源程序：
#include <iostream>
using namespace std;
class point
{
private:
float x;
public:
void f(float a)
{
x = a;
}
void f()
{
x = 0;
}
friend float max(point &a,point &b);
};
float max(point &a, point &b)
{
return (a.x > b.x) ? a.x : b.x;
}
int main()
{
point a, b;
a.f(2.2);
b.f(3.3);
cout << max(a, b) << endl;
system("pause");
return 1;
}
运行结果：
