1 // C++0x type_traits -*- C++ -*-
3 // Copyright (C) 2007, 2008, 2009 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 include/type_traits
26 * This is a Standard C++ Library header.
29 #ifndef _GLIBCXX_TYPE_TRAITS
30 #define _GLIBCXX_TYPE_TRAITS 1
32 #pragma GCC system_header
34 #ifndef __GXX_EXPERIMENTAL_CXX0X__
35 # include <c++0x_warning.h>
38 #if defined(_GLIBCXX_INCLUDE_AS_TR1)
39 # error C++0x header cannot be included from TR1 header
44 #if defined(_GLIBCXX_INCLUDE_AS_CXX0X)
45 # include <tr1_impl/type_traits>
47 # define _GLIBCXX_INCLUDE_AS_CXX0X
48 # define _GLIBCXX_BEGIN_NAMESPACE_TR1
49 # define _GLIBCXX_END_NAMESPACE_TR1
51 # include <tr1_impl/type_traits>
53 # undef _GLIBCXX_END_NAMESPACE_TR1
54 # undef _GLIBCXX_BEGIN_NAMESPACE_TR1
55 # undef _GLIBCXX_INCLUDE_AS_CXX0X
61 * @addtogroup metaprogramming
65 // Primary classification traits.
67 /// is_lvalue_reference
69 struct is_lvalue_reference
70 : public false_type { };
72 template<typename _Tp>
73 struct is_lvalue_reference<_Tp&>
74 : public true_type { };
76 /// is_rvalue_reference
78 struct is_rvalue_reference
79 : public false_type { };
81 template<typename _Tp>
82 struct is_rvalue_reference<_Tp&&>
83 : public true_type { };
85 // Secondary classification traits.
88 template<typename _Tp>
90 : public integral_constant<bool, (is_lvalue_reference<_Tp>::value
91 || is_rvalue_reference<_Tp>::value)>
94 // Reference transformations.
97 template<typename _Tp>
98 struct remove_reference
99 { typedef _Tp type; };
101 template<typename _Tp>
102 struct remove_reference<_Tp&>
103 { typedef _Tp type; };
105 template<typename _Tp>
106 struct remove_reference<_Tp&&>
107 { typedef _Tp type; };
109 template<typename _Tp,
110 bool = !is_reference<_Tp>::value && !is_void<_Tp>::value,
111 bool = is_rvalue_reference<_Tp>::value>
112 struct __add_lvalue_reference_helper
113 { typedef _Tp type; };
115 template<typename _Tp>
116 struct __add_lvalue_reference_helper<_Tp, true, false>
117 { typedef _Tp& type; };
119 template<typename _Tp>
120 struct __add_lvalue_reference_helper<_Tp, false, true>
121 { typedef typename remove_reference<_Tp>::type& type; };
123 /// add_lvalue_reference
124 template<typename _Tp>
125 struct add_lvalue_reference
126 : public __add_lvalue_reference_helper<_Tp>
129 template<typename _Tp,
130 bool = !is_reference<_Tp>::value && !is_void<_Tp>::value>
131 struct __add_rvalue_reference_helper
132 { typedef _Tp type; };
134 template<typename _Tp>
135 struct __add_rvalue_reference_helper<_Tp, true>
136 { typedef _Tp&& type; };
138 /// add_rvalue_reference
139 template<typename _Tp>
140 struct add_rvalue_reference
141 : public __add_rvalue_reference_helper<_Tp>
144 // Scalar properties and transformations.
146 template<typename _Tp,
147 bool = is_integral<_Tp>::value,
148 bool = is_floating_point<_Tp>::value>
149 struct __is_signed_helper
150 : public false_type { };
152 template<typename _Tp>
153 struct __is_signed_helper<_Tp, false, true>
154 : public true_type { };
156 template<typename _Tp>
157 struct __is_signed_helper<_Tp, true, false>
158 : public integral_constant<bool, static_cast<bool>(_Tp(-1) < _Tp(0))>
162 template<typename _Tp>
164 : public integral_constant<bool, __is_signed_helper<_Tp>::value>
168 template<typename _Tp>
170 : public integral_constant<bool, (is_arithmetic<_Tp>::value
171 && !is_signed<_Tp>::value)>
174 // Member introspection.
177 // Could use is_standard_layout && is_trivial instead of the builtin.
178 template<typename _Tp>
180 : public integral_constant<bool, __is_pod(_Tp)>
183 /// is_standard_layout
184 template<typename _Tp>
185 struct is_standard_layout
186 : public integral_constant<bool, __is_standard_layout(_Tp)>
189 /// has_trivial_default_constructor
190 template<typename _Tp>
191 struct has_trivial_default_constructor
192 : public integral_constant<bool, __has_trivial_constructor(_Tp)>
195 /// has_trivial_copy_constructor
196 template<typename _Tp>
197 struct has_trivial_copy_constructor
198 : public integral_constant<bool, __has_trivial_copy(_Tp)>
201 /// has_trivial_assign
202 template<typename _Tp>
203 struct has_trivial_assign
204 : public integral_constant<bool, __has_trivial_assign(_Tp)>
207 /// has_trivial_destructor
208 template<typename _Tp>
209 struct has_trivial_destructor
210 : public integral_constant<bool, __has_trivial_destructor(_Tp)>
214 template<typename _Tp>
216 : public integral_constant<bool, __is_trivial(_Tp)>
219 /// has_nothrow_default_constructor
220 template<typename _Tp>
221 struct has_nothrow_default_constructor
222 : public integral_constant<bool, __has_nothrow_constructor(_Tp)>
225 /// has_nothrow_copy_constructor
226 template<typename _Tp>
227 struct has_nothrow_copy_constructor
228 : public integral_constant<bool, __has_nothrow_copy(_Tp)>
231 /// has_nothrow_assign
232 template<typename _Tp>
233 struct has_nothrow_assign
234 : public integral_constant<bool, __has_nothrow_assign(_Tp)>
238 template<typename _Base, typename _Derived>
240 : public integral_constant<bool, __is_base_of(_Base, _Derived)>
243 template<typename _Tp>
244 typename add_rvalue_reference<_Tp>::type declval();
246 // Relationships between types.
247 template<typename _From, typename _To,
248 bool = (is_void<_From>::value || is_void<_To>::value
249 || is_function<_To>::value || is_array<_To>::value)>
250 struct __is_convertible_helper
251 { static const bool __value = (is_void<_From>::value
252 && is_void<_To>::value); };
254 template<typename _From, typename _To>
255 struct __is_convertible_helper<_From, _To, false>
256 : public __sfinae_types
259 static __one __test(_To);
260 static __two __test(...);
263 static const bool __value = sizeof(__test(declval<_From>())) == 1;
267 // The C++0x specifications require front-end support, see N2255.
269 template<typename _From, typename _To>
270 struct is_convertible
271 : public integral_constant<bool,
272 __is_convertible_helper<_From, _To>::__value>
275 template<std::size_t _Len>
276 struct __aligned_storage_msa
280 unsigned char __data[_Len];
281 struct __attribute__((__aligned__)) { } __align;
286 * @brief Alignment type.
288 * The value of _Align is a default-alignment which shall be the
289 * most stringent alignment requirement for any C++ object type
290 * whose size is no greater than _Len (3.9). The member typedef
291 * type shall be a POD type suitable for use as uninitialized
292 * storage for any object whose size is at most _Len and whose
293 * alignment is a divisor of _Align.
295 template<std::size_t _Len, std::size_t _Align =
296 __alignof__(typename __aligned_storage_msa<_Len>::__type)>
297 struct aligned_storage
301 unsigned char __data[_Len];
302 struct __attribute__((__aligned__((_Align)))) { } __align;
307 // Define a nested type if some predicate holds.
310 template<bool, typename _Tp = void>
314 // Partial specialization for true.
315 template<typename _Tp>
316 struct enable_if<true, _Tp>
317 { typedef _Tp type; };
320 // A conditional expression, but for types. If true, first, if false, second.
323 template<bool _Cond, typename _Iftrue, typename _Iffalse>
325 { typedef _Iftrue type; };
327 // Partial specialization for false.
328 template<typename _Iftrue, typename _Iffalse>
329 struct conditional<false, _Iftrue, _Iffalse>
330 { typedef _Iffalse type; };
333 // Decay trait for arrays and functions, used for perfect forwarding
334 // in make_pair, make_tuple, etc.
335 template<typename _Up,
336 bool _IsArray = is_array<_Up>::value,
337 bool _IsFunction = is_function<_Up>::value>
338 struct __decay_selector;
341 template<typename _Up>
342 struct __decay_selector<_Up, false, false>
343 { typedef typename remove_cv<_Up>::type __type; };
345 template<typename _Up>
346 struct __decay_selector<_Up, true, false>
347 { typedef typename remove_extent<_Up>::type* __type; };
349 template<typename _Up>
350 struct __decay_selector<_Up, false, true>
351 { typedef typename add_pointer<_Up>::type __type; };
354 template<typename _Tp>
358 typedef typename remove_reference<_Tp>::type __remove_type;
361 typedef typename __decay_selector<__remove_type>::__type type;
365 // Utility for constructing identically cv-qualified types.
366 template<typename _Unqualified, bool _IsConst, bool _IsVol>
367 struct __cv_selector;
369 template<typename _Unqualified>
370 struct __cv_selector<_Unqualified, false, false>
371 { typedef _Unqualified __type; };
373 template<typename _Unqualified>
374 struct __cv_selector<_Unqualified, false, true>
375 { typedef volatile _Unqualified __type; };
377 template<typename _Unqualified>
378 struct __cv_selector<_Unqualified, true, false>
379 { typedef const _Unqualified __type; };
381 template<typename _Unqualified>
382 struct __cv_selector<_Unqualified, true, true>
383 { typedef const volatile _Unqualified __type; };
385 template<typename _Qualified, typename _Unqualified,
386 bool _IsConst = is_const<_Qualified>::value,
387 bool _IsVol = is_volatile<_Qualified>::value>
388 struct __match_cv_qualifiers
391 typedef __cv_selector<_Unqualified, _IsConst, _IsVol> __match;
394 typedef typename __match::__type __type;
398 // Utility for finding the unsigned versions of signed integral types.
399 template<typename _Tp>
400 struct __make_unsigned
401 { typedef _Tp __type; };
404 struct __make_unsigned<char>
405 { typedef unsigned char __type; };
408 struct __make_unsigned<signed char>
409 { typedef unsigned char __type; };
412 struct __make_unsigned<short>
413 { typedef unsigned short __type; };
416 struct __make_unsigned<int>
417 { typedef unsigned int __type; };
420 struct __make_unsigned<long>
421 { typedef unsigned long __type; };
424 struct __make_unsigned<long long>
425 { typedef unsigned long long __type; };
428 // Select between integral and enum: not possible to be both.
429 template<typename _Tp,
430 bool _IsInt = is_integral<_Tp>::value,
431 bool _IsEnum = is_enum<_Tp>::value>
432 struct __make_unsigned_selector;
434 template<typename _Tp>
435 struct __make_unsigned_selector<_Tp, true, false>
438 typedef __make_unsigned<typename remove_cv<_Tp>::type> __unsignedt;
439 typedef typename __unsignedt::__type __unsigned_type;
440 typedef __match_cv_qualifiers<_Tp, __unsigned_type> __cv_unsigned;
443 typedef typename __cv_unsigned::__type __type;
446 template<typename _Tp>
447 struct __make_unsigned_selector<_Tp, false, true>
450 // With -fshort-enums, an enum may be as small as a char.
451 typedef unsigned char __smallest;
452 static const bool __b0 = sizeof(_Tp) <= sizeof(__smallest);
453 static const bool __b1 = sizeof(_Tp) <= sizeof(unsigned short);
454 static const bool __b2 = sizeof(_Tp) <= sizeof(unsigned int);
455 typedef conditional<__b2, unsigned int, unsigned long> __cond2;
456 typedef typename __cond2::type __cond2_type;
457 typedef conditional<__b1, unsigned short, __cond2_type> __cond1;
458 typedef typename __cond1::type __cond1_type;
461 typedef typename conditional<__b0, __smallest, __cond1_type>::type __type;
464 // Given an integral/enum type, return the corresponding unsigned
468 template<typename _Tp>
470 { typedef typename __make_unsigned_selector<_Tp>::__type type; };
472 // Integral, but don't define.
474 struct make_unsigned<bool>;
477 // Utility for finding the signed versions of unsigned integral types.
478 template<typename _Tp>
480 { typedef _Tp __type; };
483 struct __make_signed<char>
484 { typedef signed char __type; };
487 struct __make_signed<unsigned char>
488 { typedef signed char __type; };
491 struct __make_signed<unsigned short>
492 { typedef signed short __type; };
495 struct __make_signed<unsigned int>
496 { typedef signed int __type; };
499 struct __make_signed<unsigned long>
500 { typedef signed long __type; };
503 struct __make_signed<unsigned long long>
504 { typedef signed long long __type; };
507 // Select between integral and enum: not possible to be both.
508 template<typename _Tp,
509 bool _IsInt = is_integral<_Tp>::value,
510 bool _IsEnum = is_enum<_Tp>::value>
511 struct __make_signed_selector;
513 template<typename _Tp>
514 struct __make_signed_selector<_Tp, true, false>
517 typedef __make_signed<typename remove_cv<_Tp>::type> __signedt;
518 typedef typename __signedt::__type __signed_type;
519 typedef __match_cv_qualifiers<_Tp, __signed_type> __cv_signed;
522 typedef typename __cv_signed::__type __type;
525 template<typename _Tp>
526 struct __make_signed_selector<_Tp, false, true>
529 // With -fshort-enums, an enum may be as small as a char.
530 typedef signed char __smallest;
531 static const bool __b0 = sizeof(_Tp) <= sizeof(__smallest);
532 static const bool __b1 = sizeof(_Tp) <= sizeof(signed short);
533 static const bool __b2 = sizeof(_Tp) <= sizeof(signed int);
534 typedef conditional<__b2, signed int, signed long> __cond2;
535 typedef typename __cond2::type __cond2_type;
536 typedef conditional<__b1, signed short, __cond2_type> __cond1;
537 typedef typename __cond1::type __cond1_type;
540 typedef typename conditional<__b0, __smallest, __cond1_type>::type __type;
543 // Given an integral/enum type, return the corresponding signed
547 template<typename _Tp>
549 { typedef typename __make_signed_selector<_Tp>::__type type; };
551 // Integral, but don't define.
553 struct make_signed<bool>;
556 template<typename... _Tp>
559 template<typename _Tp>
560 struct common_type<_Tp>
561 { typedef _Tp type; };
563 template<typename _Tp, typename _Up>
564 struct common_type<_Tp, _Up>
565 { typedef decltype(true ? declval<_Tp>() : declval<_Up>()) type; };
567 template<typename _Tp, typename _Up, typename... _Vp>
568 struct common_type<_Tp, _Up, _Vp...>
571 common_type<typename common_type<_Tp, _Up>::type, _Vp...>::type type;
573 // @} group metaprogramming
576 template<typename _Tp>
577 struct __declval_protector
579 static const bool __stop = false;
580 static typename add_rvalue_reference<_Tp>::type __delegate();
583 template<typename _Tp>
584 inline typename add_rvalue_reference<_Tp>::type
587 static_assert(__declval_protector<_Tp>::__stop,
588 "declval() must not be used!");
589 return __declval_protector<_Tp>::__delegate();
593 #endif // __GXX_EXPERIMENTAL_CXX0X__
595 #endif // _GLIBCXX_TYPE_TRAITS