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
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,
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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
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 decayed types are the same to
92  // avoid querying those properties for incomplete types.
93  template <typename _T1, typename _T2, typename _U1, typename _U2>
94  constexpr bool _ConstructiblePair()
95  {
96  return __and_<__or_<is_same<typename decay<_T1>::type,
97  typename decay<_U1>::type>,
98  is_constructible<_T1, const _U1&>>,
99  __or_<is_same<typename decay<_T2>::type,
100  typename decay<_U2>::type>,
101  is_constructible<_T2, const _U2&>>>::value;
102  }
103 
104  template <typename _T1, typename _T2, typename _U1, typename _U2>
105  constexpr bool _ImplicitlyConvertiblePair()
106  {
107  return __and_<__or_<is_same<typename decay<_T1>::type,
108  typename decay<_U1>::type>,
109  is_convertible<const _U1&, _T1>>,
110  __or_<is_same<typename decay<_T2>::type,
111  typename decay<_U2>::type>,
112  is_convertible<const _U2&, _T2>>>::value;
113  }
114 
115  template <typename _T1, typename _T2, typename _U1, typename _U2>
116  constexpr bool _MoveConstructiblePair()
117  {
118  return __and_<__or_<is_same<typename decay<_T1>::type,
119  typename decay<_U1>::type>,
120  is_constructible<_T1, _U1&&>>,
121  __or_<is_same<typename decay<_T2>::type,
122  typename decay<_U2>::type>,
123  is_constructible<_T2, _U2&&>>>::value;
124  }
125 
126  template <typename _T1, typename _T2, typename _U1, typename _U2>
127  constexpr bool _ImplicitlyMoveConvertiblePair()
128  {
129  return __and_<__or_<is_same<typename decay<_T1>::type,
130  typename decay<_U1>::type>,
131  is_convertible<_U1&&, _T1>>,
132  __or_<is_same<typename decay<_T2>::type,
133  typename decay<_U2>::type>,
134  is_convertible<_U2&&, _T2>>>::value;
135  }
136 
137 
138 #endif
139 
140  /**
141  * @brief Struct holding two objects of arbitrary type.
142  *
143  * @tparam _T1 Type of first object.
144  * @tparam _T2 Type of second object.
145  */
146  template<typename _T1, typename _T2>
147  struct pair
148  {
149  typedef _T1 first_type; /// @c first_type is the first bound type
150  typedef _T2 second_type; /// @c second_type is the second bound type
151 
152  _T1 first; /// @c first is a copy of the first object
153  _T2 second; /// @c second is a copy of the second object
154 
155  // _GLIBCXX_RESOLVE_LIB_DEFECTS
156  // 265. std::pair::pair() effects overly restrictive
157  /** The default constructor creates @c first and @c second using their
158  * respective default constructors. */
159 #if __cplusplus >= 201103L
160  template <typename _U1 = _T1,
161  typename _U2 = _T2,
162  typename enable_if<__and_<
163  __is_implicitly_default_constructible<_U1>,
164  __is_implicitly_default_constructible<_U2>>
165  ::value, bool>::type = true>
166 #endif
167  _GLIBCXX_CONSTEXPR pair()
168  : first(), second() { }
169 
170 #if __cplusplus >= 201103L
171  template <typename _U1 = _T1,
172  typename _U2 = _T2,
173  typename enable_if<__and_<
174  is_default_constructible<_U1>,
175  is_default_constructible<_U2>,
176  __not_<
177  __and_<__is_implicitly_default_constructible<_U1>,
178  __is_implicitly_default_constructible<_U2>>>>
179  ::value, bool>::type = false>
180  explicit constexpr pair()
181  : first(), second() { }
182 #endif
183 
184  /** Two objects may be passed to a @c pair constructor to be copied. */
185 #if __cplusplus < 201103L
186  pair(const _T1& __a, const _T2& __b)
187  : first(__a), second(__b) { }
188 #else
189  template<typename _U1 = _T1, typename _U2=_T2, typename
190  enable_if<_ConstructiblePair<_T1, _T2, _U1, _U2>()
191  && _ImplicitlyConvertiblePair<_T1, _T2, _U1, _U2>(),
192  bool>::type=true>
193  constexpr pair(const _T1& __a, const _T2& __b)
194  : first(__a), second(__b) { }
195 
196  template<typename _U1 = _T1, typename _U2=_T2, typename
197  enable_if<_ConstructiblePair<_T1, _T2, _U1, _U2>()
198  && !_ImplicitlyConvertiblePair<_T1, _T2, _U1, _U2>(),
199  bool>::type=false>
200  explicit constexpr pair(const _T1& __a, const _T2& __b)
201  : first(__a), second(__b) { }
202 #endif
203 
204  /** There is also a templated copy ctor for the @c pair class itself. */
205 #if __cplusplus < 201103L
206  template<typename _U1, typename _U2>
207  pair(const pair<_U1, _U2>& __p)
208  : first(__p.first), second(__p.second) { }
209 #else
210  template<typename _U1, typename _U2, typename
211  enable_if<_ConstructiblePair<_T1, _T2, _U1, _U2>()
212  && _ImplicitlyConvertiblePair<_T1, _T2, _U1, _U2>(),
213  bool>::type=true>
214  constexpr pair(const pair<_U1, _U2>& __p)
215  : first(__p.first), second(__p.second) { }
216 
217  template<typename _U1, typename _U2, typename
218  enable_if<_ConstructiblePair<_T1, _T2, _U1, _U2>()
219  && !_ImplicitlyConvertiblePair<_T1, _T2, _U1, _U2>(),
220  bool>::type=false>
221  explicit constexpr pair(const pair<_U1, _U2>& __p)
222  : first(__p.first), second(__p.second) { }
223 
224  constexpr pair(const pair&) = default;
225  constexpr pair(pair&&) = default;
226 
227  // DR 811.
228  template<typename _U1, typename
229  enable_if<_ConstructiblePair<_T2, _T2, _T2, _T2>()
230  && _MoveConstructiblePair<_T1, _T2, _U1, _T2>()
231  && _ImplicitlyConvertiblePair<_T2, _T2, _T2, _T2>()
232  && _ImplicitlyMoveConvertiblePair<_T1, _T2,
233  _U1, _T2>(),
234  bool>::type=true>
235  constexpr pair(_U1&& __x, const _T2& __y)
236  : first(std::forward<_U1>(__x)), second(__y) { }
237 
238  template<typename _U1, typename
239  enable_if<_ConstructiblePair<_T2, _T2, _T2, _T2>()
240  && _MoveConstructiblePair<_T1, _T2, _U1, _T2>()
241  && (!_ImplicitlyConvertiblePair<_T2, _T2, _T2, _T2>()
242  || !_ImplicitlyMoveConvertiblePair<_T1, _T2,
243  _U1, _T2>()),
244  bool>::type=false>
245  explicit constexpr pair(_U1&& __x, const _T2& __y)
246  : first(std::forward<_U1>(__x)), second(__y) { }
247 
248  template<typename _U2, typename
249  enable_if<_ConstructiblePair<_T1, _T1, _T1, _T1>()
250  && _MoveConstructiblePair<_T1, _T2, _T1, _U2>()
251  && _ImplicitlyConvertiblePair<_T1, _T1, _T1, _T1>()
252  && _ImplicitlyMoveConvertiblePair<_T1, _T2,
253  _T1, _U2>(),
254  bool>::type=true>
255  constexpr pair(const _T1& __x, _U2&& __y)
256  : first(__x), second(std::forward<_U2>(__y)) { }
257 
258  template<typename _U2, typename
259  enable_if<_ConstructiblePair<_T1, _T1, _T1, _T1>()
260  && _MoveConstructiblePair<_T1, _T2, _T1, _U2>()
261  && (!_ImplicitlyConvertiblePair<_T1, _T1, _T1, _T1>()
262  || !_ImplicitlyMoveConvertiblePair<_T1, _T2,
263  _T1, _U2>()),
264  bool>::type=false>
265  explicit pair(const _T1& __x, _U2&& __y)
266  : first(__x), second(std::forward<_U2>(__y)) { }
267 
268  template<typename _U1, typename _U2, typename
269  enable_if<_MoveConstructiblePair<_T1, _T2, _U1, _U2>()
270  && _ImplicitlyMoveConvertiblePair<_T1, _T2,
271  _U1, _U2>(),
272  bool>::type=true>
273  constexpr pair(_U1&& __x, _U2&& __y)
274  : first(std::forward<_U1>(__x)), second(std::forward<_U2>(__y)) { }
275 
276  template<typename _U1, typename _U2, typename
277  enable_if<_MoveConstructiblePair<_T1, _T2, _U1, _U2>()
278  && !_ImplicitlyMoveConvertiblePair<_T1, _T2,
279  _U1, _U2>(),
280  bool>::type=false>
281  explicit constexpr pair(_U1&& __x, _U2&& __y)
282  : first(std::forward<_U1>(__x)), second(std::forward<_U2>(__y)) { }
283 
284 
285  template<typename _U1, typename _U2, typename
286  enable_if<_MoveConstructiblePair<_T1, _T2, _U1, _U2>()
287  && _ImplicitlyMoveConvertiblePair<_T1, _T2,
288  _U1, _U2>(),
289  bool>::type=true>
290  constexpr pair(pair<_U1, _U2>&& __p)
291  : first(std::forward<_U1>(__p.first)),
292  second(std::forward<_U2>(__p.second)) { }
293 
294  template<typename _U1, typename _U2, typename
295  enable_if<_MoveConstructiblePair<_T1, _T2, _U1, _U2>()
296  && !_ImplicitlyMoveConvertiblePair<_T1, _T2,
297  _U1, _U2>(),
298  bool>::type=false>
299  explicit constexpr pair(pair<_U1, _U2>&& __p)
300  : first(std::forward<_U1>(__p.first)),
301  second(std::forward<_U2>(__p.second)) { }
302 
303  template<typename... _Args1, typename... _Args2>
305 
306  pair&
307  operator=(const pair& __p)
308  {
309  first = __p.first;
310  second = __p.second;
311  return *this;
312  }
313 
314  pair&
315  operator=(pair&& __p)
316  noexcept(__and_<is_nothrow_move_assignable<_T1>,
317  is_nothrow_move_assignable<_T2>>::value)
318  {
319  first = std::forward<first_type>(__p.first);
320  second = std::forward<second_type>(__p.second);
321  return *this;
322  }
323 
324  template<typename _U1, typename _U2>
325  pair&
326  operator=(const pair<_U1, _U2>& __p)
327  {
328  first = __p.first;
329  second = __p.second;
330  return *this;
331  }
332 
333  template<typename _U1, typename _U2>
334  pair&
335  operator=(pair<_U1, _U2>&& __p)
336  {
337  first = std::forward<_U1>(__p.first);
338  second = std::forward<_U2>(__p.second);
339  return *this;
340  }
341 
342  void
343  swap(pair& __p)
344  noexcept(__is_nothrow_swappable<_T1>::value
345  && __is_nothrow_swappable<_T2>::value)
346  {
347  using std::swap;
348  swap(first, __p.first);
349  swap(second, __p.second);
350  }
351 
352  private:
353  template<typename... _Args1, std::size_t... _Indexes1,
354  typename... _Args2, std::size_t... _Indexes2>
356  _Index_tuple<_Indexes1...>, _Index_tuple<_Indexes2...>);
357 #endif
358  };
359 
360  /// Two pairs of the same type are equal iff their members are equal.
361  template<typename _T1, typename _T2>
362  inline _GLIBCXX_CONSTEXPR bool
363  operator==(const pair<_T1, _T2>& __x, const pair<_T1, _T2>& __y)
364  { return __x.first == __y.first && __x.second == __y.second; }
365 
366  /// <http://gcc.gnu.org/onlinedocs/libstdc++/manual/utilities.html>
367  template<typename _T1, typename _T2>
368  inline _GLIBCXX_CONSTEXPR bool
369  operator<(const pair<_T1, _T2>& __x, const pair<_T1, _T2>& __y)
370  { return __x.first < __y.first
371  || (!(__y.first < __x.first) && __x.second < __y.second); }
372 
373  /// Uses @c operator== to find the result.
374  template<typename _T1, typename _T2>
375  inline _GLIBCXX_CONSTEXPR bool
376  operator!=(const pair<_T1, _T2>& __x, const pair<_T1, _T2>& __y)
377  { return !(__x == __y); }
378 
379  /// Uses @c operator< to find the result.
380  template<typename _T1, typename _T2>
381  inline _GLIBCXX_CONSTEXPR bool
382  operator>(const pair<_T1, _T2>& __x, const pair<_T1, _T2>& __y)
383  { return __y < __x; }
384 
385  /// Uses @c operator< to find the result.
386  template<typename _T1, typename _T2>
387  inline _GLIBCXX_CONSTEXPR bool
388  operator<=(const pair<_T1, _T2>& __x, const pair<_T1, _T2>& __y)
389  { return !(__y < __x); }
390 
391  /// Uses @c operator< to find the result.
392  template<typename _T1, typename _T2>
393  inline _GLIBCXX_CONSTEXPR bool
394  operator>=(const pair<_T1, _T2>& __x, const pair<_T1, _T2>& __y)
395  { return !(__x < __y); }
396 
397 #if __cplusplus >= 201103L
398  /// See std::pair::swap().
399  // Note: no std::swap overloads in C++03 mode, this has performance
400  // implications, see, eg, libstdc++/38466.
401  template<typename _T1, typename _T2>
402  inline void
404  noexcept(noexcept(__x.swap(__y)))
405  { __x.swap(__y); }
406 #endif
407 
408  /**
409  * @brief A convenience wrapper for creating a pair from two objects.
410  * @param __x The first object.
411  * @param __y The second object.
412  * @return A newly-constructed pair<> object of the appropriate type.
413  *
414  * The standard requires that the objects be passed by reference-to-const,
415  * but LWG issue #181 says they should be passed by const value. We follow
416  * the LWG by default.
417  */
418  // _GLIBCXX_RESOLVE_LIB_DEFECTS
419  // 181. make_pair() unintended behavior
420 #if __cplusplus >= 201103L
421  // NB: DR 706.
422  template<typename _T1, typename _T2>
424  typename __decay_and_strip<_T2>::__type>
425  make_pair(_T1&& __x, _T2&& __y)
426  {
427  typedef typename __decay_and_strip<_T1>::__type __ds_type1;
428  typedef typename __decay_and_strip<_T2>::__type __ds_type2;
429  typedef pair<__ds_type1, __ds_type2> __pair_type;
430  return __pair_type(std::forward<_T1>(__x), std::forward<_T2>(__y));
431  }
432 #else
433  template<typename _T1, typename _T2>
434  inline pair<_T1, _T2>
435  make_pair(_T1 __x, _T2 __y)
436  { return pair<_T1, _T2>(__x, __y); }
437 #endif
438 
439  /// @}
440 
441 _GLIBCXX_END_NAMESPACE_VERSION
442 } // namespace std
443 
444 #endif /* _STL_PAIR_H */
piecewise_construct_t
Definition: stl_pair.h:76
constexpr pair()
second is a copy of the second object
Definition: stl_pair.h:167
_T1 first
second_type is the second bound type
Definition: stl_pair.h:152
Primary class template, tuple.
Definition: tuple:461
Struct holding two objects of arbitrary type.
Definition: stl_pair.h:147
_T2 second
first is a copy of the first object
Definition: stl_pair.h:153
constexpr piecewise_construct_t piecewise_construct
piecewise_construct
Definition: stl_pair.h:79
constexpr pair(const pair< _U1, _U2 > &__p)
Definition: stl_pair.h:214
ISO C++ entities toplevel namespace is std.
constexpr pair(const _T1 &__a, const _T2 &__b)
Definition: stl_pair.h:193
_T2 second_type
first_type is the first bound type
Definition: stl_pair.h:150
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:425