Question

I have a string 1.5(+1.2/-0.5). I want to use Regex to extract numerical value: {1.5, 1.2, 0.5}.

My plan is to split the string with (, +, / and -. When I do split with ( and /, it splits OK, but if I also add + and -, then program crashes.

string[] foo = Regex.Split("1.5(+1.5/-0.5)", @"(?=[(/)])");
// OK

string[] foo = Regex.Split("1.5(+1.5/-0.5)", @"(?=[(/+-)])"); 
// Exception catched

And the caught exception is:

System.ArgumentException: parsing “(?=[(/+-)])” – [x-y] range in
reverse order

Answer 1

The dash is a special character when inside square brackets in a regexp. It means a range: [a-z] means any character from a to z. When you wrote [(/+-)], it would actually mean (, or any character from + to ). The error comes from the fact that in ASCII ordering ) comes before +, so a character range [+-)] is invalid.

To fix this, dash must always come first or last when in brackets, or it needs to be backslashed.

And I agree, I’d probably use a global regexp to pick out [0-9.]+, and not a split to cut on everything else.