#include <iostream>
using namespace std;
template <typename T> //这里前向声明了模板类Grid
class Grid;
template <typename T> //这里声明模板重载<<操作符的函数
ostream & operator << (ostream &os, const Grid<T> &grid);
template <typename T>
class Grid
{
public://现在我们就可以定义输出操作符的特化了
friend ostream & operator << <T>(ostream &os, const Grid<T> &grid);
};
int main (void)
{
Grid<int> test;
return 0;
}