设计一个表示直角坐标系上点的位置的Location类，计算两个坐标系上点对象A和B之间的距离。要求用成员函数Distance（）求距离。在main（）中，分别用对象、指针、引用三种方法定义和使用对象A和B。-Said the design of a Cartesian coordinate system on the location of the point of Location categories, calculated on the two coordinate system object A and B points, the distance between. Requested by members of function Distance () for the distance. In the main () in, respectively, with targets, indicators, citing the definition of three methods and the use of object A and B.