230 };
231 template<>
232 struct __numeric_traits<__ieee128>
233 : public __numeric_traits_floating<__ieee128>
234 { };
235# endif
236#endif
237
238_GLIBCXX_END_NAMESPACE_VERSION
239} // namespace
240
241#endif
__gnu_cxx
GNU extensions for public use.
__gnu_cxx::__int_traits
__numeric_traits_integer< _Tp > __int_traits
Convenience alias for __numeric_traits<integer-type>.
Definition: ext/numeric_traits.h:138