说明：  计算几何大全，c++代码，内含点，直线，线段，圆，弧，多边形等求交，相互关系等等各种算法，对CAD等编程有很大帮助
(computational geometry Daquan, c code, intron, straight line, circle, arc, polygon, etc. intersection, mutual relations, and so on various algorithms, such as the CAD program is very helpful)