模仿windows计算器，通过for循环实例化按钮，设置BoxLayout，通过if控制记录被运算数和运算数。通过if控制求导运算、开根号运算、删除键-Mimic the windows calculator for loop to instantiate button, set the BoxLayout operands and operands, if control records. If control of the derivative operator, the square root operator, the delete key