stl之pair简介
原载:http://hi.baidu.com/taozpwater/item/d85d81bde4fd154b2bebe34e
1、简介
class pair ,中文译为对组,可以将两个值视为一个单元。对于map和multimap,就是用pairs来管理value/key的成对元素。任何函数需要回传两个值,也需要pair。
该函数的相关内容如下所示:
|->Type----->struct
|->Include---> <utility>
|->Define----> pair<calss first,calss second>(first,second)
|
|->member
| |------>first
| |------>second
|
|->Sub
| |------>constructor(default,assignment,copy)
|
|->Fun
|------>operator(==,<,<=,>,>=,!=,=)
|------>make_pair(first,second) 返回一个新的pair
需求:
Header: <utility>
Namespace: std
2、stl源码
pair的源码
// TEMPLATE STRUCT pair
template<class _Ty1,
class _Ty2> struct pair
{// store a pair of values
typedef pair<_Ty1, _Ty2> _Myt;
typedef _Ty1 first_type;
typedef _Ty2 second_type;
pair()
: first(_Ty1()), second(_Ty2())
{// construct from defaults
}
pair(const _Ty1& _Val1, const _Ty2& _Val2)
: first(_Val1), second(_Val2)
{// construct from specified values
}
template<class _Other1,
class _Other2>
pair(const pair<_Other1, _Other2>& _Right)
: first(_Right.first), second(_Right.second)
{// construct from compatible pair
}
void swap(_Myt& _Right)
{// exchange contents with _Right
if (this != &_Right)
{// different, worth swapping
std::swap(first, _Right.first);
std::swap(second, _Right.second);
}
}
_Ty1 first;// the first stored value
_Ty2 second;// the second stored value
};
makepair的源码
template<class _Ty1,
class _Ty2> inline
pair<_Ty1, _Ty2> make_pair(_Ty1 _Val1, _Ty2 _Val2)
{// return pair composed from arguments
return (pair<_Ty1, _Ty2>(_Val1, _Val2));
}
3、使用范例
#include <utility>
#include <stdio.h>
using namespace std;
int main()
{
pair<char, int> c1(L'x', 3);
printf("[%c, %d", c1.first, c1.second);
c1 = make_pair(L'y', 4);
printf("[{%c}, {%d}]", c1.first, c1.second);
return (0);
}