Zugg Software :: View topic - RegEx named capturing group in Trigger Patterns

Beginner Joined: 09 Jul 2012 Posts: 11

Does anyone know if there is a way to refer to a named capturing group from a trigger pattern?

For example:

Sorcerer Joined: 15 Apr 2011 Posts: 809

Try %param(dirs).

Beginner Joined: 09 Jul 2012 Posts: 11

Good thought - but that didn't work. That is just returning the entire line, which is the same as using %param(). Any other thoughts?

Posted: Thu Aug 02, 2012 5:31 pm

As far as I know, the regex itself is supported, but named captures are not within zscript. If you find a way, let me know. I've got a friend who has been dying to do that.

Sorcerer Joined: 15 Apr 2011 Posts: 809

That's strange, it works fine for me... This is the trigger I'm testing with:

Posted: Thu Aug 02, 2012 7:32 pm

Oh, very interesting. I'll have to add that to my internal knowledge. :D

Beginner Joined: 09 Jul 2012 Posts: 11

OK. I played around with this a bit and realized what it is doing. %param(<type anything or nothing here>) is simply concatenating all of the capture groups and returning that string. For this purpose, the reason %param(dirs) was working for you, but not for my testing, is because you only had one capture group.

I was testing with multiple capture groups, which essentially captured the whole line, but in separate chunks. When I called %param(dirs), it was returning each of the parameters, but it appeared to me that it was the whole line. If you were to take your test and call %param(nonsensetest) or %param(), you'd still see 'foo', because it is the only thing you captured.

So, while %param does return values, it is still not exactly what I'm looking for. I suppose cMUD could have been coded to play nice with named capture groups, but not provide a way to reference them. That just seems a bit silly to me if that is the case.

Sorcerer Joined: 15 Apr 2011 Posts: 809

Hmm, you're right. That feels buggy to me.

Wizard Joined: 22 Mar 2007 Posts: 2320

It's not exactly buggy. It was simply trying to interpret "dir" as an integer, which to Cmud evaluated as %null, so it was the equivalent of %param(). The problem is, as Charneus said, Cmud does not implement named capturing groups. You need to use %1 or %param(1) in Cmud.

GURU Joined: 23 Dec 2000 Posts: 4834 Location: USA

Not in regex, at least. Zscript patternmatching (moreorless regex made easy) has a way to apply a name to your capture group:

#trigger {...($varname:pattern goes here)...}

Posted: Fri Aug 03, 2012 7:55 pm

So based on what Matt said how about

Beginner Joined: 09 Jul 2012 Posts: 11

Posted: Sun Aug 05, 2012 11:25 am

Except that is RegEx and captures whatever pattern is in the parenthesis to the variable @dirs it is just a slight modification of yours, ?<dirs> becomes ?dirs: instead.

Beginner Joined: 09 Jul 2012 Posts: 11

Thanks Taz. I don't have any trouble doing this in zscript, but the point of the thread was to see if RegEx supports the named capture groups, not translating it to zscript. I was hoping it would so that I could make use of name backreferences in the regex pattern and also be able to more clearly utilize the capture groups in complex patterns. My "Exits" line was just an example for familiarity and simplicity's sake.

EDIT: I should apologize, Taz. I went back and reread your post and it made perfect sense this time. Not sure why I didn't understand clearly the first time, but your solution does, in fact, work perfectly fine with RegEx for named capturing groups. Thank you!!