I have a string that looks like this:
-2.2,1.1-6.9,2.3-12.8,2.3
And I want to write a function ParseString() which would return a list of doubles with these elements:
-2.2
1.1
-6.9
2.3
-12.8
2.3
The problem I have is that the minus sign is acting like a delimiter, but also has semantic meaning (signifies negative number). I am quite inexperienced with regular expressions and I am stuck on this. Can any expert out there help me out with this? I am writing this in C#.
You can split on the regex ,|(?<!^|,)(?=-).
Tested example:
var splitter = new Regex(@",|(?<!^|,)(?=-)");
var numbers = splitter.Split(@"-2.2,1.1-6.9,2.3,-12.8,2.3")
.Select(Double.Parse);
This regex matches either , or (?<!^|,)(?=-).
(?!^)(?=-) is a pair of zero-width assertions that matches before a - that isn't at the beginning of the string or after a comma.
(?<!^|,) is a negative lookbehind that prevents it from matching after the beginning of the string or a comma. Without this negation, it will return extra empty strings.
(?=-) is a positive lookahead that forces it to match right before a -.
A simple solution (not the most efficient) is to first replace "-" with ",-" and then split on "," and finally parse the parts. Like this:
string numStr = "-2.2,1.1-6.9,2.3-12.8,2.3";
string[] splitNumStr = numStr.Replace("-", ",-").Split(',');
List<double> nums = splitNumStr.Select(s => double.Parse(s)).ToList();
