#include <stdafx.h>
#include <iostream.h>
#include <cmath>
class Point
{
       double x;
       double y;
public:
       Point(double a,double b)
       {
              x=a;
              y=b;
       }
       friend double dist(Point a,Point b);
};
double dist(Point a,Point b)
{
     return sqrt((a.x-b.x)*(a.x-b.x)+(a.y-b.y)*(a.y-b.y));
}
void main()
{
     Point p1(1,2);
     Point p2(5,2);
     cout<<dist(p1,p2)<<endl;
}

将友元函数dist(point a,point b)改为Point类的公有成员函数 Point ::dist(point &b)，请修改主函数中的相应代码时程序功能不变。