用动态链表实现求凸壳的程序（卷包裹法），供三角网实现编程的人参考-Using dynamic list for the Convex Hull of the realization of procedures (vol Parcel law) for the triangular network programming reference

画图版，链表功能。undo，redo 实现文件的存取Open、New、Save、SaveAs 建立类，shape rectangle，circle，line类 -Paint version feature list. undo, redo implementation document access Open, New, Save, SaveAs type set up, shape rectangle, circle, line type