|
#2
lijm19892010-06-05 12:54
 程序代码：#include<iostream> using namespace std; template <class T> class test { friend ostream &operator << <T>(ostream &out,test<T>& t); public: T x,y; }; template <class T> ostream & operator << (ostream &out,test<T>& t) { out<<t.x<<t.y; return out; } 程序代码：#include<iostream> using namespace std; template <class T> class test { template <class U> friend ostream &operator << (ostream &out,test<U>& t); public: T x,y; }; template <class T> ostream & operator << (ostream &out,test<T>& t) { out<<t.x<<t.y; return out; } #include<iostream> using namespace std; template <class T> class test { friend ostream &operator << (ostream &out,test<T>& t); public: T x,y; }; template <class T> ostream & operator << (ostream &out,test<T>& t) { out<<t.x<<t.y; return out; } 友元函数不属于类成员，模板函数的友元声明模板在使用之前必须先声明。模板的使用由友元声明构成，不是由模板的声明构成。实际的模板声明必须在友元声明之前。 |
#include<iostream>
template <class T>
class test
{
friend std::ostream & operator <<(std::ostream &out,test& t)
{
out<<t.x<<t.y;
return out;
}
public:
T x,y;
};
在这个程序里，如果把友元函数在类外定义就会出现连接错误，谁能解释一下？？我用的是vs2005。
