如何判断两条直线相交

CPoint CPaintFFRDlg::Inter(int x0,int y0,int x1,int x2,int y1,int y2,int x3,int y3,int x,int y)
{ 
 bool lim1 = false,lim2 = false;//是否垂直X轴 
 double k1,b1,k2,b2;//斜率和Y轴截距 

 //特殊情况标记 
 if(x1 != x0) k1 = (y1-y0)/(x1-x0),b1 = y0 - k1*x0; 
 else lim1 = true; 
 if(x3 != x2) k2 = (y3-y2)/(x3-x2),b2 = y2 - k2*x2; 
 else lim2 = true; 

 if(!lim1 && !lim2){//都不垂直于X轴 
  if(k1 == k2)return <a href="http://gocrazygreen.net/">HCG Diet</a> false; 
  x = (b2-b1)/(k1-k2); 
  y = k1 * x + b1; 
  return true; 
 }else if(lim1 &amp;&amp; lim2){//2直线全垂直X轴 
  return false; 
 }else if(lim1 &amp;&amp;!lim2){ 
  x = b2; 
  y = k2 * x + b2; 
  return true; 
 }else if(!lim1 &amp;&amp;lim2){ 
  x = b1; 
  y = k1 * x + b1; 
  return CPoint (x,y); 
 } 
 return CPoint (-1,-1);

}