点积的模板
double dotdet(double x1,double y1,double x2,double y2)
{
return x1*x2+y1*y2;
}
double dot(point a,point b,point c)
{
return dotdet(a.x-c.x,a.y-c.y,b.x-c.x,b.y-c.y);
}
int betweenCmp(point a,point b,point c)
{
return dblcmp(dot(a,b,c));
}计算几何：点积的模板
原文：http://blog.csdn.net/guoxianzhuang/article/details/44625625
