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
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38  *
39  * Copyright (c) 1996,1997
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41  *
42  * Permission to use, copy, modify, distribute and sell this software
43  * and its documentation for any purpose is hereby granted without fee,
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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 #endif // C++11
189 
190  template<typename _U1, typename _U2> class __pair_base
191  {
192 #if __cplusplus >= 201103L
193  template<typename _T1, typename _T2> friend struct pair;
194  __pair_base() = default;
195  ~__pair_base() = default;
196  __pair_base(const __pair_base&) = default;
197  __pair_base& operator=(const __pair_base&) = delete;
198 #endif // C++11
199  };
200 
201  /**
202  * @brief Struct holding two objects of arbitrary type.
203  *
204  * @tparam _T1 Type of first object.
205  * @tparam _T2 Type of second object.
206  */
207  template<typename _T1, typename _T2>
208  struct pair
209  : private __pair_base<_T1, _T2>
210  {
211  typedef _T1 first_type; /// @c first_type is the first bound type
212  typedef _T2 second_type; /// @c second_type is the second bound type
213 
214  _T1 first; /// @c first is a copy of the first object
215  _T2 second; /// @c second is a copy of the second object
216 
217  // _GLIBCXX_RESOLVE_LIB_DEFECTS
218  // 265. std::pair::pair() effects overly restrictive
219  /** The default constructor creates @c first and @c second using their
220  * respective default constructors. */
221 #if __cplusplus >= 201103L
222  template <typename _U1 = _T1,
223  typename _U2 = _T2,
224  typename enable_if<__and_<
225  __is_implicitly_default_constructible<_U1>,
226  __is_implicitly_default_constructible<_U2>>
227  ::value, bool>::type = true>
228 #endif
229  _GLIBCXX_CONSTEXPR pair()
230  : first(), second() { }
231 
232 #if __cplusplus >= 201103L
233  template <typename _U1 = _T1,
234  typename _U2 = _T2,
235  typename enable_if<__and_<
236  is_default_constructible<_U1>,
237  is_default_constructible<_U2>,
238  __not_<
239  __and_<__is_implicitly_default_constructible<_U1>,
240  __is_implicitly_default_constructible<_U2>>>>
241  ::value, bool>::type = false>
242  explicit constexpr pair()
243  : first(), second() { }
244 #endif
245 
246  /** Two objects may be passed to a @c pair constructor to be copied. */
247 #if __cplusplus < 201103L
248  pair(const _T1& __a, const _T2& __b)
249  : first(__a), second(__b) { }
250 #else
251  // Shortcut for constraining the templates that don't take pairs.
252  using _PCCP = _PCC<true, _T1, _T2>;
253 
254  template<typename _U1 = _T1, typename _U2=_T2, typename
255  enable_if<_PCCP::template
256  _ConstructiblePair<_U1, _U2>()
257  && _PCCP::template
258  _ImplicitlyConvertiblePair<_U1, _U2>(),
259  bool>::type=true>
260  constexpr pair(const _T1& __a, const _T2& __b)
261  : first(__a), second(__b) { }
262 
263  template<typename _U1 = _T1, typename _U2=_T2, typename
264  enable_if<_PCCP::template
265  _ConstructiblePair<_U1, _U2>()
266  && !_PCCP::template
267  _ImplicitlyConvertiblePair<_U1, _U2>(),
268  bool>::type=false>
269  explicit constexpr pair(const _T1& __a, const _T2& __b)
270  : first(__a), second(__b) { }
271 #endif
272 
273  /** There is also a templated copy ctor for the @c pair class itself. */
274 #if __cplusplus < 201103L
275  template<typename _U1, typename _U2>
276  pair(const pair<_U1, _U2>& __p)
277  : first(__p.first), second(__p.second) { }
278 #else
279  // Shortcut for constraining the templates that take pairs.
280  template <typename _U1, typename _U2>
281  using _PCCFP = _PCC<!is_same<_T1, _U1>::value
282  || !is_same<_T2, _U2>::value,
283  _T1, _T2>;
284 
285  template<typename _U1, typename _U2, typename
286  enable_if<_PCCFP<_U1, _U2>::template
287  _ConstructiblePair<_U1, _U2>()
288  && _PCCFP<_U1, _U2>::template
289  _ImplicitlyConvertiblePair<_U1, _U2>(),
290  bool>::type=true>
291  constexpr pair(const pair<_U1, _U2>& __p)
292  : first(__p.first), second(__p.second) { }
293 
294  template<typename _U1, typename _U2, typename
295  enable_if<_PCCFP<_U1, _U2>::template
296  _ConstructiblePair<_U1, _U2>()
297  && !_PCCFP<_U1, _U2>::template
298  _ImplicitlyConvertiblePair<_U1, _U2>(),
299  bool>::type=false>
300  explicit constexpr pair(const pair<_U1, _U2>& __p)
301  : first(__p.first), second(__p.second) { }
302 
303  constexpr pair(const pair&) = default;
304  constexpr pair(pair&&) = default;
305 
306  // DR 811.
307  template<typename _U1, typename
308  enable_if<_PCCP::template
309  _MoveCopyPair<true, _U1, _T2>(),
310  bool>::type=true>
311  constexpr pair(_U1&& __x, const _T2& __y)
312  : first(std::forward<_U1>(__x)), second(__y) { }
313 
314  template<typename _U1, typename
315  enable_if<_PCCP::template
316  _MoveCopyPair<false, _U1, _T2>(),
317  bool>::type=false>
318  explicit constexpr pair(_U1&& __x, const _T2& __y)
319  : first(std::forward<_U1>(__x)), second(__y) { }
320 
321  template<typename _U2, typename
322  enable_if<_PCCP::template
323  _CopyMovePair<true, _T1, _U2>(),
324  bool>::type=true>
325  constexpr pair(const _T1& __x, _U2&& __y)
326  : first(__x), second(std::forward<_U2>(__y)) { }
327 
328  template<typename _U2, typename
329  enable_if<_PCCP::template
330  _CopyMovePair<false, _T1, _U2>(),
331  bool>::type=false>
332  explicit pair(const _T1& __x, _U2&& __y)
333  : first(__x), second(std::forward<_U2>(__y)) { }
334 
335  template<typename _U1, typename _U2, typename
336  enable_if<_PCCP::template
337  _MoveConstructiblePair<_U1, _U2>()
338  && _PCCP::template
339  _ImplicitlyMoveConvertiblePair<_U1, _U2>(),
340  bool>::type=true>
341  constexpr pair(_U1&& __x, _U2&& __y)
342  : first(std::forward<_U1>(__x)), second(std::forward<_U2>(__y)) { }
343 
344  template<typename _U1, typename _U2, typename
345  enable_if<_PCCP::template
346  _MoveConstructiblePair<_U1, _U2>()
347  && !_PCCP::template
348  _ImplicitlyMoveConvertiblePair<_U1, _U2>(),
349  bool>::type=false>
350  explicit constexpr pair(_U1&& __x, _U2&& __y)
351  : first(std::forward<_U1>(__x)), second(std::forward<_U2>(__y)) { }
352 
353 
354  template<typename _U1, typename _U2, typename
355  enable_if<_PCCFP<_U1, _U2>::template
356  _MoveConstructiblePair<_U1, _U2>()
357  && _PCCFP<_U1, _U2>::template
358  _ImplicitlyMoveConvertiblePair<_U1, _U2>(),
359  bool>::type=true>
360  constexpr pair(pair<_U1, _U2>&& __p)
361  : first(std::forward<_U1>(__p.first)),
362  second(std::forward<_U2>(__p.second)) { }
363 
364  template<typename _U1, typename _U2, typename
365  enable_if<_PCCFP<_U1, _U2>::template
366  _MoveConstructiblePair<_U1, _U2>()
367  && !_PCCFP<_U1, _U2>::template
368  _ImplicitlyMoveConvertiblePair<_U1, _U2>(),
369  bool>::type=false>
370  explicit constexpr pair(pair<_U1, _U2>&& __p)
371  : first(std::forward<_U1>(__p.first)),
372  second(std::forward<_U2>(__p.second)) { }
373 
374  template<typename... _Args1, typename... _Args2>
375  pair(piecewise_construct_t, tuple<_Args1...>, tuple<_Args2...>);
376 
377  pair&
378  operator=(typename conditional<
379  __and_<is_copy_assignable<_T1>,
380  is_copy_assignable<_T2>>::value,
381  const pair&, const __nonesuch_no_braces&>::type __p)
382  {
383  first = __p.first;
384  second = __p.second;
385  return *this;
386  }
387 
388  pair&
389  operator=(typename conditional<
390  __and_<is_move_assignable<_T1>,
391  is_move_assignable<_T2>>::value,
392  pair&&, __nonesuch_no_braces&&>::type __p)
393  noexcept(__and_<is_nothrow_move_assignable<_T1>,
394  is_nothrow_move_assignable<_T2>>::value)
395  {
396  first = std::forward<first_type>(__p.first);
397  second = std::forward<second_type>(__p.second);
398  return *this;
399  }
400 
401  template<typename _U1, typename _U2>
402  typename enable_if<__and_<is_assignable<_T1&, const _U1&>,
403  is_assignable<_T2&, const _U2&>>::value,
404  pair&>::type
405  operator=(const pair<_U1, _U2>& __p)
406  {
407  first = __p.first;
408  second = __p.second;
409  return *this;
410  }
411 
412  template<typename _U1, typename _U2>
413  typename enable_if<__and_<is_assignable<_T1&, _U1&&>,
414  is_assignable<_T2&, _U2&&>>::value,
415  pair&>::type
416  operator=(pair<_U1, _U2>&& __p)
417  {
418  first = std::forward<_U1>(__p.first);
419  second = std::forward<_U2>(__p.second);
420  return *this;
421  }
422 
423  void
424  swap(pair& __p)
425  noexcept(__and_<__is_nothrow_swappable<_T1>,
426  __is_nothrow_swappable<_T2>>::value)
427  {
428  using std::swap;
429  swap(first, __p.first);
430  swap(second, __p.second);
431  }
432 
433  private:
434  template<typename... _Args1, std::size_t... _Indexes1,
435  typename... _Args2, std::size_t... _Indexes2>
436  pair(tuple<_Args1...>&, tuple<_Args2...>&,
437  _Index_tuple<_Indexes1...>, _Index_tuple<_Indexes2...>);
438 #endif
439  };
440 
441 #if __cpp_deduction_guides >= 201606
442  template<typename _T1, typename _T2> pair(_T1, _T2) -> pair<_T1, _T2>;
443 #endif
444 
445  /// Two pairs of the same type are equal iff their members are equal.
446  template<typename _T1, typename _T2>
447  inline _GLIBCXX_CONSTEXPR bool
448  operator==(const pair<_T1, _T2>& __x, const pair<_T1, _T2>& __y)
449  { return __x.first == __y.first && __x.second == __y.second; }
450 
451  /// <http://gcc.gnu.org/onlinedocs/libstdc++/manual/utilities.html>
452  template<typename _T1, typename _T2>
453  inline _GLIBCXX_CONSTEXPR bool
454  operator<(const pair<_T1, _T2>& __x, const pair<_T1, _T2>& __y)
455  { return __x.first < __y.first
456  || (!(__y.first < __x.first) && __x.second < __y.second); }
457 
458  /// Uses @c operator== to find the result.
459  template<typename _T1, typename _T2>
460  inline _GLIBCXX_CONSTEXPR bool
461  operator!=(const pair<_T1, _T2>& __x, const pair<_T1, _T2>& __y)
462  { return !(__x == __y); }
463 
464  /// Uses @c operator< to find the result.
465  template<typename _T1, typename _T2>
466  inline _GLIBCXX_CONSTEXPR bool
467  operator>(const pair<_T1, _T2>& __x, const pair<_T1, _T2>& __y)
468  { return __y < __x; }
469 
470  /// Uses @c operator< to find the result.
471  template<typename _T1, typename _T2>
472  inline _GLIBCXX_CONSTEXPR bool
473  operator<=(const pair<_T1, _T2>& __x, const pair<_T1, _T2>& __y)
474  { return !(__y < __x); }
475 
476  /// Uses @c operator< to find the result.
477  template<typename _T1, typename _T2>
478  inline _GLIBCXX_CONSTEXPR bool
479  operator>=(const pair<_T1, _T2>& __x, const pair<_T1, _T2>& __y)
480  { return !(__x < __y); }
481 
482 #if __cplusplus >= 201103L
483  /// See std::pair::swap().
484  // Note: no std::swap overloads in C++03 mode, this has performance
485  // implications, see, eg, libstdc++/38466.
486  template<typename _T1, typename _T2>
487  inline
488 #if __cplusplus > 201402L || !defined(__STRICT_ANSI__) // c++1z or gnu++11
489  // Constrained free swap overload, see p0185r1
490  typename enable_if<__and_<__is_swappable<_T1>,
491  __is_swappable<_T2>>::value>::type
492 #else
493  void
494 #endif
495  swap(pair<_T1, _T2>& __x, pair<_T1, _T2>& __y)
496  noexcept(noexcept(__x.swap(__y)))
497  { __x.swap(__y); }
498 
499 #if __cplusplus > 201402L || !defined(__STRICT_ANSI__) // c++1z or gnu++11
500  template<typename _T1, typename _T2>
501  typename enable_if<!__and_<__is_swappable<_T1>,
502  __is_swappable<_T2>>::value>::type
503  swap(pair<_T1, _T2>&, pair<_T1, _T2>&) = delete;
504 #endif
505 #endif // __cplusplus >= 201103L
506 
507  /**
508  * @brief A convenience wrapper for creating a pair from two objects.
509  * @param __x The first object.
510  * @param __y The second object.
511  * @return A newly-constructed pair<> object of the appropriate type.
512  *
513  * The standard requires that the objects be passed by reference-to-const,
514  * but LWG issue #181 says they should be passed by const value. We follow
515  * the LWG by default.
516  */
517  // _GLIBCXX_RESOLVE_LIB_DEFECTS
518  // 181. make_pair() unintended behavior
519 #if __cplusplus >= 201103L
520  // NB: DR 706.
521  template<typename _T1, typename _T2>
522  constexpr pair<typename __decay_and_strip<_T1>::__type,
523  typename __decay_and_strip<_T2>::__type>
524  make_pair(_T1&& __x, _T2&& __y)
525  {
526  typedef typename __decay_and_strip<_T1>::__type __ds_type1;
527  typedef typename __decay_and_strip<_T2>::__type __ds_type2;
528  typedef pair<__ds_type1, __ds_type2> __pair_type;
529  return __pair_type(std::forward<_T1>(__x), std::forward<_T2>(__y));
530  }
531 #else
532  template<typename _T1, typename _T2>
533  inline pair<_T1, _T2>
534  make_pair(_T1 __x, _T2 __y)
535  { return pair<_T1, _T2>(__x, __y); }
536 #endif
537 
538  /// @}
539 
540 _GLIBCXX_END_NAMESPACE_VERSION
541 } // namespace std
542 
543 #endif /* _STL_PAIR_H */
std::pair
Struct holding two objects of arbitrary type.
Definition: stl_pair.h:208
std::enable_if
Define a member typedef type only if a boolean constant is true.
Definition: type_traits:1913
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:524
std::is_default_constructible
is_default_constructible
Definition: type_traits:878
std
ISO C++ entities toplevel namespace is std.
std::is_constructible
is_constructible
Definition: type_traits:872
std::pair< _BiIter, _BiIter >::_PCCP
_PCC< true, _BiIter, _BiIter > _PCCP
Definition: stl_pair.h:252
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:229
std::forward
constexpr _Tp && forward(typename std::remove_reference< _Tp >::type &__t) noexcept
Forward an lvalue.
Definition: move.h:74
std::pair::second_type
_T2 second_type
first_type is the first bound type
Definition: stl_pair.h:212
std::pair::first
_T1 first
second_type is the second bound type
Definition: stl_pair.h:214
std::piecewise_construct
_GLIBCXX17_INLINE constexpr piecewise_construct_t piecewise_construct
piecewise_construct
Definition: stl_pair.h:79
std::pair::second
_T2 second
first is a copy of the first object
Definition: stl_pair.h:215
std::piecewise_construct_t
piecewise_construct_t
Definition: stl_pair.h:76
std::pair::_PCCFP
_PCC<!is_same< _T1, _U1 >::value||!is_same< _T2, _U2 >::value, _T1, _T2 > _PCCFP
Definition: stl_pair.h:283