#include<iostream>
#include<string>
#include<utility>
using namespace std;

template <typename T>
int compare(const T &a ,const T &b)
{
    if(a<b) return -1;
    if(b<a) return 1;
    return 0;
}

template <typename T>
auto sum(T a,T b)->decltype(a+b)
{
    return a+b;
}
//翻转函数
template<typename F,typename T1,typename T2>
void flip(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;
}
int main()
{
    int j=8;
    compare<const char*>("hi","world");
    flip(f,j,42);
    cout<<j<<endl;
    flip(g,j,42);
}