Question

C++友元函数求两点间距离，改错！

#include<math.h>
#include<iostream>
using namespace std;
class CPoint
{
private:
double x,y;
public:
void set(double xx,double yy)
{
cin>>xx>>yy;
x=xx;y=yy;
}
friend double distance(CPoint &a,CPoint &b);
};
double distance(CPoint &a,CPoint &b)
{
double l;
l=sqrt((a.x-b.x)*(a.x-b.x)+(a.y-b.y)*(a.y-b.y));
return l;
}
int main()
{
CPoint p1,p2;
double a,b,c,d,n;
p1.set(a,b);
p2.set(c,d);
n=distance(p1,p2);
cout<<"Distance="<<n<<endl;
return 0;
}

Answer 1

你把你的友元函数名修改成distance_new
因为那个名字在std，名字空间里面已经用了

Answer 2

distance(_InIt _First, _InIt _Last)
标准库里面也有个distance()函数，调到该函数执行了