libstdc++
stl_pair.h
Go to the documentation of this file.
1 // Pair implementation -*- C++ -*-
2 
3 // Copyright (C) 2001-2016 Free Software Foundation, Inc.
4 //
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)
9 // any later version.
10 
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.
15 
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.
19 
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/>.
24 
25 /*
26  *
27  * Copyright (c) 1994
28  * Hewlett-Packard Company
29  *
30  * Permission to use, copy, modify, distribute and sell this software
31  * and its documentation for any purpose is hereby granted without fee,
32  * provided that the above copyright notice appear in all copies and
33  * that both that copyright notice and this permission notice appear
34  * in supporting documentation. Hewlett-Packard Company makes no
35  * representations about the suitability of this software for any
36  * purpose. It is provided "as is" without express or implied warranty.
37  *
38  *
39  * Copyright (c) 1996,1997
40  * Silicon Graphics Computer Systems, Inc.
41  *
42  * Permission to use, copy, modify, distribute and sell this software
43  * and its documentation for any purpose is hereby granted without fee,
44  * provided that the above copyright notice appear in all copies and
45  * that both that copyright notice and this permission notice appear
46  * in supporting documentation. Silicon Graphics makes no
47  * representations about the suitability of this software for any
48  * purpose. It is provided "as is" without express or implied warranty.
49  */
50 
51 /** @file bits/stl_pair.h
52  * This is an internal header file, included by other library headers.
53  * Do not attempt to use it directly. @headername{utility}
54  */
55 
56 #ifndef _STL_PAIR_H
57 #define _STL_PAIR_H 1
58 
59 #include <bits/move.h> // for std::move / std::forward, and std::swap
60 
61 #if __cplusplus >= 201103L
62 #include <type_traits> // for std::__decay_and_strip too
63 #endif
64 
65 namespace std _GLIBCXX_VISIBILITY(default)
66 {
67 _GLIBCXX_BEGIN_NAMESPACE_VERSION
68 
69  /**
70  * @addtogroup utilities
71  * @{
72  */
73 
74 #if __cplusplus >= 201103L
75  /// piecewise_construct_t
76  struct piecewise_construct_t { explicit piecewise_construct_t() = default; };
77 
78  /// piecewise_construct
80 
81  // Forward declarations.
82  template<typename...>
83  class tuple;
84 
85  template<std::size_t...>
86  struct _Index_tuple;
87 
88  // Concept utility functions, reused in conditionally-explicit
89  // constructors.
90  // See PR 70437, don't look at is_constructible or
91  // is_convertible if the types are the same to
92  // avoid querying those properties for incomplete types.
93  template <bool, typename _T1, typename _T2>
94  struct _PCC
95  {
96  template <typename _U1, typename _U2>
97  static constexpr bool _ConstructiblePair()
98  {
99  return __and_<is_constructible<_T1, const _U1&>,
100  is_constructible<_T2, const _U2&>>::value;
101  }
102 
103  template <typename _U1, typename _U2>
104  static constexpr bool _ImplicitlyConvertiblePair()
105  {
106  return __and_<is_convertible<const _U1&, _T1>,
107  is_convertible<const _U2&, _T2>>::value;
108  }
109 
110  template <typename _U1, typename _U2>
111  static constexpr bool _MoveConstructiblePair()
112  {
113  return __and_<is_constructible<_T1, _U1&&>,
114  is_constructible<_T2, _U2&&>>::value;
115  }
116 
117  template <typename _U1, typename _U2>
118  static constexpr bool _ImplicitlyMoveConvertiblePair()
119  {
120  return __and_<is_convertible<_U1&&, _T1>,
121  is_convertible<_U2&&, _T2>>::value;
122  }
123 
124  template <bool __implicit, typename _U1, typename _U2>
125  static constexpr bool _CopyMovePair()
126  {
127  using __do_converts = __and_<is_convertible<const _U1&, _T1>,
128  is_convertible<_U2&&, _T2>>;
129  using __converts = typename conditional<__implicit,
130  __do_converts,
131  __not_<__do_converts>>::type;
132  return __and_<is_constructible<_T1, const _U1&>,
133  is_constructible<_T2, _U2&&>,
134  __converts
135  >::value;
136  }
137 
138  template <bool __implicit, typename _U1, typename _U2>
139  static constexpr bool _MoveCopyPair()
140  {
141  using __do_converts = __and_<is_convertible<_U1&&, _T1>,
142  is_convertible<const _U2&, _T2>>;
143  using __converts = typename conditional<__implicit,
144  __do_converts,
145  __not_<__do_converts>>::type;
146  return __and_<is_constructible<_T1, _U1&&>,
147  is_constructible<_T2, const _U2&&>,
148  __converts
149  >::value;
150  }
151  };
152 
153  template <typename _T1, typename _T2>
154  struct _PCC<false, _T1, _T2>
155  {
156  template <typename _U1, typename _U2>
157  static constexpr bool _ConstructiblePair()
158  {
159  return false;
160  }
161 
162  template <typename _U1, typename _U2>
163  static constexpr bool _ImplicitlyConvertiblePair()
164  {
165  return false;
166  }
167 
168  template <typename _U1, typename _U2>
169  static constexpr bool _MoveConstructiblePair()
170  {
171  return false;
172  }
173 
174  template <typename _U1, typename _U2>
175  static constexpr bool _ImplicitlyMoveConvertiblePair()
176  {
177  return false;
178  }
179  };
180 
181  struct __wrap_nonesuch : std::__nonesuch {
182  explicit __wrap_nonesuch(const __nonesuch&) = delete;
183  };
184 #endif // C++11
185 
186  template<typename _U1, typename _U2> class __pair_base
187  {
188 #if __cplusplus >= 201103L
189  template<typename _T1, typename _T2> friend struct pair;
190  __pair_base() = default;
191  ~__pair_base() = default;
192  __pair_base(const __pair_base&) = default;
193  __pair_base& operator=(const __pair_base&) = delete;
194 #endif // C++11
195  };
196 
197  /**
198  * @brief Struct holding two objects of arbitrary type.
199  *
200  * @tparam _T1 Type of first object.
201  * @tparam _T2 Type of second object.
202  */
203  template<typename _T1, typename _T2>
204  struct pair
205  : private __pair_base<_T1, _T2>
206  {
207  typedef _T1 first_type; /// @c first_type is the first bound type
208  typedef _T2 second_type; /// @c second_type is the second bound type
209 
210  _T1 first; /// @c first is a copy of the first object
211  _T2 second; /// @c second is a copy of the second object
212 
213  // _GLIBCXX_RESOLVE_LIB_DEFECTS
214  // 265. std::pair::pair() effects overly restrictive
215  /** The default constructor creates @c first and @c second using their
216  * respective default constructors. */
217 #if __cplusplus >= 201103L
218  template <typename _U1 = _T1,
219  typename _U2 = _T2,
220  typename enable_if<__and_<
221  __is_implicitly_default_constructible<_U1>,
222  __is_implicitly_default_constructible<_U2>>
223  ::value, bool>::type = true>
224 #endif
225  _GLIBCXX_CONSTEXPR pair()
226  : first(), second() { }
227 
228 #if __cplusplus >= 201103L
229  template <typename _U1 = _T1,
230  typename _U2 = _T2,
231  typename enable_if<__and_<
232  is_default_constructible<_U1>,
233  is_default_constructible<_U2>,
234  __not_<
235  __and_<__is_implicitly_default_constructible<_U1>,
236  __is_implicitly_default_constructible<_U2>>>>
237  ::value, bool>::type = false>
238  explicit constexpr pair()
239  : first(), second() { }
240 #endif
241 
242  /** Two objects may be passed to a @c pair constructor to be copied. */
243 #if __cplusplus < 201103L
244  pair(const _T1& __a, const _T2& __b)
245  : first(__a), second(__b) { }
246 #else
247  // Shortcut for constraining the templates that don't take pairs.
248  using _PCCP = _PCC<true, _T1, _T2>;
249 
250  template<typename _U1 = _T1, typename _U2=_T2, typename
251  enable_if<_PCCP::template
252  _ConstructiblePair<_U1, _U2>()
253  && _PCCP::template
254  _ImplicitlyConvertiblePair<_U1, _U2>(),
255  bool>::type=true>
256  constexpr pair(const _T1& __a, const _T2& __b)
257  : first(__a), second(__b) { }
258 
259  template<typename _U1 = _T1, typename _U2=_T2, typename
260  enable_if<_PCCP::template
261  _ConstructiblePair<_U1, _U2>()
262  && !_PCCP::template
263  _ImplicitlyConvertiblePair<_U1, _U2>(),
264  bool>::type=false>
265  explicit constexpr pair(const _T1& __a, const _T2& __b)
266  : first(__a), second(__b) { }
267 #endif
268 
269  /** There is also a templated copy ctor for the @c pair class itself. */
270 #if __cplusplus < 201103L
271  template<typename _U1, typename _U2>
272  pair(const pair<_U1, _U2>& __p)
273  : first(__p.first), second(__p.second) { }
274 #else
275  // Shortcut for constraining the templates that take pairs.
276  template <typename _U1, typename _U2>
277  using _PCCFP = _PCC<!is_same<_T1, _U1>::value
278  || !is_same<_T2, _U2>::value,
279  _T1, _T2>;
280 
281  template<typename _U1, typename _U2, typename
282  enable_if<_PCCFP<_U1, _U2>::template
283  _ConstructiblePair<_U1, _U2>()
285  _ImplicitlyConvertiblePair<_U1, _U2>(),
286  bool>::type=true>
287  constexpr pair(const pair<_U1, _U2>& __p)
288  : first(__p.first), second(__p.second) { }
289 
290  template<typename _U1, typename _U2, typename
291  enable_if<_PCCFP<_U1, _U2>::template
292  _ConstructiblePair<_U1, _U2>()
293  && !_PCCFP<_U1, _U2>::template
294  _ImplicitlyConvertiblePair<_U1, _U2>(),
295  bool>::type=false>
296  explicit constexpr pair(const pair<_U1, _U2>& __p)
297  : first(__p.first), second(__p.second) { }
298 
299  constexpr pair(const pair&) = default;
300  constexpr pair(pair&&) = default;
301 
302  // DR 811.
303  template<typename _U1, typename
304  enable_if<_PCCP::template
305  _MoveCopyPair<true, _U1, _T2>(),
306  bool>::type=true>
307  constexpr pair(_U1&& __x, const _T2& __y)
308  : first(std::forward<_U1>(__x)), second(__y) { }
309 
310  template<typename _U1, typename
311  enable_if<_PCCP::template
312  _MoveCopyPair<false, _U1, _T2>(),
313  bool>::type=false>
314  explicit constexpr pair(_U1&& __x, const _T2& __y)
315  : first(std::forward<_U1>(__x)), second(__y) { }
316 
317  template<typename _U2, typename
318  enable_if<_PCCP::template
319  _CopyMovePair<true, _T1, _U2>(),
320  bool>::type=true>
321  constexpr pair(const _T1& __x, _U2&& __y)
322  : first(__x), second(std::forward<_U2>(__y)) { }
323 
324  template<typename _U2, typename
325  enable_if<_PCCP::template
326  _CopyMovePair<false, _T1, _U2>(),
327  bool>::type=false>
328  explicit pair(const _T1& __x, _U2&& __y)
329  : first(__x), second(std::forward<_U2>(__y)) { }
330 
331  template<typename _U1, typename _U2, typename
332  enable_if<_PCCP::template
333  _MoveConstructiblePair<_U1, _U2>()
334  && _PCCP::template
335  _ImplicitlyMoveConvertiblePair<_U1, _U2>(),
336  bool>::type=true>
337  constexpr pair(_U1&& __x, _U2&& __y)
338  : first(std::forward<_U1>(__x)), second(std::forward<_U2>(__y)) { }
339 
340  template<typename _U1, typename _U2, typename
341  enable_if<_PCCP::template
342  _MoveConstructiblePair<_U1, _U2>()
343  && !_PCCP::template
344  _ImplicitlyMoveConvertiblePair<_U1, _U2>(),
345  bool>::type=false>
346  explicit constexpr pair(_U1&& __x, _U2&& __y)
347  : first(std::forward<_U1>(__x)), second(std::forward<_U2>(__y)) { }
348 
349 
350  template<typename _U1, typename _U2, typename
351  enable_if<_PCCFP<_U1, _U2>::template
352  _MoveConstructiblePair<_U1, _U2>()
353  && _PCCFP<_U1, _U2>::template
354  _ImplicitlyMoveConvertiblePair<_U1, _U2>(),
355  bool>::type=true>
356  constexpr pair(pair<_U1, _U2>&& __p)
357  : first(std::forward<_U1>(__p.first)),
358  second(std::forward<_U2>(__p.second)) { }
359 
360  template<typename _U1, typename _U2, typename
361  enable_if<_PCCFP<_U1, _U2>::template
362  _MoveConstructiblePair<_U1, _U2>()
363  && !_PCCFP<_U1, _U2>::template
364  _ImplicitlyMoveConvertiblePair<_U1, _U2>(),
365  bool>::type=false>
366  explicit constexpr pair(pair<_U1, _U2>&& __p)
367  : first(std::forward<_U1>(__p.first)),
368  second(std::forward<_U2>(__p.second)) { }
369 
370  template<typename... _Args1, typename... _Args2>
371  pair(piecewise_construct_t, tuple<_Args1...>, tuple<_Args2...>);
372 
373  pair&
374  operator=(typename conditional<
375  __and_<is_copy_assignable<_T1>,
376  is_copy_assignable<_T2>>::value,
377  const pair&, const __wrap_nonesuch&>::type __p)
378  {
379  first = __p.first;
380  second = __p.second;
381  return *this;
382  }
383 
384  pair&
385  operator=(typename conditional<
386  __and_<is_move_assignable<_T1>,
387  is_move_assignable<_T2>>::value,
388  pair&&, __wrap_nonesuch&&>::type __p)
389  noexcept(__and_<is_nothrow_move_assignable<_T1>,
390  is_nothrow_move_assignable<_T2>>::value)
391  {
392  first = std::forward<first_type>(__p.first);
393  second = std::forward<second_type>(__p.second);
394  return *this;
395  }
396 
397  template<typename _U1, typename _U2>
398  typename enable_if<__and_<is_assignable<_T1&, const _U1&>,
399  is_assignable<_T2&, const _U2&>>::value,
400  pair&>::type
401  operator=(const pair<_U1, _U2>& __p)
402  {
403  first = __p.first;
404  second = __p.second;
405  return *this;
406  }
407 
408  template<typename _U1, typename _U2>
409  typename enable_if<__and_<is_assignable<_T1&, _U1&&>,
410  is_assignable<_T2&, _U2&&>>::value,
411  pair&>::type
412  operator=(pair<_U1, _U2>&& __p)
413  {
414  first = std::forward<_U1>(__p.first);
415  second = std::forward<_U2>(__p.second);
416  return *this;
417  }
418 
419  void
420  swap(pair& __p)
421  noexcept(__is_nothrow_swappable<_T1>::value
422  && __is_nothrow_swappable<_T2>::value)
423  {
424  using std::swap;
425  swap(first, __p.first);
426  swap(second, __p.second);
427  }
428 
429  private:
430  template<typename... _Args1, std::size_t... _Indexes1,
431  typename... _Args2, std::size_t... _Indexes2>
432  pair(tuple<_Args1...>&, tuple<_Args2...>&,
433  _Index_tuple<_Indexes1...>, _Index_tuple<_Indexes2...>);
434 #endif
435  };
436 
437  /// Two pairs of the same type are equal iff their members are equal.
438  template<typename _T1, typename _T2>
439  inline _GLIBCXX_CONSTEXPR bool
440  operator==(const pair<_T1, _T2>& __x, const pair<_T1, _T2>& __y)
441  { return __x.first == __y.first && __x.second == __y.second; }
442 
443  /// <http://gcc.gnu.org/onlinedocs/libstdc++/manual/utilities.html>
444  template<typename _T1, typename _T2>
445  inline _GLIBCXX_CONSTEXPR bool
446  operator<(const pair<_T1, _T2>& __x, const pair<_T1, _T2>& __y)
447  { return __x.first < __y.first
448  || (!(__y.first < __x.first) && __x.second < __y.second); }
449 
450  /// Uses @c operator== to find the result.
451  template<typename _T1, typename _T2>
452  inline _GLIBCXX_CONSTEXPR bool
453  operator!=(const pair<_T1, _T2>& __x, const pair<_T1, _T2>& __y)
454  { return !(__x == __y); }
455 
456  /// Uses @c operator< to find the result.
457  template<typename _T1, typename _T2>
458  inline _GLIBCXX_CONSTEXPR bool
459  operator>(const pair<_T1, _T2>& __x, const pair<_T1, _T2>& __y)
460  { return __y < __x; }
461 
462  /// Uses @c operator< to find the result.
463  template<typename _T1, typename _T2>
464  inline _GLIBCXX_CONSTEXPR bool
465  operator<=(const pair<_T1, _T2>& __x, const pair<_T1, _T2>& __y)
466  { return !(__y < __x); }
467 
468  /// Uses @c operator< to find the result.
469  template<typename _T1, typename _T2>
470  inline _GLIBCXX_CONSTEXPR bool
471  operator>=(const pair<_T1, _T2>& __x, const pair<_T1, _T2>& __y)
472  { return !(__x < __y); }
473 
474 #if __cplusplus >= 201103L
475  /// See std::pair::swap().
476  // Note: no std::swap overloads in C++03 mode, this has performance
477  // implications, see, eg, libstdc++/38466.
478  template<typename _T1, typename _T2>
479  inline void
481  noexcept(noexcept(__x.swap(__y)))
482  { __x.swap(__y); }
483 #endif
484 
485  /**
486  * @brief A convenience wrapper for creating a pair from two objects.
487  * @param __x The first object.
488  * @param __y The second object.
489  * @return A newly-constructed pair<> object of the appropriate type.
490  *
491  * The standard requires that the objects be passed by reference-to-const,
492  * but LWG issue #181 says they should be passed by const value. We follow
493  * the LWG by default.
494  */
495  // _GLIBCXX_RESOLVE_LIB_DEFECTS
496  // 181. make_pair() unintended behavior
497 #if __cplusplus >= 201103L
498  // NB: DR 706.
499  template<typename _T1, typename _T2>
500  constexpr pair<typename __decay_and_strip<_T1>::__type,
501  typename __decay_and_strip<_T2>::__type>
502  make_pair(_T1&& __x, _T2&& __y)
503  {
504  typedef typename __decay_and_strip<_T1>::__type __ds_type1;
505  typedef typename __decay_and_strip<_T2>::__type __ds_type2;
506  typedef pair<__ds_type1, __ds_type2> __pair_type;
507  return __pair_type(std::forward<_T1>(__x), std::forward<_T2>(__y));
508  }
509 #else
510  template<typename _T1, typename _T2>
511  inline pair<_T1, _T2>
512  make_pair(_T1 __x, _T2 __y)
513  { return pair<_T1, _T2>(__x, __y); }
514 #endif
515 
516  /// @}
517 
518 _GLIBCXX_END_NAMESPACE_VERSION
519 } // namespace std
520 
521 #endif /* _STL_PAIR_H */
constexpr _Tp && forward(typename std::remove_reference< _Tp >::type &__t) noexcept
Forward an lvalue.
Definition: move.h:76
constexpr pair()
second is a copy of the second object
Definition: stl_pair.h:225
_T1 first
second_type is the second bound type
Definition: stl_pair.h:210
_T2 second_type
first_type is the first bound type
Definition: stl_pair.h:208
_PCC<!is_same< _T1, _U1 >::value||!is_same< _T2, _U2 >::value, _T1, _T2 > _PCCFP
Definition: stl_pair.h:279
Struct holding two objects of arbitrary type.
Definition: stl_pair.h:204
piecewise_construct_t
Definition: stl_pair.h:76
Primary class template, tuple.
Definition: tuple:461
_PCC< true, _BiIter, _BiIter > _PCCP
Definition: stl_pair.h:248
constexpr piecewise_construct_t piecewise_construct
piecewise_construct
Definition: stl_pair.h:79
constexpr pair< typename __decay_and_strip< _T1 >::__type, typename __decay_and_strip< _T2 >::__type > make_pair(_T1 &&__x, _T2 &&__y)
A convenience wrapper for creating a pair from two objects.
Definition: stl_pair.h:502
_T2 second
first is a copy of the first object
Definition: stl_pair.h:211