定义三维坐标的Point类。包含一个构造函数，一个拷贝构造函数，一个将点变为负值的函数negate()，一个返回该点到原点（0，0，0）距离的函数norm()和一个输出点坐标的函数print（）。并定义一个静态数据成员记录创建点的个数。-definition three-dimensional coordinates of the Point class. Includes a constructor function, a copy constructor, to a point into negative negate the function (), a return to the point of origin (0,0, 0) function from the norm (), and an output function coordinates print (). And the definition of a static data member creation record number of points.