libstdc++
stl_pair.h
Go to the documentation of this file.
1 // Pair implementation -*- C++ -*-
2 
3 // Copyright (C) 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009
4 // Free Software Foundation, Inc.
5 //
6 // This file is part of the GNU ISO C++ Library. This library is free
7 // software; you can redistribute it and/or modify it under the
8 // terms of the GNU General Public License as published by the
9 // Free Software Foundation; either version 3, or (at your option)
10 // any later version.
11 
12 // This library is distributed in the hope that it will be useful,
13 // but WITHOUT ANY WARRANTY; without even the implied warranty of
14 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 // GNU General Public License for more details.
16 
17 // Under Section 7 of GPL version 3, you are granted additional
18 // permissions described in the GCC Runtime Library Exception, version
19 // 3.1, as published by the Free Software Foundation.
20 
21 // You should have received a copy of the GNU General Public License and
22 // a copy of the GCC Runtime Library Exception along with this program;
23 // see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
24 // <http://www.gnu.org/licenses/>.
25 
26 /*
27  *
28  * Copyright (c) 1994
29  * Hewlett-Packard Company
30  *
31  * Permission to use, copy, modify, distribute and sell this software
32  * and its documentation for any purpose is hereby granted without fee,
33  * provided that the above copyright notice appear in all copies and
34  * that both that copyright notice and this permission notice appear
35  * in supporting documentation. Hewlett-Packard Company makes no
36  * representations about the suitability of this software for any
37  * purpose. It is provided "as is" without express or implied warranty.
38  *
39  *
40  * Copyright (c) 1996,1997
41  * Silicon Graphics Computer Systems, Inc.
42  *
43  * Permission to use, copy, modify, distribute and sell this software
44  * and its documentation for any purpose is hereby granted without fee,
45  * provided that the above copyright notice appear in all copies and
46  * that both that copyright notice and this permission notice appear
47  * in supporting documentation. Silicon Graphics makes no
48  * representations about the suitability of this software for any
49  * purpose. It is provided "as is" without express or implied warranty.
50  */
51 
52 /** @file stl_pair.h
53  * This is an internal header file, included by other library headers.
54  * You should not attempt to use it directly.
55  */
56 
57 #ifndef _STL_PAIR_H
58 #define _STL_PAIR_H 1
59 
60 #include <bits/move.h> // for std::move / std::forward, std::decay, and
61  // std::swap
62 
63 _GLIBCXX_BEGIN_NAMESPACE(std)
64 
65  /// pair holds two objects of arbitrary type.
66  template<class _T1, class _T2>
67  struct pair
68  {
69  typedef _T1 first_type; ///< @c first_type is the first bound type
70  typedef _T2 second_type; ///< @c second_type is the second bound type
71 
72  _T1 first; ///< @c first is a copy of the first object
73  _T2 second; ///< @c second is a copy of the second object
74 
75  // _GLIBCXX_RESOLVE_LIB_DEFECTS
76  // 265. std::pair::pair() effects overly restrictive
77  /** The default constructor creates @c first and @c second using their
78  * respective default constructors. */
79  pair()
80  : first(), second() { }
81 
82  /** Two objects may be passed to a @c pair constructor to be copied. */
83  pair(const _T1& __a, const _T2& __b)
84  : first(__a), second(__b) { }
85 
86 #ifdef __GXX_EXPERIMENTAL_CXX0X__
87  template<class _U1, class _U2>
88  pair(_U1&& __x, _U2&& __y)
89  : first(std::forward<_U1>(__x)),
90  second(std::forward<_U2>(__y)) { }
91 
92  pair(pair&& __p)
93  : first(std::move(__p.first)),
94  second(std::move(__p.second)) { }
95 #endif
96 
97  /** There is also a templated copy ctor for the @c pair class itself. */
98  template<class _U1, class _U2>
99  pair(const pair<_U1, _U2>& __p)
100  : first(__p.first),
101  second(__p.second) { }
102 
103 #ifdef __GXX_EXPERIMENTAL_CXX0X__
104  template<class _U1, class _U2>
105  pair(pair<_U1, _U2>&& __p)
106  : first(std::move(__p.first)),
107  second(std::move(__p.second)) { }
108 
109  // http://gcc.gnu.org/ml/libstdc++/2007-08/msg00052.html
110  template<class _U1, class _Arg0, class... _Args>
111  pair(_U1&& __x, _Arg0&& __arg0, _Args&&... __args)
112  : first(std::forward<_U1>(__x)),
113  second(std::forward<_Arg0>(__arg0),
114  std::forward<_Args>(__args)...) { }
115 
116  pair&
117  operator=(pair&& __p)
118  {
119  first = std::move(__p.first);
120  second = std::move(__p.second);
121  return *this;
122  }
123 
124  template<class _U1, class _U2>
125  pair&
126  operator=(pair<_U1, _U2>&& __p)
127  {
128  first = std::move(__p.first);
129  second = std::move(__p.second);
130  return *this;
131  }
132 
133  void
134  swap(pair&& __p)
135  {
136  using std::swap;
137  swap(first, __p.first);
138  swap(second, __p.second);
139  }
140 #endif
141  };
142 
143  /// Two pairs of the same type are equal iff their members are equal.
144  template<class _T1, class _T2>
145  inline bool
146  operator==(const pair<_T1, _T2>& __x, const pair<_T1, _T2>& __y)
147  { return __x.first == __y.first && __x.second == __y.second; }
148 
149  /// <http://gcc.gnu.org/onlinedocs/libstdc++/manual/utilities.html>
150  template<class _T1, class _T2>
151  inline bool
152  operator<(const pair<_T1, _T2>& __x, const pair<_T1, _T2>& __y)
153  { return __x.first < __y.first
154  || (!(__y.first < __x.first) && __x.second < __y.second); }
155 
156  /// Uses @c operator== to find the result.
157  template<class _T1, class _T2>
158  inline bool
159  operator!=(const pair<_T1, _T2>& __x, const pair<_T1, _T2>& __y)
160  { return !(__x == __y); }
161 
162  /// Uses @c operator< to find the result.
163  template<class _T1, class _T2>
164  inline bool
165  operator>(const pair<_T1, _T2>& __x, const pair<_T1, _T2>& __y)
166  { return __y < __x; }
167 
168  /// Uses @c operator< to find the result.
169  template<class _T1, class _T2>
170  inline bool
171  operator<=(const pair<_T1, _T2>& __x, const pair<_T1, _T2>& __y)
172  { return !(__y < __x); }
173 
174  /// Uses @c operator< to find the result.
175  template<class _T1, class _T2>
176  inline bool
177  operator>=(const pair<_T1, _T2>& __x, const pair<_T1, _T2>& __y)
178  { return !(__x < __y); }
179 
180 #ifdef __GXX_EXPERIMENTAL_CXX0X__
181  /// See std::pair::swap().
182  // Note: no std::swap overloads in C++03 mode, this has performance
183  // implications, see, eg, libstdc++/38466.
184  template<class _T1, class _T2>
185  inline void
187  { __x.swap(__y); }
188 
189  template<class _T1, class _T2>
190  inline void
191  swap(pair<_T1, _T2>&& __x, pair<_T1, _T2>& __y)
192  { __x.swap(__y); }
193 
194  template<class _T1, class _T2>
195  inline void
196  swap(pair<_T1, _T2>& __x, pair<_T1, _T2>&& __y)
197  { __x.swap(__y); }
198 #endif
199 
200  /**
201  * @brief A convenience wrapper for creating a pair from two objects.
202  * @param x The first object.
203  * @param y The second object.
204  * @return A newly-constructed pair<> object of the appropriate type.
205  *
206  * The standard requires that the objects be passed by reference-to-const,
207  * but LWG issue #181 says they should be passed by const value. We follow
208  * the LWG by default.
209  */
210  // _GLIBCXX_RESOLVE_LIB_DEFECTS
211  // 181. make_pair() unintended behavior
212 #ifndef __GXX_EXPERIMENTAL_CXX0X__
213  template<class _T1, class _T2>
214  inline pair<_T1, _T2>
215  make_pair(_T1 __x, _T2 __y)
216  { return pair<_T1, _T2>(__x, __y); }
217 #else
218  template<typename _Tp>
219  class reference_wrapper;
220 
221  // Helper which adds a reference to a type when given a reference_wrapper
222  template<typename _Tp>
223  struct __strip_reference_wrapper
224  {
225  typedef _Tp __type;
226  };
227 
228  template<typename _Tp>
229  struct __strip_reference_wrapper<reference_wrapper<_Tp> >
230  {
231  typedef _Tp& __type;
232  };
233 
234  template<typename _Tp>
235  struct __strip_reference_wrapper<const reference_wrapper<_Tp> >
236  {
237  typedef _Tp& __type;
238  };
239 
240  template<typename _Tp>
241  struct __decay_and_strip
242  {
243  typedef typename __strip_reference_wrapper<
244  typename decay<_Tp>::type>::__type __type;
245  };
246 
247  // NB: DR 706.
248  template<class _T1, class _T2>
249  inline pair<typename __decay_and_strip<_T1>::__type,
250  typename __decay_and_strip<_T2>::__type>
251  make_pair(_T1&& __x, _T2&& __y)
252  {
253  return pair<typename __decay_and_strip<_T1>::__type,
254  typename __decay_and_strip<_T2>::__type>
255  (std::forward<_T1>(__x), std::forward<_T2>(__y));
256  }
257 #endif
258 
259 _GLIBCXX_END_NAMESPACE
260 
261 #endif /* _STL_PAIR_H */
pair holds two objects of arbitrary type.
Definition: stl_pair.h:67
bool operator==(const pair< _T1, _T2 > &__x, const pair< _T1, _T2 > &__y)
Two pairs of the same type are equal iff their members are equal.
Definition: stl_pair.h:146
pair(const pair< _U1, _U2 > &__p)
Definition: stl_pair.h:99
_T2 second
second is a copy of the second object
Definition: stl_pair.h:73
bool operator!=(const pair< _T1, _T2 > &__x, const pair< _T1, _T2 > &__y)
Uses operator== to find the result.
Definition: stl_pair.h:159
_T1 first_type
first_type is the first bound type
Definition: stl_pair.h:69
_T1 first
first is a copy of the first object
Definition: stl_pair.h:72
bool operator>=(const pair< _T1, _T2 > &__x, const pair< _T1, _T2 > &__y)
Uses operator< to find the result.
Definition: stl_pair.h:177
_T2 second_type
second_type is the second bound type
Definition: stl_pair.h:70
_OI move(_II __first, _II __last, _OI __result)
Moves the range [first,last) into result.
Definition: stl_algobase.h:491
bool operator>(const pair< _T1, _T2 > &__x, const pair< _T1, _T2 > &__y)
Uses operator< to find the result.
Definition: stl_pair.h:165
pair(const _T1 &__a, const _T2 &__b)
Definition: stl_pair.h:83