想知道怎么调试vc6.0

问题遇到的现象和发生背景

使用的是vc6.0发生了错误，应该是要调试，想知道怎么调试

问题相关代码，请勿粘贴截图

#include<iostream>
using namespace std;
#include<cmath>
class point
{
    
private:
    double m_x,m_y;
public:
    
    point(double x,double y)
    {
        m_x=x;
        m_y=y;
    }

    void setxy()
    {
        cout<<"("<<m_x<<","<<m_y<<")"<<endl;
    }
    friend double distance(point p1,point p2);

};
double distance(point p1,point p2)
{
    
    double x=p1.m_x-p2.m_x;
    double y=p1.m_y-p2.m_y;
    return sqrt(x*x+y*y);
}
int main()
{
    point a(3,4),b(4,5);
    
    double n=distance(a,b);

    a.setxy();b.setxy();

    cout<<"距离为："<<n<<endl;

    return 0;
}

运行结果及报错内容

error C2785: 'int __cdecl std::distance(_II,_II)' and 'double __cdecl distance(class point,class point)' have different return types
c:\文件下载\microsoft visual studio\vc98\include\utility(100) : see declaration of 'distance'

我的解答思路和尝试过的方法

我想要达到的结果

    double n=distance(a,b);
----》
    double n=::distance(a,b);