可变参数模板

1，基础应用

#include<iostream>
#include<string>
#include<sstream>
using namespace std;
template<typename... Args> void g(Args... args)
{
    cout<<sizeof...(Args)<<endl;    //类型参数的数目
    cout<<sizeof...(args)<<endl;    //函数参数的数目
}

template<typename T>
string f(T t)
{
    cout<<"f()"<<endl;
    ostringstream strm;
    strm<<t<<'-'<<t<<endl;
    cout<<strm.str();
    return strm.str();
}
template<typename T>
ostream &print(ostream &os, const T &t)
{
    cout<<"p1()"<<endl;
    return os<<t;
}
template<typename T, typename... Args>
ostream &print(ostream &os, const T &t, const Args&... reset)
{
    cout<<"p2()"<<endl;
    os<<t<<", ";
    //return print(os, reset...);
    return print(os, f(reset)...);
}

int main()
{
    g();
    g(1);
    g(1, 1.2);
    g(1, 1.2, "hello");

    print(cout, 1, 3.4, "hello");
    cout<<endl;
    return 0;
}

　　重点理解其递归调用

2，