用来求解有理数分式方程。为它设计两个数据成员，一个作为分子，另一个作为分母。分母不能为0。有理数1/2可以使用这个类的对象r表示为r(1,2)。需要完成如下操作：

如果分子和分母友公约数，就应该进行化简；

有理数可以进行四则运算，需要重载运算符；

重载流运算符，可以直接输入分子和分母，以及作为整体输出

-Used for solving the rational fraction equation. For its design two data members, a as a molecular, another as the denominator. The common denominator can t is 0. The rational number 1/2 can use an object of this class r said to r (1, 2). Need to complete the following operation:

If the molecules and denominator when friends, should be reduction

The rational number can be arithmetic, need to override operator

Overloaded operators, can be directly flow input molecule and denominator, as well as the overall output