使用正则表达式解析数学表达式

Question

I want to parse a math expression using regular expression. For instance, the expression "-4-2-1" is parsed into "-4", "-", "2", "-" and "1". However, from my regex, I can only get "-", "4", "-", "2", "-", "1"

this is my regex ^-?\\d*\\.{0,1}\\d+$|[+-×÷^√∛!πe%]

Answer 1

You can't create regex for all kind of equations, but for your case you can improve your regex by

• making ^- part optional,
• escaping - in your character class (otherwise it will be treated as range operator)

BTW {0,1} can be replaced with ? .

So try with "(^-)?\\\\d*\\\\.?\\\\d+|[+\\\\-×÷^√∛!πe%]"