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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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  template <typename _T1, typename _T2, typename _U1, typename _U2>
91  constexpr bool _ConstructiblePair()
92  {
93  return __and_<is_constructible<_T1, const _U1&>,
94  is_constructible<_T2, const _U2&>>::value;
95  }
96 
97  template <typename _T1, typename _T2, typename _U1, typename _U2>
98  constexpr bool _ImplicitlyConvertiblePair()
99  {
100  return __and_<is_convertible<const _U1&, _T1>,
101  is_convertible<const _U2&, _T2>>::value;
102  }
103 
104  template <typename _T1, typename _T2, typename _U1, typename _U2>
105  constexpr bool _MoveConstructiblePair()
106  {
107  return __and_<is_constructible<_T1, _U1&&>,
108  is_constructible<_T2, _U2&&>>::value;
109  }
110 
111  template <typename _T1, typename _T2, typename _U1, typename _U2>
112  constexpr bool _ImplicitlyMoveConvertiblePair()
113  {
114  return __and_<is_convertible<_U1&&, _T1>,
115  is_convertible<_U2&&, _T2>>::value;
116  }
117 
118 
119 #endif
120 
121  /**
122  * @brief Struct holding two objects of arbitrary type.
123  *
124  * @tparam _T1 Type of first object.
125  * @tparam _T2 Type of second object.
126  */
127  template<typename _T1, typename _T2>
128  struct pair
129  {
130  typedef _T1 first_type; /// @c first_type is the first bound type
131  typedef _T2 second_type; /// @c second_type is the second bound type
132 
133  _T1 first; /// @c first is a copy of the first object
134  _T2 second; /// @c second is a copy of the second object
135 
136  // _GLIBCXX_RESOLVE_LIB_DEFECTS
137  // 265. std::pair::pair() effects overly restrictive
138  /** The default constructor creates @c first and @c second using their
139  * respective default constructors. */
140 #if __cplusplus >= 201103L
141  template <typename _U1 = _T1,
142  typename _U2 = _T2,
143  typename enable_if<__and_<
144  __is_implicitly_default_constructible<_U1>,
145  __is_implicitly_default_constructible<_U2>>
146  ::value, bool>::type = true>
147 #endif
148  _GLIBCXX_CONSTEXPR pair()
149  : first(), second() { }
150 
151 #if __cplusplus >= 201103L
152  template <typename _U1 = _T1,
153  typename _U2 = _T2,
154  typename enable_if<__and_<
155  is_default_constructible<_U1>,
156  is_default_constructible<_U2>,
157  __not_<
158  __and_<__is_implicitly_default_constructible<_U1>,
159  __is_implicitly_default_constructible<_U2>>>>
160  ::value, bool>::type = false>
161  explicit constexpr pair()
162  : first(), second() { }
163 #endif
164 
165  /** Two objects may be passed to a @c pair constructor to be copied. */
166 #if __cplusplus < 201103L
167  pair(const _T1& __a, const _T2& __b)
168  : first(__a), second(__b) { }
169 #else
170  template<typename _U1 = _T1, typename _U2=_T2, typename
171  enable_if<_ConstructiblePair<_T1, _T2, _U1, _U2>()
172  && _ImplicitlyConvertiblePair<_T1, _T2, _U1, _U2>(),
173  bool>::type=true>
174  constexpr pair(const _T1& __a, const _T2& __b)
175  : first(__a), second(__b) { }
176 
177  template<typename _U1 = _T1, typename _U2=_T2, typename
178  enable_if<_ConstructiblePair<_T1, _T2, _U1, _U2>()
179  && !_ImplicitlyConvertiblePair<_T1, _T2, _U1, _U2>(),
180  bool>::type=false>
181  explicit constexpr pair(const _T1& __a, const _T2& __b)
182  : first(__a), second(__b) { }
183 #endif
184 
185  /** There is also a templated copy ctor for the @c pair class itself. */
186 #if __cplusplus < 201103L
187  template<typename _U1, typename _U2>
188  pair(const pair<_U1, _U2>& __p)
189  : first(__p.first), second(__p.second) { }
190 #else
191  template<typename _U1, typename _U2, typename
192  enable_if<_ConstructiblePair<_T1, _T2, _U1, _U2>()
193  && _ImplicitlyConvertiblePair<_T1, _T2, _U1, _U2>(),
194  bool>::type=true>
195  constexpr pair(const pair<_U1, _U2>& __p)
196  : first(__p.first), second(__p.second) { }
197 
198  template<typename _U1, typename _U2, typename
199  enable_if<_ConstructiblePair<_T1, _T2, _U1, _U2>()
200  && !_ImplicitlyConvertiblePair<_T1, _T2, _U1, _U2>(),
201  bool>::type=false>
202  explicit constexpr pair(const pair<_U1, _U2>& __p)
203  : first(__p.first), second(__p.second) { }
204 
205  constexpr pair(const pair&) = default;
206  constexpr pair(pair&&) = default;
207 
208  // DR 811.
209  template<typename _U1, typename
210  enable_if<_ConstructiblePair<_T2, _T2, _T2, _T2>()
211  && _MoveConstructiblePair<_T1, _T2, _U1, _T2>()
212  && _ImplicitlyConvertiblePair<_T2, _T2, _T2, _T2>()
213  && _ImplicitlyMoveConvertiblePair<_T1, _T2,
214  _U1, _T2>(),
215  bool>::type=true>
216  constexpr pair(_U1&& __x, const _T2& __y)
217  : first(std::forward<_U1>(__x)), second(__y) { }
218 
219  template<typename _U1, typename
220  enable_if<_ConstructiblePair<_T2, _T2, _T2, _T2>()
221  && _MoveConstructiblePair<_T1, _T2, _U1, _T2>()
222  && (!_ImplicitlyConvertiblePair<_T2, _T2, _T2, _T2>()
223  || !_ImplicitlyMoveConvertiblePair<_T1, _T2,
224  _U1, _T2>()),
225  bool>::type=false>
226  explicit constexpr pair(_U1&& __x, const _T2& __y)
227  : first(std::forward<_U1>(__x)), second(__y) { }
228 
229  template<typename _U2, typename
230  enable_if<_ConstructiblePair<_T1, _T1, _T1, _T1>()
231  && _MoveConstructiblePair<_T1, _T2, _T1, _U2>()
232  && _ImplicitlyConvertiblePair<_T1, _T1, _T1, _T1>()
233  && _ImplicitlyMoveConvertiblePair<_T1, _T2,
234  _T1, _U2>(),
235  bool>::type=true>
236  constexpr pair(const _T1& __x, _U2&& __y)
237  : first(__x), second(std::forward<_U2>(__y)) { }
238 
239  template<typename _U2, typename
240  enable_if<_ConstructiblePair<_T1, _T1, _T1, _T1>()
241  && _MoveConstructiblePair<_T1, _T2, _T1, _U2>()
242  && (!_ImplicitlyConvertiblePair<_T1, _T1, _T1, _T1>()
243  || !_ImplicitlyMoveConvertiblePair<_T1, _T2,
244  _T1, _U2>()),
245  bool>::type=false>
246  explicit pair(const _T1& __x, _U2&& __y)
247  : first(__x), second(std::forward<_U2>(__y)) { }
248 
249  template<typename _U1, typename _U2, typename
250  enable_if<_MoveConstructiblePair<_T1, _T2, _U1, _U2>()
251  && _ImplicitlyMoveConvertiblePair<_T1, _T2,
252  _U1, _U2>(),
253  bool>::type=true>
254  constexpr pair(_U1&& __x, _U2&& __y)
255  : first(std::forward<_U1>(__x)), second(std::forward<_U2>(__y)) { }
256 
257  template<typename _U1, typename _U2, typename
258  enable_if<_MoveConstructiblePair<_T1, _T2, _U1, _U2>()
259  && !_ImplicitlyMoveConvertiblePair<_T1, _T2,
260  _U1, _U2>(),
261  bool>::type=false>
262  explicit constexpr pair(_U1&& __x, _U2&& __y)
263  : first(std::forward<_U1>(__x)), second(std::forward<_U2>(__y)) { }
264 
265 
266  template<typename _U1, typename _U2, typename
267  enable_if<_MoveConstructiblePair<_T1, _T2, _U1, _U2>()
268  && _ImplicitlyMoveConvertiblePair<_T1, _T2,
269  _U1, _U2>(),
270  bool>::type=true>
271  constexpr pair(pair<_U1, _U2>&& __p)
272  : first(std::forward<_U1>(__p.first)),
273  second(std::forward<_U2>(__p.second)) { }
274 
275  template<typename _U1, typename _U2, typename
276  enable_if<_MoveConstructiblePair<_T1, _T2, _U1, _U2>()
277  && !_ImplicitlyMoveConvertiblePair<_T1, _T2,
278  _U1, _U2>(),
279  bool>::type=false>
280  explicit constexpr pair(pair<_U1, _U2>&& __p)
281  : first(std::forward<_U1>(__p.first)),
282  second(std::forward<_U2>(__p.second)) { }
283 
284  template<typename... _Args1, typename... _Args2>
286 
287  pair&
288  operator=(const pair& __p)
289  {
290  first = __p.first;
291  second = __p.second;
292  return *this;
293  }
294 
295  pair&
296  operator=(pair&& __p)
297  noexcept(__and_<is_nothrow_move_assignable<_T1>,
298  is_nothrow_move_assignable<_T2>>::value)
299  {
300  first = std::forward<first_type>(__p.first);
301  second = std::forward<second_type>(__p.second);
302  return *this;
303  }
304 
305  template<typename _U1, typename _U2>
306  pair&
307  operator=(const pair<_U1, _U2>& __p)
308  {
309  first = __p.first;
310  second = __p.second;
311  return *this;
312  }
313 
314  template<typename _U1, typename _U2>
315  pair&
316  operator=(pair<_U1, _U2>&& __p)
317  {
318  first = std::forward<_U1>(__p.first);
319  second = std::forward<_U2>(__p.second);
320  return *this;
321  }
322 
323  void
324  swap(pair& __p)
325  noexcept(__is_nothrow_swappable<_T1>::value
326  && __is_nothrow_swappable<_T2>::value)
327  {
328  using std::swap;
329  swap(first, __p.first);
330  swap(second, __p.second);
331  }
332 
333  private:
334  template<typename... _Args1, std::size_t... _Indexes1,
335  typename... _Args2, std::size_t... _Indexes2>
337  _Index_tuple<_Indexes1...>, _Index_tuple<_Indexes2...>);
338 #endif
339  };
340 
341  /// Two pairs of the same type are equal iff their members are equal.
342  template<typename _T1, typename _T2>
343  inline _GLIBCXX_CONSTEXPR bool
344  operator==(const pair<_T1, _T2>& __x, const pair<_T1, _T2>& __y)
345  { return __x.first == __y.first && __x.second == __y.second; }
346 
347  /// <http://gcc.gnu.org/onlinedocs/libstdc++/manual/utilities.html>
348  template<typename _T1, typename _T2>
349  inline _GLIBCXX_CONSTEXPR bool
350  operator<(const pair<_T1, _T2>& __x, const pair<_T1, _T2>& __y)
351  { return __x.first < __y.first
352  || (!(__y.first < __x.first) && __x.second < __y.second); }
353 
354  /// Uses @c operator== to find the result.
355  template<typename _T1, typename _T2>
356  inline _GLIBCXX_CONSTEXPR bool
357  operator!=(const pair<_T1, _T2>& __x, const pair<_T1, _T2>& __y)
358  { return !(__x == __y); }
359 
360  /// Uses @c operator< to find the result.
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 __y < __x; }
365 
366  /// Uses @c operator< to find the result.
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 !(__y < __x); }
371 
372  /// Uses @c operator< to find the result.
373  template<typename _T1, typename _T2>
374  inline _GLIBCXX_CONSTEXPR bool
375  operator>=(const pair<_T1, _T2>& __x, const pair<_T1, _T2>& __y)
376  { return !(__x < __y); }
377 
378 #if __cplusplus >= 201103L
379  /// See std::pair::swap().
380  // Note: no std::swap overloads in C++03 mode, this has performance
381  // implications, see, eg, libstdc++/38466.
382  template<typename _T1, typename _T2>
383  inline void
385  noexcept(noexcept(__x.swap(__y)))
386  { __x.swap(__y); }
387 #endif
388 
389  /**
390  * @brief A convenience wrapper for creating a pair from two objects.
391  * @param __x The first object.
392  * @param __y The second object.
393  * @return A newly-constructed pair<> object of the appropriate type.
394  *
395  * The standard requires that the objects be passed by reference-to-const,
396  * but LWG issue #181 says they should be passed by const value. We follow
397  * the LWG by default.
398  */
399  // _GLIBCXX_RESOLVE_LIB_DEFECTS
400  // 181. make_pair() unintended behavior
401 #if __cplusplus >= 201103L
402  // NB: DR 706.
403  template<typename _T1, typename _T2>
405  typename __decay_and_strip<_T2>::__type>
406  make_pair(_T1&& __x, _T2&& __y)
407  {
408  typedef typename __decay_and_strip<_T1>::__type __ds_type1;
409  typedef typename __decay_and_strip<_T2>::__type __ds_type2;
410  typedef pair<__ds_type1, __ds_type2> __pair_type;
411  return __pair_type(std::forward<_T1>(__x), std::forward<_T2>(__y));
412  }
413 #else
414  template<typename _T1, typename _T2>
415  inline pair<_T1, _T2>
416  make_pair(_T1 __x, _T2 __y)
417  { return pair<_T1, _T2>(__x, __y); }
418 #endif
419 
420  /// @}
421 
422 _GLIBCXX_END_NAMESPACE_VERSION
423 } // namespace std
424 
425 #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:148
constexpr pair(const pair< _U1, _U2 > &__p)
Definition: stl_pair.h:195
constexpr pair(const _T1 &__a, const _T2 &__b)
Definition: stl_pair.h:174
constexpr piecewise_construct_t piecewise_construct
piecewise_construct
Definition: stl_pair.h:79
ISO C++ entities toplevel namespace is std.
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:406
Primary class template, tuple.
Definition: tuple:461
_T2 second
first is a copy of the first object
Definition: stl_pair.h:134
Struct holding two objects of arbitrary type.
Definition: stl_pair.h:128
_T1 first
second_type is the second bound type
Definition: stl_pair.h:133
_T2 second_type
first_type is the first bound type
Definition: stl_pair.h:131