support negative number

[Nice2008]

1. Support such as: "-1*(-2)"

[W-Mai]

I test your code, but get

-1*(-2);
[Syntax Error]: -.

Another grammatical error appears. Similarly, if we try the following code,

-sin(30)

There will be the same result. Maybe we need to modify - at the grammatical analysis level.

Are you interested in delving into it and continuing to modify it? Let's discuss together.