可以检查用户输入表达式是否正确的计算器，用户输入表达式（任意），通过判断表达式的正确与否给出相应的提示或者给出值，并记录在文件中方便查询-You can check whether the user entered the correct expression calculator, the user input expression (arbitrary), by judging whether or not to give the correct expression Prompt or