友元函数(二)

#include <iostream>
using namespace std;
class A
{
private:
int x,y;
public:
A(int i,int j) {x=i;y=j;}
int getX() {return x;}
int getY() {return y;}
friend class B;
};

class B
{
private:
int z;
public:
int add(A a) {return a.x+a.y+z;}
int mul(A a) {return a.x*a.y*z;}
B(int i=0) {z=i;}
};

void main()
{
A a(2,3);
B b(4);
cout<<b.add(a)<<endl;
cout<<b.mul(a)<<endl;
}