#include<iostream>

#include<iomanip>

using namespace std;

class point

{

public:

   void set();//设置原点坐标；；

   void move();//移动距离；

   void l(int x,int y);//移动后坐标及两点间距离；

   int getx();

   int gety();

private:

int x,y;

};

class line

{

public:

line(point a,point b);

   void xl();//直线的斜率；

private:

   point p1,p2;

};

main()

{

   class point a,b;

   class line l1(point a,point b);

   cout<<"请设置直线上两点坐标：";

   a.set();

   b.set();

   l1(a,b);

}

void point::set()

{

   cin>>x;

   cin>>y;

   cout<<"点坐标为:("<<x<<","<<y<<")"<<endl;

}

void point::move()

{

   int m,n;

   cin>>m;

   cin>>n;

   x=x+m;

   y=y+n;

   cout<<"移动后坐标为：("<<x<<","<<y<<")."<<endl;

   cout<<"两点间距离为："<<sqrt(m*m+n*n)<<endl;

}

int point::getx()

{

   return x;

}

int point::gety()

{

   return y;

}

line::line(point a,point b):p1(a),p2(b)

{

   double k;

   int m,n,p,q;

   p1=a;

   p2=b;

   m=p1.getx();

   n=p1.gety();

   p=p2.getx();

   q=p2.gety();

   k=(n-q)/(m-p);

   cout<<"直线的斜率为:"<<k<<endl;

}

组建错误：

unresolved external symbol "class line __cdecl l1(class point,class point)" (?l1@@YA?AVline@@Vpoint@@0@Z)