stl_pair.h

/*
 *
 * Copyright (c) 1994
 * Hewlett-Packard Company
 *
 * Permission to use, copy, modify, distribute and sell this software
 * and its documentation for any purpose is hereby granted without fee,
 * provided that the above copyright notice appear in all copies and
 * that both that copyright notice and this permission notice appear
 * in supporting documentation.  Hewlett-Packard Company makes no
 * representations about the suitability of this software for any
 * purpose.  It is provided "as is" without express or implied warranty.
 *
 *
 * Copyright (c) 1996,1997
 * Silicon Graphics Computer Systems, Inc.
 *
 * Permission to use, copy, modify, distribute and sell this software
 * and its documentation for any purpose is hereby granted without fee,
 * provided that the above copyright notice appear in all copies and
 * that both that copyright notice and this permission notice appear
 * in supporting documentation.  Silicon Graphics makes no
 * representations about the suitability of this software for any
 * purpose.  It is provided "as is" without express or implied warranty.
 */

/* NOTE: This is an internal header file, included by other STL headers.
 *   You should not attempt to use it directly.
 */

#ifndef __SGI_STL_INTERNAL_PAIR_H
#define __SGI_STL_INTERNAL_PAIR_H

__STL_BEGIN_NAMESPACE

template <class _T1, class _T2>
struct pair {                                         //pair是一个键值对
  typedef _T1 first_type;                             //键值对第一项，一般是键值
  typedef _T2 second_type;                            //键值对第二项，一般是实值

  _T1 first;                                          //注意，first是public的
  _T2 second;                                         ////注意，second也是public的
  pair() : first(_T1()), second(_T2()) {}
  pair(const _T1& __a, const _T2& __b) : first(__a), second(__b) {}

#ifdef __STL_MEMBER_TEMPLATES
  template <class _U1, class _U2>
  pair(const pair<_U1, _U2>& __p) : first(__p.first), second(__p.second) {}
#endif
};

template <class _T1, class _T2>
inline bool operator==(const pair<_T1, _T2>& __x, const pair<_T1, _T2>& __y)
{ 
  return __x.first == __y.first && __x.second == __y.second; 
}

template <class _T1, class _T2>
inline bool operator<(const pair<_T1, _T2>& __x, const pair<_T1, _T2>& __y)
{ 
  return __x.first < __y.first || 
         (!(__y.first < __x.first) && __x.second < __y.second); 
}

#ifdef __STL_FUNCTION_TMPL_PARTIAL_ORDER

template <class _T1, class _T2>
inline bool operator!=(const pair<_T1, _T2>& __x, const pair<_T1, _T2>& __y) {
  return !(__x == __y);
}

template <class _T1, class _T2>
inline bool operator>(const pair<_T1, _T2>& __x, const pair<_T1, _T2>& __y) {
  return __y < __x;
}

template <class _T1, class _T2>
inline bool operator<=(const pair<_T1, _T2>& __x, const pair<_T1, _T2>& __y) {
  return !(__y < __x);
}

template <class _T1, class _T2>
inline bool operator>=(const pair<_T1, _T2>& __x, const pair<_T1, _T2>& __y) {
  return !(__x < __y);
}

#endif /* __STL_FUNCTION_TMPL_PARTIAL_ORDER */

template <class _T1, class _T2>
inline pair<_T1, _T2> make_pair(const _T1& __x, const _T2& __y)
{
  return pair<_T1, _T2>(__x, __y);
}

__STL_END_NAMESPACE

#endif /* __SGI_STL_INTERNAL_PAIR_H */

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