Regex issue using ICU regex to find numbers not inside parentheses

I'm trying to scan a given string for a number. The number cannot be after "v/v./vol/vol.", and cannot be inside parentheses. Here's what I have:

NSString *regex = @"(?i)(?<!v|vol|vol\\.|v\\.)\\d{1,4}(?![\\(]{0}.*\\))";
NSLog(@"Result: %@", [@"test test test 4334 test test" stringByMatching:regex]);
NSLog(@"Result: %@", [@"test test test(4334) test test" stringByMatching:regex]);
NSLog(@"Result: %@", [@"test test test(vol.4334) test test" stringByMatching:regex]);

Infuriatingly, this does not work. My regex can be separated into four parts:

(?i) - make r开发者_如何转开发egex case insensitive

(?<!v|vol|vol\\.|v\\.) - negative look-behind assertion for v/v./vol/vol.

\\d{1,4} - the number I'm looking for, 1-4 digits.

(?![\\(]{0}.*\\)) - negative look-ahead assertion: number cannot be preceding a ), unless there's a ( before it.

Maddeningly, if I take out the look-behind assertion, it works. What's the issue here? I'm using RegexKitLite, which uses the ICU regex syntax.

Your negative lookbehind is positioned incorrectly. Lookbehind's do not modify the input position, your negative lookbehind should come after your \d{1,4} expression:

(?i)\\d{1,4}(?<!v|vol|vol\\.|v\\.)(?![\\(]{0}.*\\))

Alternatively, just use a negative lookahead to accomplish the same purpose:

(?i)(?!v|vol|vol\\.|v\\.)\\d{1,4}(?![\\(]{0}.*\\))

Finally ended up with this regex:

(?i)\\d{1,4}(?<!v|vol|vol\\.|v\\.)(?![^\\(]*\\))

The negative look-behind needed to change. Passes all my tests. Thanks to Alex for identifying the positioning of my NLB being wrong.