libstdc++
stl_pair.h
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1 // Pair implementation -*- C++ -*-
2 
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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,
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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
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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
79  _GLIBCXX17_INLINE constexpr piecewise_construct_t piecewise_construct =
80  piecewise_construct_t();
81 
82  // Forward declarations.
83  template<typename...>
84  class tuple;
85 
86  template<std::size_t...>
87  struct _Index_tuple;
88 
89  // Concept utility functions, reused in conditionally-explicit
90  // constructors.
91  // See PR 70437, don't look at is_constructible or
92  // is_convertible if the types are the same to
93  // avoid querying those properties for incomplete types.
94  template <bool, typename _T1, typename _T2>
95  struct _PCC
96  {
97  template <typename _U1, typename _U2>
98  static constexpr bool _ConstructiblePair()
99  {
100  return __and_<is_constructible<_T1, const _U1&>,
101  is_constructible<_T2, const _U2&>>::value;
102  }
103 
104  template <typename _U1, typename _U2>
105  static constexpr bool _ImplicitlyConvertiblePair()
106  {
107  return __and_<is_convertible<const _U1&, _T1>,
108  is_convertible<const _U2&, _T2>>::value;
109  }
110 
111  template <typename _U1, typename _U2>
112  static constexpr bool _MoveConstructiblePair()
113  {
114  return __and_<is_constructible<_T1, _U1&&>,
115  is_constructible<_T2, _U2&&>>::value;
116  }
117 
118  template <typename _U1, typename _U2>
119  static constexpr bool _ImplicitlyMoveConvertiblePair()
120  {
121  return __and_<is_convertible<_U1&&, _T1>,
122  is_convertible<_U2&&, _T2>>::value;
123  }
124 
125  template <bool __implicit, typename _U1, typename _U2>
126  static constexpr bool _CopyMovePair()
127  {
128  using __do_converts = __and_<is_convertible<const _U1&, _T1>,
129  is_convertible<_U2&&, _T2>>;
130  using __converts = typename conditional<__implicit,
131  __do_converts,
132  __not_<__do_converts>>::type;
133  return __and_<is_constructible<_T1, const _U1&>,
134  is_constructible<_T2, _U2&&>,
135  __converts
136  >::value;
137  }
138 
139  template <bool __implicit, typename _U1, typename _U2>
140  static constexpr bool _MoveCopyPair()
141  {
142  using __do_converts = __and_<is_convertible<_U1&&, _T1>,
143  is_convertible<const _U2&, _T2>>;
144  using __converts = typename conditional<__implicit,
145  __do_converts,
146  __not_<__do_converts>>::type;
147  return __and_<is_constructible<_T1, _U1&&>,
148  is_constructible<_T2, const _U2&&>,
149  __converts
150  >::value;
151  }
152  };
153 
154  template <typename _T1, typename _T2>
155  struct _PCC<false, _T1, _T2>
156  {
157  template <typename _U1, typename _U2>
158  static constexpr bool _ConstructiblePair()
159  {
160  return false;
161  }
162 
163  template <typename _U1, typename _U2>
164  static constexpr bool _ImplicitlyConvertiblePair()
165  {
166  return false;
167  }
168 
169  template <typename _U1, typename _U2>
170  static constexpr bool _MoveConstructiblePair()
171  {
172  return false;
173  }
174 
175  template <typename _U1, typename _U2>
176  static constexpr bool _ImplicitlyMoveConvertiblePair()
177  {
178  return false;
179  }
180  };
181 
182  // PR libstdc++/79141, a utility type for preventing
183  // initialization of an argument of a disabled assignment
184  // operator from a pair of empty braces.
185  struct __nonesuch_no_braces : std::__nonesuch {
186  explicit __nonesuch_no_braces(const __nonesuch&) = delete;
187  };
188 
189 #endif
190 
191  /**
192  * @brief Struct holding two objects of arbitrary type.
193  *
194  * @tparam _T1 Type of first object.
195  * @tparam _T2 Type of second object.
196  */
197  template<typename _T1, typename _T2>
198  struct pair
199  {
200  typedef _T1 first_type; /// @c first_type is the first bound type
201  typedef _T2 second_type; /// @c second_type is the second bound type
202 
203  _T1 first; /// @c first is a copy of the first object
204  _T2 second; /// @c second is a copy of the second object
205 
206  // _GLIBCXX_RESOLVE_LIB_DEFECTS
207  // 265. std::pair::pair() effects overly restrictive
208  /** The default constructor creates @c first and @c second using their
209  * respective default constructors. */
210 #if __cplusplus >= 201103L
211  template <typename _U1 = _T1,
212  typename _U2 = _T2,
213  typename enable_if<__and_<
214  __is_implicitly_default_constructible<_U1>,
215  __is_implicitly_default_constructible<_U2>>
216  ::value, bool>::type = true>
217 #endif
218  _GLIBCXX_CONSTEXPR pair()
219  : first(), second() { }
220 
221 #if __cplusplus >= 201103L
222  template <typename _U1 = _T1,
223  typename _U2 = _T2,
224  typename enable_if<__and_<
225  is_default_constructible<_U1>,
226  is_default_constructible<_U2>,
227  __not_<
228  __and_<__is_implicitly_default_constructible<_U1>,
229  __is_implicitly_default_constructible<_U2>>>>
230  ::value, bool>::type = false>
231  explicit constexpr pair()
232  : first(), second() { }
233 #endif
234 
235  /** Two objects may be passed to a @c pair constructor to be copied. */
236 #if __cplusplus < 201103L
237  pair(const _T1& __a, const _T2& __b)
238  : first(__a), second(__b) { }
239 #else
240  // Shortcut for constraining the templates that don't take pairs.
241  using _PCCP = _PCC<true, _T1, _T2>;
242 
243  template<typename _U1 = _T1, typename _U2=_T2, typename
244  enable_if<_PCCP::template
245  _ConstructiblePair<_U1, _U2>()
246  && _PCCP::template
247  _ImplicitlyConvertiblePair<_U1, _U2>(),
248  bool>::type=true>
249  constexpr pair(const _T1& __a, const _T2& __b)
250  : first(__a), second(__b) { }
251 
252  template<typename _U1 = _T1, typename _U2=_T2, typename
253  enable_if<_PCCP::template
254  _ConstructiblePair<_U1, _U2>()
255  && !_PCCP::template
256  _ImplicitlyConvertiblePair<_U1, _U2>(),
257  bool>::type=false>
258  explicit constexpr pair(const _T1& __a, const _T2& __b)
259  : first(__a), second(__b) { }
260 #endif
261 
262  /** There is also a templated copy ctor for the @c pair class itself. */
263 #if __cplusplus < 201103L
264  template<typename _U1, typename _U2>
265  pair(const pair<_U1, _U2>& __p)
266  : first(__p.first), second(__p.second) { }
267 #else
268  // Shortcut for constraining the templates that take pairs.
269  template <typename _U1, typename _U2>
270  using _PCCFP = _PCC<!is_same<_T1, _U1>::value
271  || !is_same<_T2, _U2>::value,
272  _T1, _T2>;
273 
274  template<typename _U1, typename _U2, typename
275  enable_if<_PCCFP<_U1, _U2>::template
276  _ConstructiblePair<_U1, _U2>()
277  && _PCCFP<_U1, _U2>::template
278  _ImplicitlyConvertiblePair<_U1, _U2>(),
279  bool>::type=true>
280  constexpr pair(const pair<_U1, _U2>& __p)
281  : first(__p.first), second(__p.second) { }
282 
283  template<typename _U1, typename _U2, typename
284  enable_if<_PCCFP<_U1, _U2>::template
285  _ConstructiblePair<_U1, _U2>()
286  && !_PCCFP<_U1, _U2>::template
287  _ImplicitlyConvertiblePair<_U1, _U2>(),
288  bool>::type=false>
289  explicit constexpr pair(const pair<_U1, _U2>& __p)
290  : first(__p.first), second(__p.second) { }
291 
292  constexpr pair(const pair&) = default;
293  constexpr pair(pair&&) = default;
294 
295  // DR 811.
296  template<typename _U1, typename
297  enable_if<_PCCP::template
298  _MoveCopyPair<true, _U1, _T2>(),
299  bool>::type=true>
300  constexpr pair(_U1&& __x, const _T2& __y)
301  : first(std::forward<_U1>(__x)), second(__y) { }
302 
303  template<typename _U1, typename
304  enable_if<_PCCP::template
305  _MoveCopyPair<false, _U1, _T2>(),
306  bool>::type=false>
307  explicit constexpr pair(_U1&& __x, const _T2& __y)
308  : first(std::forward<_U1>(__x)), second(__y) { }
309 
310  template<typename _U2, typename
311  enable_if<_PCCP::template
312  _CopyMovePair<true, _T1, _U2>(),
313  bool>::type=true>
314  constexpr pair(const _T1& __x, _U2&& __y)
315  : first(__x), second(std::forward<_U2>(__y)) { }
316 
317  template<typename _U2, typename
318  enable_if<_PCCP::template
319  _CopyMovePair<false, _T1, _U2>(),
320  bool>::type=false>
321  explicit pair(const _T1& __x, _U2&& __y)
322  : first(__x), second(std::forward<_U2>(__y)) { }
323 
324  template<typename _U1, typename _U2, typename
325  enable_if<_PCCP::template
326  _MoveConstructiblePair<_U1, _U2>()
327  && _PCCP::template
328  _ImplicitlyMoveConvertiblePair<_U1, _U2>(),
329  bool>::type=true>
330  constexpr pair(_U1&& __x, _U2&& __y)
331  : first(std::forward<_U1>(__x)), second(std::forward<_U2>(__y)) { }
332 
333  template<typename _U1, typename _U2, typename
334  enable_if<_PCCP::template
335  _MoveConstructiblePair<_U1, _U2>()
336  && !_PCCP::template
337  _ImplicitlyMoveConvertiblePair<_U1, _U2>(),
338  bool>::type=false>
339  explicit constexpr pair(_U1&& __x, _U2&& __y)
340  : first(std::forward<_U1>(__x)), second(std::forward<_U2>(__y)) { }
341 
342 
343  template<typename _U1, typename _U2, typename
344  enable_if<_PCCFP<_U1, _U2>::template
345  _MoveConstructiblePair<_U1, _U2>()
346  && _PCCFP<_U1, _U2>::template
347  _ImplicitlyMoveConvertiblePair<_U1, _U2>(),
348  bool>::type=true>
349  constexpr pair(pair<_U1, _U2>&& __p)
350  : first(std::forward<_U1>(__p.first)),
351  second(std::forward<_U2>(__p.second)) { }
352 
353  template<typename _U1, typename _U2, typename
354  enable_if<_PCCFP<_U1, _U2>::template
355  _MoveConstructiblePair<_U1, _U2>()
356  && !_PCCFP<_U1, _U2>::template
357  _ImplicitlyMoveConvertiblePair<_U1, _U2>(),
358  bool>::type=false>
359  explicit constexpr pair(pair<_U1, _U2>&& __p)
360  : first(std::forward<_U1>(__p.first)),
361  second(std::forward<_U2>(__p.second)) { }
362 
363  template<typename... _Args1, typename... _Args2>
364  pair(piecewise_construct_t, tuple<_Args1...>, tuple<_Args2...>);
365 
366  pair&
367  operator=(typename conditional<
368  __and_<is_copy_assignable<_T1>,
369  is_copy_assignable<_T2>>::value,
370  const pair&, const __nonesuch_no_braces&>::type __p)
371  {
372  first = __p.first;
373  second = __p.second;
374  return *this;
375  }
376 
377  pair&
378  operator=(typename conditional<
379  __not_<__and_<is_copy_assignable<_T1>,
380  is_copy_assignable<_T2>>>::value,
381  const pair&, const __nonesuch_no_braces&>::type __p) = delete;
382 
383  pair&
384  operator=(typename conditional<
385  __and_<is_move_assignable<_T1>,
386  is_move_assignable<_T2>>::value,
387  pair&&, __nonesuch_no_braces&&>::type __p)
388  noexcept(__and_<is_nothrow_move_assignable<_T1>,
389  is_nothrow_move_assignable<_T2>>::value)
390  {
391  first = std::forward<first_type>(__p.first);
392  second = std::forward<second_type>(__p.second);
393  return *this;
394  }
395 
396  template<typename _U1, typename _U2>
397  typename enable_if<__and_<is_assignable<_T1&, const _U1&>,
398  is_assignable<_T2&, const _U2&>>::value,
399  pair&>::type
400  operator=(const pair<_U1, _U2>& __p)
401  {
402  first = __p.first;
403  second = __p.second;
404  return *this;
405  }
406 
407  template<typename _U1, typename _U2>
408  typename enable_if<__and_<is_assignable<_T1&, _U1&&>,
409  is_assignable<_T2&, _U2&&>>::value,
410  pair&>::type
411  operator=(pair<_U1, _U2>&& __p)
412  {
413  first = std::forward<_U1>(__p.first);
414  second = std::forward<_U2>(__p.second);
415  return *this;
416  }
417 
418  void
419  swap(pair& __p)
420  noexcept(__and_<__is_nothrow_swappable<_T1>,
421  __is_nothrow_swappable<_T2>>::value)
422  {
423  using std::swap;
424  swap(first, __p.first);
425  swap(second, __p.second);
426  }
427 
428  private:
429  template<typename... _Args1, std::size_t... _Indexes1,
430  typename... _Args2, std::size_t... _Indexes2>
431  pair(tuple<_Args1...>&, tuple<_Args2...>&,
432  _Index_tuple<_Indexes1...>, _Index_tuple<_Indexes2...>);
433 #endif
434  };
435 
436 #if __cpp_deduction_guides >= 201606
437  template<typename _T1, typename _T2> pair(_T1, _T2) -> pair<_T1, _T2>;
438 #endif
439 
440  /// Two pairs of the same type are equal iff their members are equal.
441  template<typename _T1, typename _T2>
442  inline _GLIBCXX_CONSTEXPR bool
443  operator==(const pair<_T1, _T2>& __x, const pair<_T1, _T2>& __y)
444  { return __x.first == __y.first && __x.second == __y.second; }
445 
446  /// <http://gcc.gnu.org/onlinedocs/libstdc++/manual/utilities.html>
447  template<typename _T1, typename _T2>
448  inline _GLIBCXX_CONSTEXPR bool
449  operator<(const pair<_T1, _T2>& __x, const pair<_T1, _T2>& __y)
450  { return __x.first < __y.first
451  || (!(__y.first < __x.first) && __x.second < __y.second); }
452 
453  /// Uses @c operator== to find the result.
454  template<typename _T1, typename _T2>
455  inline _GLIBCXX_CONSTEXPR bool
456  operator!=(const pair<_T1, _T2>& __x, const pair<_T1, _T2>& __y)
457  { return !(__x == __y); }
458 
459  /// Uses @c operator< to find the result.
460  template<typename _T1, typename _T2>
461  inline _GLIBCXX_CONSTEXPR bool
462  operator>(const pair<_T1, _T2>& __x, const pair<_T1, _T2>& __y)
463  { return __y < __x; }
464 
465  /// Uses @c operator< to find the result.
466  template<typename _T1, typename _T2>
467  inline _GLIBCXX_CONSTEXPR bool
468  operator<=(const pair<_T1, _T2>& __x, const pair<_T1, _T2>& __y)
469  { return !(__y < __x); }
470 
471  /// Uses @c operator< to find the result.
472  template<typename _T1, typename _T2>
473  inline _GLIBCXX_CONSTEXPR bool
474  operator>=(const pair<_T1, _T2>& __x, const pair<_T1, _T2>& __y)
475  { return !(__x < __y); }
476 
477 #if __cplusplus >= 201103L
478  /// See std::pair::swap().
479  // Note: no std::swap overloads in C++03 mode, this has performance
480  // implications, see, eg, libstdc++/38466.
481  template<typename _T1, typename _T2>
482  inline
483 #if __cplusplus > 201402L || !defined(__STRICT_ANSI__) // c++1z or gnu++11
484  // Constrained free swap overload, see p0185r1
485  typename enable_if<__and_<__is_swappable<_T1>,
486  __is_swappable<_T2>>::value>::type
487 #else
488  void
489 #endif
490  swap(pair<_T1, _T2>& __x, pair<_T1, _T2>& __y)
491  noexcept(noexcept(__x.swap(__y)))
492  { __x.swap(__y); }
493 
494 #if __cplusplus > 201402L || !defined(__STRICT_ANSI__) // c++1z or gnu++11
495  template<typename _T1, typename _T2>
496  typename enable_if<!__and_<__is_swappable<_T1>,
497  __is_swappable<_T2>>::value>::type
498  swap(pair<_T1, _T2>&, pair<_T1, _T2>&) = delete;
499 #endif
500 #endif // __cplusplus >= 201103L
501 
502  /**
503  * @brief A convenience wrapper for creating a pair from two objects.
504  * @param __x The first object.
505  * @param __y The second object.
506  * @return A newly-constructed pair<> object of the appropriate type.
507  *
508  * The standard requires that the objects be passed by reference-to-const,
509  * but LWG issue #181 says they should be passed by const value. We follow
510  * the LWG by default.
511  */
512  // _GLIBCXX_RESOLVE_LIB_DEFECTS
513  // 181. make_pair() unintended behavior
514 #if __cplusplus >= 201103L
515  // NB: DR 706.
516  template<typename _T1, typename _T2>
517  constexpr pair<typename __decay_and_strip<_T1>::__type,
518  typename __decay_and_strip<_T2>::__type>
519  make_pair(_T1&& __x, _T2&& __y)
520  {
521  typedef typename __decay_and_strip<_T1>::__type __ds_type1;
522  typedef typename __decay_and_strip<_T2>::__type __ds_type2;
523  typedef pair<__ds_type1, __ds_type2> __pair_type;
524  return __pair_type(std::forward<_T1>(__x), std::forward<_T2>(__y));
525  }
526 #else
527  template<typename _T1, typename _T2>
528  inline pair<_T1, _T2>
529  make_pair(_T1 __x, _T2 __y)
530  { return pair<_T1, _T2>(__x, __y); }
531 #endif
532 
533  /// @}
534 
535 _GLIBCXX_END_NAMESPACE_VERSION
536 } // namespace std
537 
538 #endif /* _STL_PAIR_H */
std::pair::second
_T2 second
first is a copy of the first object
Definition: stl_pair.h:204
std::piecewise_construct
_GLIBCXX17_INLINE constexpr piecewise_construct_t piecewise_construct
piecewise_construct
Definition: stl_pair.h:79
std::tuple
Primary class template, tuple.
Definition: tuple:53
std::pair::pair
constexpr pair()
second is a copy of the second object
Definition: stl_pair.h:218
std::pair::first
_T1 first
second_type is the second bound type
Definition: stl_pair.h:203
std::pair< _BiIter, _BiIter >::_PCCP
_PCC< true, _BiIter, _BiIter > _PCCP
Definition: stl_pair.h:241
std::pair::second_type
_T2 second_type
first_type is the first bound type
Definition: stl_pair.h:201
std
ISO C++ entities toplevel namespace is std.
std::piecewise_construct_t
piecewise_construct_t
Definition: stl_pair.h:76
std::make_pair
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:519
std::pair
Struct holding two objects of arbitrary type.
Definition: stl_pair.h:198
std::pair< _BiIter, _BiIter >::_PCCFP
_PCC<!is_same< _BiIter, _U1 >::value||!is_same< _BiIter, _U2 >::value, _BiIter, _BiIter > _PCCFP
Definition: stl_pair.h:272