1 // The -*- C++ -*- type traits classes for internal use in libstdc++
3 // Copyright (C) 2000-2014 Free Software Foundation, Inc.
5 // This file is part of the GNU ISO C++ Library. This library is free
6 // software; you can redistribute it and/or modify it under the
7 // terms of the GNU General Public License as published by the
8 // Free Software Foundation; either version 3, or (at your option)
11 // This library is distributed in the hope that it will be useful,
12 // but WITHOUT ANY WARRANTY; without even the implied warranty of
13 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 // GNU General Public License for more details.
16 // Under Section 7 of GPL version 3, you are granted additional
17 // permissions described in the GCC Runtime Library Exception, version
18 // 3.1, as published by the Free Software Foundation.
20 // You should have received a copy of the GNU General Public License and
21 // a copy of the GCC Runtime Library Exception along with this program;
22 // see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
23 // <http://www.gnu.org/licenses/>.
25 /** @file bits/cpp_type_traits.h
26 * This is an internal header file, included by other library headers.
27 * Do not attempt to use it directly. @headername{ext/type_traits}
30 // Written by Gabriel Dos Reis <dosreis@cmla.ens-cachan.fr>
32 #ifndef _CPP_TYPE_TRAITS_H
33 #define _CPP_TYPE_TRAITS_H 1
35 #pragma GCC system_header
37 #include <bits/c++config.h>
40 // This file provides some compile-time information about various types.
41 // These representations were designed, on purpose, to be constant-expressions
42 // and not types as found in <bits/type_traits.h>. In particular, they
43 // can be used in control structures and the optimizer hopefully will do
46 // Why integral expressions, and not functions nor types?
47 // Firstly, these compile-time entities are used as template-arguments
48 // so function return values won't work: We need compile-time entities.
49 // We're left with types and constant integral expressions.
50 // Secondly, from the point of view of ease of use, type-based compile-time
51 // information is -not- *that* convenient. On has to write lots of
52 // overloaded functions and to hope that the compiler will select the right
53 // one. As a net effect, the overall structure isn't very clear at first
55 // Thirdly, partial ordering and overload resolution (of function templates)
56 // is highly costly in terms of compiler-resource. It is a Good Thing to
57 // keep these resource consumption as least as possible.
59 // See valarray_array.h for a case use.
61 // -- Gaby (dosreis@cmla.ens-cachan.fr) 2000-03-06.
63 // Update 2005: types are also provided and <bits/type_traits.h> has been
67 // Forward declaration hack, should really include this from somewhere.
68 namespace __gnu_cxx _GLIBCXX_VISIBILITY(default)
70 _GLIBCXX_BEGIN_NAMESPACE_VERSION
72 template<typename _Iterator, typename _Container>
73 class __normal_iterator;
75 _GLIBCXX_END_NAMESPACE_VERSION
78 namespace std _GLIBCXX_VISIBILITY(default)
80 _GLIBCXX_BEGIN_NAMESPACE_VERSION
82 struct __true_type { };
83 struct __false_type { };
87 { typedef __false_type __type; };
90 struct __truth_type<true>
91 { typedef __true_type __type; };
93 // N.B. The conversions to bool are needed due to the issue
94 // explained in c++/19404.
95 template<class _Sp, class _Tp>
98 enum { __value = bool(_Sp::__value) || bool(_Tp::__value) };
99 typedef typename __truth_type<__value>::__type __type;
102 // Compare for equality of types.
103 template<typename, typename>
106 enum { __value = 0 };
107 typedef __false_type __type;
110 template<typename _Tp>
111 struct __are_same<_Tp, _Tp>
113 enum { __value = 1 };
114 typedef __true_type __type;
117 // Holds if the template-argument is a void type.
118 template<typename _Tp>
121 enum { __value = 0 };
122 typedef __false_type __type;
126 struct __is_void<void>
128 enum { __value = 1 };
129 typedef __true_type __type;
135 template<typename _Tp>
138 enum { __value = 0 };
139 typedef __false_type __type;
142 // Thirteen specializations (yes there are eleven standard integer
143 // types; <em>long long</em> and <em>unsigned long long</em> are
144 // supported as extensions)
146 struct __is_integer<bool>
148 enum { __value = 1 };
149 typedef __true_type __type;
153 struct __is_integer<char>
155 enum { __value = 1 };
156 typedef __true_type __type;
160 struct __is_integer<signed char>
162 enum { __value = 1 };
163 typedef __true_type __type;
167 struct __is_integer<unsigned char>
169 enum { __value = 1 };
170 typedef __true_type __type;
173 # ifdef _GLIBCXX_USE_WCHAR_T
175 struct __is_integer<wchar_t>
177 enum { __value = 1 };
178 typedef __true_type __type;
182 #if __cplusplus >= 201103L
184 struct __is_integer<char16_t>
186 enum { __value = 1 };
187 typedef __true_type __type;
191 struct __is_integer<char32_t>
193 enum { __value = 1 };
194 typedef __true_type __type;
199 struct __is_integer<short>
201 enum { __value = 1 };
202 typedef __true_type __type;
206 struct __is_integer<unsigned short>
208 enum { __value = 1 };
209 typedef __true_type __type;
213 struct __is_integer<int>
215 enum { __value = 1 };
216 typedef __true_type __type;
220 struct __is_integer<unsigned int>
222 enum { __value = 1 };
223 typedef __true_type __type;
227 struct __is_integer<long>
229 enum { __value = 1 };
230 typedef __true_type __type;
234 struct __is_integer<unsigned long>
236 enum { __value = 1 };
237 typedef __true_type __type;
241 struct __is_integer<long long>
243 enum { __value = 1 };
244 typedef __true_type __type;
248 struct __is_integer<unsigned long long>
250 enum { __value = 1 };
251 typedef __true_type __type;
255 // Floating point types
257 template<typename _Tp>
260 enum { __value = 0 };
261 typedef __false_type __type;
264 // three specializations (float, double and 'long double')
266 struct __is_floating<float>
268 enum { __value = 1 };
269 typedef __true_type __type;
273 struct __is_floating<double>
275 enum { __value = 1 };
276 typedef __true_type __type;
280 struct __is_floating<long double>
282 enum { __value = 1 };
283 typedef __true_type __type;
289 template<typename _Tp>
292 enum { __value = 0 };
293 typedef __false_type __type;
296 template<typename _Tp>
297 struct __is_pointer<_Tp*>
299 enum { __value = 1 };
300 typedef __true_type __type;
304 // Normal iterator type
306 template<typename _Tp>
307 struct __is_normal_iterator
309 enum { __value = 0 };
310 typedef __false_type __type;
313 template<typename _Iterator, typename _Container>
314 struct __is_normal_iterator< __gnu_cxx::__normal_iterator<_Iterator,
317 enum { __value = 1 };
318 typedef __true_type __type;
322 // An arithmetic type is an integer type or a floating point type
324 template<typename _Tp>
325 struct __is_arithmetic
326 : public __traitor<__is_integer<_Tp>, __is_floating<_Tp> >
330 // A scalar type is an arithmetic type or a pointer type
332 template<typename _Tp>
334 : public __traitor<__is_arithmetic<_Tp>, __is_pointer<_Tp> >
338 // For use in std::copy and std::find overloads for streambuf iterators.
340 template<typename _Tp>
343 enum { __value = 0 };
344 typedef __false_type __type;
348 struct __is_char<char>
350 enum { __value = 1 };
351 typedef __true_type __type;
354 #ifdef _GLIBCXX_USE_WCHAR_T
356 struct __is_char<wchar_t>
358 enum { __value = 1 };
359 typedef __true_type __type;
363 template<typename _Tp>
366 enum { __value = 0 };
367 typedef __false_type __type;
371 struct __is_byte<char>
373 enum { __value = 1 };
374 typedef __true_type __type;
378 struct __is_byte<signed char>
380 enum { __value = 1 };
381 typedef __true_type __type;
385 struct __is_byte<unsigned char>
387 enum { __value = 1 };
388 typedef __true_type __type;
392 // Move iterator type
394 template<typename _Tp>
395 struct __is_move_iterator
397 enum { __value = 0 };
398 typedef __false_type __type;
401 #if __cplusplus >= 201103L
402 template<typename _Iterator>
405 template<typename _Iterator>
406 struct __is_move_iterator< move_iterator<_Iterator> >
408 enum { __value = 1 };
409 typedef __true_type __type;
413 _GLIBCXX_END_NAMESPACE_VERSION
416 #endif //_CPP_TYPE_TRAITS_H