libstdc++
stl_pair.h
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1 // Pair implementation -*- C++ -*-
2 
3 // Copyright (C) 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009,
4 // 2010, 2011, 2012
5 // Free Software Foundation, Inc.
6 //
7 // This file is part of the GNU ISO C++ Library. This library is free
8 // software; you can redistribute it and/or modify it under the
9 // terms of the GNU General Public License as published by the
10 // Free Software Foundation; either version 3, or (at your option)
11 // any later version.
12 
13 // This library is distributed in the hope that it will be useful,
14 // but WITHOUT ANY WARRANTY; without even the implied warranty of
15 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
16 // GNU General Public License for more details.
17 
18 // Under Section 7 of GPL version 3, you are granted additional
19 // permissions described in the GCC Runtime Library Exception, version
20 // 3.1, as published by the Free Software Foundation.
21 
22 // You should have received a copy of the GNU General Public License and
23 // a copy of the GCC Runtime Library Exception along with this program;
24 // see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
25 // <http://www.gnu.org/licenses/>.
26 
27 /*
28  *
29  * Copyright (c) 1994
30  * Hewlett-Packard Company
31  *
32  * Permission to use, copy, modify, distribute and sell this software
33  * and its documentation for any purpose is hereby granted without fee,
34  * provided that the above copyright notice appear in all copies and
35  * that both that copyright notice and this permission notice appear
36  * in supporting documentation. Hewlett-Packard Company makes no
37  * representations about the suitability of this software for any
38  * purpose. It is provided "as is" without express or implied warranty.
39  *
40  *
41  * Copyright (c) 1996,1997
42  * Silicon Graphics Computer Systems, Inc.
43  *
44  * Permission to use, copy, modify, distribute and sell this software
45  * and its documentation for any purpose is hereby granted without fee,
46  * provided that the above copyright notice appear in all copies and
47  * that both that copyright notice and this permission notice appear
48  * in supporting documentation. Silicon Graphics makes no
49  * representations about the suitability of this software for any
50  * purpose. It is provided "as is" without express or implied warranty.
51  */
52 
53 /** @file bits/stl_pair.h
54  * This is an internal header file, included by other library headers.
55  * Do not attempt to use it directly. @headername{utility}
56  */
57 
58 #ifndef _STL_PAIR_H
59 #define _STL_PAIR_H 1
60 
61 #include <bits/move.h> // for std::move / std::forward, and std::swap
62 
63 #ifdef __GXX_EXPERIMENTAL_CXX0X__
64 #include <type_traits> // for std::__decay_and_strip too
65 #endif
66 
67 namespace std _GLIBCXX_VISIBILITY(default)
68 {
69 _GLIBCXX_BEGIN_NAMESPACE_VERSION
70 
71 #ifdef __GXX_EXPERIMENTAL_CXX0X__
72  /// piecewise_construct_t
74 
75  /// piecewise_construct
77 
78  // Forward declarations.
79  template<typename...>
80  class tuple;
81 
82  template<std::size_t...>
83  struct _Index_tuple;
84 #endif
85 
86  /// Struct holding two objects of arbitrary type.
87  template<class _T1, class _T2>
88  struct pair
89  {
90  typedef _T1 first_type; /// @c first_type is the first bound type
91  typedef _T2 second_type; /// @c second_type is the second bound type
92 
93  _T1 first; /// @c first is a copy of the first object
94  _T2 second; /// @c second is a copy of the second object
95 
96  // _GLIBCXX_RESOLVE_LIB_DEFECTS
97  // 265. std::pair::pair() effects overly restrictive
98  /** The default constructor creates @c first and @c second using their
99  * respective default constructors. */
100  _GLIBCXX_CONSTEXPR pair()
101  : first(), second() { }
102 
103  /** Two objects may be passed to a @c pair constructor to be copied. */
104  _GLIBCXX_CONSTEXPR pair(const _T1& __a, const _T2& __b)
105  : first(__a), second(__b) { }
106 
107  /** There is also a templated copy ctor for the @c pair class itself. */
108 #ifndef __GXX_EXPERIMENTAL_CXX0X__
109  template<class _U1, class _U2>
110  pair(const pair<_U1, _U2>& __p)
111  : first(__p.first), second(__p.second) { }
112 #else
113  template<class _U1, class _U2, class = typename
114  enable_if<__and_<is_convertible<const _U1&, _T1>,
115  is_convertible<const _U2&, _T2>>::value>::type>
116  constexpr pair(const pair<_U1, _U2>& __p)
117  : first(__p.first), second(__p.second) { }
118 
119  constexpr pair(const pair&) = default;
120  constexpr pair(pair&&) = default;
121 
122  // DR 811.
123  template<class _U1, class = typename
125  constexpr pair(_U1&& __x, const _T2& __y)
126  : first(std::forward<_U1>(__x)), second(__y) { }
127 
128  template<class _U2, class = typename
129  enable_if<is_convertible<_U2, _T2>::value>::type>
130  constexpr pair(const _T1& __x, _U2&& __y)
131  : first(__x), second(std::forward<_U2>(__y)) { }
132 
133  template<class _U1, class _U2, class = typename
134  enable_if<__and_<is_convertible<_U1, _T1>,
135  is_convertible<_U2, _T2>>::value>::type>
136  constexpr pair(_U1&& __x, _U2&& __y)
137  : first(std::forward<_U1>(__x)), second(std::forward<_U2>(__y)) { }
138 
139  template<class _U1, class _U2, class = typename
140  enable_if<__and_<is_convertible<_U1, _T1>,
141  is_convertible<_U2, _T2>>::value>::type>
142  constexpr pair(pair<_U1, _U2>&& __p)
143  : first(std::forward<_U1>(__p.first)),
144  second(std::forward<_U2>(__p.second)) { }
145 
146  template<typename... _Args1, typename... _Args2>
147  pair(piecewise_construct_t, tuple<_Args1...>, tuple<_Args2...>);
148 
149  pair&
150  operator=(const pair& __p)
151  {
152  first = __p.first;
153  second = __p.second;
154  return *this;
155  }
156 
157  pair&
158  operator=(pair&& __p)
159  noexcept(__and_<is_nothrow_move_assignable<_T1>,
160  is_nothrow_move_assignable<_T2>>::value)
161  {
162  first = std::forward<first_type>(__p.first);
163  second = std::forward<second_type>(__p.second);
164  return *this;
165  }
166 
167  template<class _U1, class _U2>
168  pair&
169  operator=(const pair<_U1, _U2>& __p)
170  {
171  first = __p.first;
172  second = __p.second;
173  return *this;
174  }
175 
176  template<class _U1, class _U2>
177  pair&
178  operator=(pair<_U1, _U2>&& __p)
179  {
180  first = std::forward<_U1>(__p.first);
181  second = std::forward<_U2>(__p.second);
182  return *this;
183  }
184 
185  void
186  swap(pair& __p)
187  noexcept(noexcept(swap(first, __p.first))
188  && noexcept(swap(second, __p.second)))
189  {
190  using std::swap;
191  swap(first, __p.first);
192  swap(second, __p.second);
193  }
194 
195  private:
196  template<typename... _Args1, std::size_t... _Indexes1,
197  typename... _Args2, std::size_t... _Indexes2>
198  pair(tuple<_Args1...>&, tuple<_Args2...>&,
199  _Index_tuple<_Indexes1...>, _Index_tuple<_Indexes2...>);
200 #endif
201  };
202 
203  /// Two pairs of the same type are equal iff their members are equal.
204  template<class _T1, class _T2>
205  inline _GLIBCXX_CONSTEXPR bool
206  operator==(const pair<_T1, _T2>& __x, const pair<_T1, _T2>& __y)
207  { return __x.first == __y.first && __x.second == __y.second; }
208 
209  /// <http://gcc.gnu.org/onlinedocs/libstdc++/manual/utilities.html>
210  template<class _T1, class _T2>
211  inline _GLIBCXX_CONSTEXPR bool
212  operator<(const pair<_T1, _T2>& __x, const pair<_T1, _T2>& __y)
213  { return __x.first < __y.first
214  || (!(__y.first < __x.first) && __x.second < __y.second); }
215 
216  /// Uses @c operator== to find the result.
217  template<class _T1, class _T2>
218  inline _GLIBCXX_CONSTEXPR bool
219  operator!=(const pair<_T1, _T2>& __x, const pair<_T1, _T2>& __y)
220  { return !(__x == __y); }
221 
222  /// Uses @c operator< to find the result.
223  template<class _T1, class _T2>
224  inline _GLIBCXX_CONSTEXPR bool
225  operator>(const pair<_T1, _T2>& __x, const pair<_T1, _T2>& __y)
226  { return __y < __x; }
227 
228  /// Uses @c operator< to find the result.
229  template<class _T1, class _T2>
230  inline _GLIBCXX_CONSTEXPR bool
231  operator<=(const pair<_T1, _T2>& __x, const pair<_T1, _T2>& __y)
232  { return !(__y < __x); }
233 
234  /// Uses @c operator< to find the result.
235  template<class _T1, class _T2>
236  inline _GLIBCXX_CONSTEXPR bool
237  operator>=(const pair<_T1, _T2>& __x, const pair<_T1, _T2>& __y)
238  { return !(__x < __y); }
239 
240 #ifdef __GXX_EXPERIMENTAL_CXX0X__
241  /// See std::pair::swap().
242  // Note: no std::swap overloads in C++03 mode, this has performance
243  // implications, see, eg, libstdc++/38466.
244  template<class _T1, class _T2>
245  inline void
247  noexcept(noexcept(__x.swap(__y)))
248  { __x.swap(__y); }
249 #endif
250 
251  /**
252  * @brief A convenience wrapper for creating a pair from two objects.
253  * @param __x The first object.
254  * @param __y The second object.
255  * @return A newly-constructed pair<> object of the appropriate type.
256  *
257  * The standard requires that the objects be passed by reference-to-const,
258  * but LWG issue #181 says they should be passed by const value. We follow
259  * the LWG by default.
260  */
261  // _GLIBCXX_RESOLVE_LIB_DEFECTS
262  // 181. make_pair() unintended behavior
263 #ifdef __GXX_EXPERIMENTAL_CXX0X__
264  // NB: DR 706.
265  template<class _T1, class _T2>
266  constexpr pair<typename __decay_and_strip<_T1>::__type,
267  typename __decay_and_strip<_T2>::__type>
268  make_pair(_T1&& __x, _T2&& __y)
269  {
270  typedef typename __decay_and_strip<_T1>::__type __ds_type1;
271  typedef typename __decay_and_strip<_T2>::__type __ds_type2;
272  typedef pair<__ds_type1, __ds_type2> __pair_type;
273  return __pair_type(std::forward<_T1>(__x), std::forward<_T2>(__y));
274  }
275 #else
276  template<class _T1, class _T2>
277  inline pair<_T1, _T2>
278  make_pair(_T1 __x, _T2 __y)
279  { return pair<_T1, _T2>(__x, __y); }
280 #endif
281 
282 _GLIBCXX_END_NAMESPACE_VERSION
283 } // namespace
284 
285 #endif /* _STL_PAIR_H */