libstdc++
stl_pair.h
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1 // Pair implementation -*- C++ -*-
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24 
25 /*
26  *
27  * Copyright (c) 1994
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29  *
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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  constexpr piecewise_construct_t piecewise_construct = piecewise_construct_t();
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 #endif
182 
183  /**
184  * @brief Struct holding two objects of arbitrary type.
185  *
186  * @tparam _T1 Type of first object.
187  * @tparam _T2 Type of second object.
188  */
189  template<typename _T1, typename _T2>
190  struct pair
191  {
192  typedef _T1 first_type; /// @c first_type is the first bound type
193  typedef _T2 second_type; /// @c second_type is the second bound type
194 
195  _T1 first; /// @c first is a copy of the first object
196  _T2 second; /// @c second is a copy of the second object
197 
198  // _GLIBCXX_RESOLVE_LIB_DEFECTS
199  // 265. std::pair::pair() effects overly restrictive
200  /** The default constructor creates @c first and @c second using their
201  * respective default constructors. */
202 #if __cplusplus >= 201103L
203  template <typename _U1 = _T1,
204  typename _U2 = _T2,
205  typename enable_if<__and_<
206  __is_implicitly_default_constructible<_U1>,
207  __is_implicitly_default_constructible<_U2>>
208  ::value, bool>::type = true>
209 #endif
210  _GLIBCXX_CONSTEXPR pair()
211  : first(), second() { }
212 
213 #if __cplusplus >= 201103L
214  template <typename _U1 = _T1,
215  typename _U2 = _T2,
216  typename enable_if<__and_<
217  is_default_constructible<_U1>,
218  is_default_constructible<_U2>,
219  __not_<
220  __and_<__is_implicitly_default_constructible<_U1>,
221  __is_implicitly_default_constructible<_U2>>>>
222  ::value, bool>::type = false>
223  explicit constexpr pair()
224  : first(), second() { }
225 #endif
226 
227  /** Two objects may be passed to a @c pair constructor to be copied. */
228 #if __cplusplus < 201103L
229  pair(const _T1& __a, const _T2& __b)
230  : first(__a), second(__b) { }
231 #else
232  // Shortcut for constraining the templates that don't take pairs.
233  using _PCCP = _PCC<true, _T1, _T2>;
234 
235  template<typename _U1 = _T1, typename _U2=_T2, typename
236  enable_if<_PCCP::template
237  _ConstructiblePair<_U1, _U2>()
238  && _PCCP::template
239  _ImplicitlyConvertiblePair<_U1, _U2>(),
240  bool>::type=true>
241  constexpr pair(const _T1& __a, const _T2& __b)
242  : first(__a), second(__b) { }
243 
244  template<typename _U1 = _T1, typename _U2=_T2, typename
245  enable_if<_PCCP::template
246  _ConstructiblePair<_U1, _U2>()
247  && !_PCCP::template
248  _ImplicitlyConvertiblePair<_U1, _U2>(),
249  bool>::type=false>
250  explicit constexpr pair(const _T1& __a, const _T2& __b)
251  : first(__a), second(__b) { }
252 #endif
253 
254  /** There is also a templated copy ctor for the @c pair class itself. */
255 #if __cplusplus < 201103L
256  template<typename _U1, typename _U2>
257  pair(const pair<_U1, _U2>& __p)
258  : first(__p.first), second(__p.second) { }
259 #else
260  // Shortcut for constraining the templates that take pairs.
261  template <typename _U1, typename _U2>
262  using _PCCFP = _PCC<!is_same<_T1, _U1>::value
263  || !is_same<_T2, _U2>::value,
264  _T1, _T2>;
265 
266  template<typename _U1, typename _U2, typename
267  enable_if<_PCCFP<_U1, _U2>::template
268  _ConstructiblePair<_U1, _U2>()
269  && _PCCFP<_U1, _U2>::template
270  _ImplicitlyConvertiblePair<_U1, _U2>(),
271  bool>::type=true>
272  constexpr pair(const pair<_U1, _U2>& __p)
273  : first(__p.first), second(__p.second) { }
274 
275  template<typename _U1, typename _U2, typename
276  enable_if<_PCCFP<_U1, _U2>::template
277  _ConstructiblePair<_U1, _U2>()
278  && !_PCCFP<_U1, _U2>::template
279  _ImplicitlyConvertiblePair<_U1, _U2>(),
280  bool>::type=false>
281  explicit constexpr pair(const pair<_U1, _U2>& __p)
282  : first(__p.first), second(__p.second) { }
283 
284  constexpr pair(const pair&) = default;
285  constexpr pair(pair&&) = default;
286 
287  // DR 811.
288  template<typename _U1, typename
289  enable_if<_PCCP::template
290  _MoveCopyPair<true, _U1, _T2>(),
291  bool>::type=true>
292  constexpr pair(_U1&& __x, const _T2& __y)
293  : first(std::forward<_U1>(__x)), second(__y) { }
294 
295  template<typename _U1, typename
296  enable_if<_PCCP::template
297  _MoveCopyPair<false, _U1, _T2>(),
298  bool>::type=false>
299  explicit constexpr pair(_U1&& __x, const _T2& __y)
300  : first(std::forward<_U1>(__x)), second(__y) { }
301 
302  template<typename _U2, typename
303  enable_if<_PCCP::template
304  _CopyMovePair<true, _T1, _U2>(),
305  bool>::type=true>
306  constexpr pair(const _T1& __x, _U2&& __y)
307  : first(__x), second(std::forward<_U2>(__y)) { }
308 
309  template<typename _U2, typename
310  enable_if<_PCCP::template
311  _CopyMovePair<false, _T1, _U2>(),
312  bool>::type=false>
313  explicit pair(const _T1& __x, _U2&& __y)
314  : first(__x), second(std::forward<_U2>(__y)) { }
315 
316  template<typename _U1, typename _U2, typename
317  enable_if<_PCCP::template
318  _MoveConstructiblePair<_U1, _U2>()
319  && _PCCP::template
320  _ImplicitlyMoveConvertiblePair<_U1, _U2>(),
321  bool>::type=true>
322  constexpr pair(_U1&& __x, _U2&& __y)
323  : first(std::forward<_U1>(__x)), second(std::forward<_U2>(__y)) { }
324 
325  template<typename _U1, typename _U2, typename
326  enable_if<_PCCP::template
327  _MoveConstructiblePair<_U1, _U2>()
328  && !_PCCP::template
329  _ImplicitlyMoveConvertiblePair<_U1, _U2>(),
330  bool>::type=false>
331  explicit constexpr pair(_U1&& __x, _U2&& __y)
332  : first(std::forward<_U1>(__x)), second(std::forward<_U2>(__y)) { }
333 
334 
335  template<typename _U1, typename _U2, typename
336  enable_if<_PCCFP<_U1, _U2>::template
337  _MoveConstructiblePair<_U1, _U2>()
338  && _PCCFP<_U1, _U2>::template
339  _ImplicitlyMoveConvertiblePair<_U1, _U2>(),
340  bool>::type=true>
341  constexpr pair(pair<_U1, _U2>&& __p)
342  : first(std::forward<_U1>(__p.first)),
343  second(std::forward<_U2>(__p.second)) { }
344 
345  template<typename _U1, typename _U2, typename
346  enable_if<_PCCFP<_U1, _U2>::template
347  _MoveConstructiblePair<_U1, _U2>()
348  && !_PCCFP<_U1, _U2>::template
349  _ImplicitlyMoveConvertiblePair<_U1, _U2>(),
350  bool>::type=false>
351  explicit constexpr pair(pair<_U1, _U2>&& __p)
352  : first(std::forward<_U1>(__p.first)),
353  second(std::forward<_U2>(__p.second)) { }
354 
355  template<typename... _Args1, typename... _Args2>
356  pair(piecewise_construct_t, tuple<_Args1...>, tuple<_Args2...>);
357 
358  pair&
359  operator=(typename conditional<
360  __and_<is_copy_assignable<_T1>,
361  is_copy_assignable<_T2>>::value,
362  const pair&, const __nonesuch&>::type __p)
363  {
364  first = __p.first;
365  second = __p.second;
366  return *this;
367  }
368 
369  pair&
370  operator=(typename conditional<
371  __not_<__and_<is_copy_assignable<_T1>,
372  is_copy_assignable<_T2>>>::value,
373  const pair&, const __nonesuch&>::type __p) = delete;
374 
375  pair&
376  operator=(typename conditional<
377  __and_<is_move_assignable<_T1>,
378  is_move_assignable<_T2>>::value,
379  pair&&, __nonesuch&&>::type __p)
380  noexcept(__and_<is_nothrow_move_assignable<_T1>,
381  is_nothrow_move_assignable<_T2>>::value)
382  {
383  first = std::forward<first_type>(__p.first);
384  second = std::forward<second_type>(__p.second);
385  return *this;
386  }
387 
388  template<typename _U1, typename _U2>
389  typename enable_if<__and_<is_assignable<_T1&, const _U1&>,
390  is_assignable<_T2&, const _U2&>>::value,
391  pair&>::type
392  operator=(const pair<_U1, _U2>& __p)
393  {
394  first = __p.first;
395  second = __p.second;
396  return *this;
397  }
398 
399  template<typename _U1, typename _U2>
400  typename enable_if<__and_<is_assignable<_T1&, _U1&&>,
401  is_assignable<_T2&, _U2&&>>::value,
402  pair&>::type
403  operator=(pair<_U1, _U2>&& __p)
404  {
405  first = std::forward<_U1>(__p.first);
406  second = std::forward<_U2>(__p.second);
407  return *this;
408  }
409 
410  void
411  swap(pair& __p)
412  noexcept(__is_nothrow_swappable<_T1>::value
413  && __is_nothrow_swappable<_T2>::value)
414  {
415  using std::swap;
416  swap(first, __p.first);
417  swap(second, __p.second);
418  }
419 
420  private:
421  template<typename... _Args1, std::size_t... _Indexes1,
422  typename... _Args2, std::size_t... _Indexes2>
423  pair(tuple<_Args1...>&, tuple<_Args2...>&,
424  _Index_tuple<_Indexes1...>, _Index_tuple<_Indexes2...>);
425 #endif
426  };
427 
428  /// Two pairs of the same type are equal iff their members are equal.
429  template<typename _T1, typename _T2>
430  inline _GLIBCXX_CONSTEXPR bool
431  operator==(const pair<_T1, _T2>& __x, const pair<_T1, _T2>& __y)
432  { return __x.first == __y.first && __x.second == __y.second; }
433 
434  /// <http://gcc.gnu.org/onlinedocs/libstdc++/manual/utilities.html>
435  template<typename _T1, typename _T2>
436  inline _GLIBCXX_CONSTEXPR bool
437  operator<(const pair<_T1, _T2>& __x, const pair<_T1, _T2>& __y)
438  { return __x.first < __y.first
439  || (!(__y.first < __x.first) && __x.second < __y.second); }
440 
441  /// Uses @c operator== to find the result.
442  template<typename _T1, typename _T2>
443  inline _GLIBCXX_CONSTEXPR bool
444  operator!=(const pair<_T1, _T2>& __x, const pair<_T1, _T2>& __y)
445  { return !(__x == __y); }
446 
447  /// Uses @c operator< to find the result.
448  template<typename _T1, typename _T2>
449  inline _GLIBCXX_CONSTEXPR bool
450  operator>(const pair<_T1, _T2>& __x, const pair<_T1, _T2>& __y)
451  { return __y < __x; }
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 !(__y < __x); }
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 !(__x < __y); }
464 
465 #if __cplusplus >= 201103L
466  /// See std::pair::swap().
467  // Note: no std::swap overloads in C++03 mode, this has performance
468  // implications, see, eg, libstdc++/38466.
469  template<typename _T1, typename _T2>
470  inline void
471  swap(pair<_T1, _T2>& __x, pair<_T1, _T2>& __y)
472  noexcept(noexcept(__x.swap(__y)))
473  { __x.swap(__y); }
474 #endif
475 
476  /**
477  * @brief A convenience wrapper for creating a pair from two objects.
478  * @param __x The first object.
479  * @param __y The second object.
480  * @return A newly-constructed pair<> object of the appropriate type.
481  *
482  * The standard requires that the objects be passed by reference-to-const,
483  * but LWG issue #181 says they should be passed by const value. We follow
484  * the LWG by default.
485  */
486  // _GLIBCXX_RESOLVE_LIB_DEFECTS
487  // 181. make_pair() unintended behavior
488 #if __cplusplus >= 201103L
489  // NB: DR 706.
490  template<typename _T1, typename _T2>
491  constexpr pair<typename __decay_and_strip<_T1>::__type,
492  typename __decay_and_strip<_T2>::__type>
493  make_pair(_T1&& __x, _T2&& __y)
494  {
495  typedef typename __decay_and_strip<_T1>::__type __ds_type1;
496  typedef typename __decay_and_strip<_T2>::__type __ds_type2;
497  typedef pair<__ds_type1, __ds_type2> __pair_type;
498  return __pair_type(std::forward<_T1>(__x), std::forward<_T2>(__y));
499  }
500 #else
501  template<typename _T1, typename _T2>
502  inline pair<_T1, _T2>
503  make_pair(_T1 __x, _T2 __y)
504  { return pair<_T1, _T2>(__x, __y); }
505 #endif
506 
507  /// @}
508 
509 _GLIBCXX_END_NAMESPACE_VERSION
510 } // namespace std
511 
512 #endif /* _STL_PAIR_H */
std::pair::second
_T2 second
first is a copy of the first object
Definition: stl_pair.h:196
std::tuple
Primary class template, tuple.
Definition: tuple:461
std::pair::pair
constexpr pair()
second is a copy of the second object
Definition: stl_pair.h:210
std::pair::first
_T1 first
second_type is the second bound type
Definition: stl_pair.h:195
std::pair< _BiIter, _BiIter >::_PCCP
_PCC< true, _BiIter, _BiIter > _PCCP
Definition: stl_pair.h:233
std::piecewise_construct
constexpr piecewise_construct_t piecewise_construct
piecewise_construct
Definition: stl_pair.h:79
std::pair::second_type
_T2 second_type
first_type is the first bound type
Definition: stl_pair.h:193
std::pair
Struct holding two objects of arbitrary type.
Definition: stl_pair.h:190
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:493
std
ISO C++ entities toplevel namespace is std.
std::pair< _BiIter, _BiIter >::_PCCFP
_PCC<!is_same< _BiIter, _U1 >::value||!is_same< _BiIter, _U2 >::value, _BiIter, _BiIter > _PCCFP
Definition: stl_pair.h:264