有如下类的定义。类成员函数copy用于实现两个对象的相互拷贝，请完成该函数的实现采用友元函数实现

#include <iostream>
using namespace std;
class Myclass 
{
public:
        Myclass (int a,int b) { x=a;y=b;}
        friend void copy(Myclass & ,Myclass &);
        void print( )
            { cout<<"x= "<<x<<endl;
              cout<<"y= "<<y<<endl;
            } 
private:
        int x,y;
};
void copy(Myclass & my,Myclass & my1)
{
   my.x=my1.x;
   my.y=my1.y;
}
int main()
{
    Myclass m1(1,2);
    Myclass m2(3,4);
    copy(m1,m2);
    m1.print();
    return 0;
}