QT编写功能及界面，实现功能：加、减、乘、除、连加、连减、连乘、连除、加减乘除混合运算、除零报错等功能，代码简单清晰，适用于刚刚接触QT的人-QT write functions and interface functionality: add, subtract, multiply, divide, even increase, even less, and even multiply, even in addition, subtraction, multiplication and division mixed operations, in addition to the zero error function, the code is simple and clear, suitable for just contact The QT