说明：  有理数运算程序 设计内容：有理数是一个可以化为一个分数的数，例如2/3，533/920，-12/49都是有理数。在C++中，并没有预先定义有理数，该课程设计要求定义一个有理数类，将有理数的分子和分母分别存放在两个整型变量中，模拟进行针对有理数的各种操作。
(RATIONAL programming content: is a rational number can be reduced to a fraction of the number, say 2/3, 533/920,-12/49 are rational numbers. In C++, there is no pre-defined rational number, the course design to define a rational number class, will be the numerator and denominator of rational numbers are stored in two integer variables, the simulation carried out various operations for rational numbers.)