设计一个分数类，表示分数。数据成员可以是分子、分母，成员函数包括构造函数、设置数据成员值的函数，显示分数的函数（显示形式：分子/分母）、分数的加法、分数的减法、分数的乘法、分数的除法，显示的分数应是最简的分数。-Design a fraction class, said the scores. Data members can be the numerator, denominator, member functions, including the constructor, set the function of the data member value, display the score function (display form: numerator/denominator), fraction addition, fraction subtraction, multiplication of fraction, fraction division the score displayed is the most simple score.