定义一个Shape抽象类，在此基础上派生出Rectangle和circle类，二者都有GetArea（）函数计算对象面积，GetPerim（）函数计算对象的周长。使用Rectangle类派生出一个新类Squre。-The definition of an abstract class Shape, on the basis of derived type Rectangle and circle, both have GetArea () function the object area, Ge