c++ std::forward

#include<iostream>
#include<utility>
using namespace std;
template<typename F,typename T1,typename T2>
//采用引用折叠方式,使其对所有方式参数适用
void filp(F f, T1 &&t1, T2 &&t2)
{
f(std::forward<T2>(t2), std::forward<T1>(t1));
}
void f(int v1, int &v2)
{
cout << v1 << " " << ++v2 << endl;
}
void g(int &&i, int j)
{
cout << i << " " << j << endl;
}
//g(int &&i,int j)第一个参数是右值，第二个参数是左值
//当我们想传递参数时,会因为引用折叠导致左值(右值)变右值(左值)等问题
//此时可通过std::forward获得本来想传递的参数
int main()
{
int a = 1, b = 2;
filp(f, a, b);
cout << a << ends << b << endl;
filp(g, a, 42);
system("pause");
return 0;
}