模板类的友元重载函数

#include <iostream>

using namespace std;

template<class T>

class Test 

{

public:

friend ostream& operator << <> (ostream& out, const Test<T>& obj);

Test(T n=0):num(n){}

Test(const Test<T>& copy)

{

num = copy.num;

}

private:

T num;

};

template<class T>

ostream& operator << <> (ostream& out, const Test<T>& obj)

{

out<<obj.num<<endl;

return out;

}

int main()

{

Test<int> t(2);

cout<<t;

return 0;

}

或者是

#include <iostream>

using namespace std;

template<class T>

class Test 

{

public:

 template<class T>

friend ostream& operator << (ostream& out, const Test<T>& obj);

Test(T n=0):num(n){}

Test(const Test<T>& copy)

{

num = copy.num;

}

private:

T num;

};

template<class T>

ostream& operator << (ostream& out, const Test<T>& obj)

{

out<<obj.num<<endl;

return out;

}

int main()

{

Test<int> t(2);

cout<<t;

return 0;

}