Just a naive calculator which only support '+' '-' '*' '/' operators and expressions with bracket.
这只是一个超级简陋的计算器www
仅支持加、减、乘、除四则运算和带括号的表达式。
2022/3/8 version 1.0
2022/3/9 version 1.1
Repair the bug of nagative sign and blank input.
修复了空表达式和负数符号导致程序崩溃的问题。
2022/3/17 version 1.2
Repair the bug that the program will crash when the right bracket is linked together with a number.
修复了当右括号紧连着数字导致程序崩溃的问题。