c++pair键值对

#include "iostream"

using namespace std;

template<class T1,class T2>
struct Pair
        {
    T1 first;
    T2 secondl;
    Pair(){
        cout<<"调用了有默认的构造函数。\n";
    }
    Pair(const T1&val1,const T2&val2):first(val1),secondl(val2)
    {
        cout<<"调用了有两个参数的构造函数。\n";
    }
    Pair(const pair<T1,T2>& p):first(p.first),secondl(p.second){
        cout<<"调用了拷贝构造函数。\n";
    }
};

template<class T1,class T2>
        Pair<T1,T2>make_Pair(const T1& first,const T2&second)
{
    Pair<T1,T2>p(first,second);
    return p;//返回局部对象
}


int main()
{
pair<int,string> p0;
cout<<"p0 first="<<",second="<<p0.second<<endl;

pair<int,string>p1(1,"西施1");//两个参数的构造函数。
cout<<"p1 first="<<p1.first<<",second="<<p1.second<<endl;

pair<int,string>p2=p1;//拷贝构造。
cout<<"p2.first="<<p2.first<<",second="<<p2.second<<endl;

pair<int,string>p3={3,"西施3"};//两个参数的构造函数。
cout<<"p3 first="<<p3.first<<",second="<<p3.second<<endl;

auto p4=pair<int,string>(4,"西施4");//匿名对象
cout<<"p4 first="<<p4.first<<",second="<<p4.second<<endl;

auto p5= make_pair<int,string>(5,"西施5");//make_pair()返回的临时对象。
cout<<"p5 fisrt"<<p5.first<<",second="<<p5.second<<endl;

pair<int,string>p6= make_pair(6,"西施6");//慎用，让make_pair()返回的临时东西。
cout<<"p6= fisrt="<<p6.first<<",second="<<p6.second<<endl;

auto p7= make_pair(7,"西施7");//慎用，让make_pair()函数.......
cout<<"p7 first="<<p7.first<<",second="<<p7.second<<endl;

p5.swap(p4);

cout<<"p4 first="<<p4.first<<",second="<<p4.second<<endl;
cout<<"p5 first="<<p5.first<<".second="<<p5.second<<endl;

struct st_girl
{
    string name;
    int age;
    double height;
};
//用pair存放结构体数据。
pair<int,st_girl> p ={3,{"西施",23,48.6}};
cout<<"p first="<<p.first<<endl;
cout<<"p second.naem="<<p.second.name<<endl;
cout<<"p second.age="<<p.second.age<<endl;
cout<<"p second.height"<<p.second.height<<endl;

}

输出：

p0 first=,second=
p1 first=1,second=西施1
p2.first=1,second=西施1
p3 first=3,second=西施3
p4 first=4,second=西施4
p5 fisrt5,second=西施5
p6= fisrt=6,second=西施6
p7 first=7,second=西施7
p4 first=5,second=西施5
p5 first=4.second=西施4
p first=3
p second.naem=西施
p second.age=23
p second.height48.6