Zugg Software :: View topic - [2.34] Nested alternations in string lists don't work for regexes

Adept Joined: 04 Feb 2005 Posts: 246

If you execute the following code:

Wizard Joined: 03 Mar 2001 Posts: 1127 Location: London

You could get around it using %concat
tmp = %concat(@tmp,|(?:b|c))

Adept Joined: 04 Feb 2005 Posts: 246

The above doesn't quite work because I need to use the variable in an RE, and I have it as a string list.

The point is that I use a string list as an aid to understanding the RE. The reason is that it's horribly complex as is... I suppose I could use a string instead, but the UI for the stringlist is much easier to manage.

And if you're curious, an RE to detect almost any non-emit MUSH pose is:

Wizard Joined: 17 Jun 2006 Posts: 1201

Why use "^(%%string(@tmp))"? Why not just make it "^(@tmp)"? It works just fine so the title of this thread is false.

#show a
#show b
#show c
#show ~"b~"

a
fired - a
b
fired - b
c
fired - c
"b"

Wizard Joined: 22 Mar 2007 Posts: 2320

If I'm understanding what you want to do with this, wouldn't the solution be to do:

Wizard Joined: 17 Jun 2006 Posts: 1201

No I don't think so. That's completely different from the stringlist "a|(?:b|c)".

Look at it this way, pretend a, b, and c are all different triggers placed in a stringlist, which is why he said earlier "and I sometimes used REs with such constructs (such as "on (?:his|her|its) phone")".

Like this for example:

Adept Joined: 04 Feb 2005 Posts: 246

What I really want is a string list that will turn into "Nearby|On (?:his|her|its) phone". Granted, I can use a string, or I could expand out the alternatives, but in actual use, there are greater than 10 alternatives in the string list, and the string list UI is good to keep it straight. (And it worked in zMUD).

As for oldguy2's question, when I use "^(@tmp)", I get a parse error as it tries to do the sorting that Zugg has mentioned elsewhere (but that I disagree with anyways).

FYI, without the %%string(), using the RE I mentioned ("Nearby..."), I fail to match "Nearby" like it should. And because of the sorting, I can't see what the pattern it is actually trying (the compiled pattern tab just shows a var reference, and not the result)
Edit: Ah, the test tab shows me that by using just (@tmp), the pattern is turning into "^(On (?:his|Nearby|her) phone)".

Wizard Joined: 17 Jun 2006 Posts: 1201

Zhiroc see my example above. I have every single trigger that triggers the same action in stinglists, and some are pretty complicated with nested alternations. Maybe you need to reload 2.34?

I get "^(On (?:his|her|its) phone|Nearby)"

Edit: Hrm...you know what, I didn't reload the newer 2.34 after he took out the mapping, but I don't think that did anything. So I have the first version of 2.34 on my system. Try reloading your version see if it works. If not, then maybe whatever he did messed it up again?

Adept Joined: 04 Feb 2005 Posts: 246

Hmm, I downloaded 2.34 last night, but something's wrong... Yeah, I better reinstall, just in case...

Adept Joined: 04 Feb 2005 Posts: 246

OK, yes, after reloading 2.34, the "^(@tmp)" regex works fine (other than the reordering). However, if I ever wanted to preserve the order of the stringlist, using %%string() as outlined in the other thread, it doesn't work, as quotes are inserted around the nested alternation.

Wizard Joined: 17 Jun 2006 Posts: 1201

So don't put it in a variable. Just put the whole thing in the trigger pattern?

Posted: Wed Jul 30, 2008 7:57 pm

Wizard Joined: 22 Mar 2007 Posts: 2320

This is slightly off-topic, but I'd like to understand. A couple people have implied that {a|b|c} is not the same as {a|(?:b|c)}, but it looks to me that they are logically equivalent. Or did you just mean that the more general issue of nested alternations is a problem?

Adept Joined: 04 Feb 2005 Posts: 246

It is equivalent, I think (though technically the backtracking might be different, but I think even here it's the same).

However, this was a simple case. The actual case of interest was more complicated, and as soon as you add any wildcards or other text around the non-capture group, or make it a capture group, it's different. For example:

(a|(?:b|c)+)
(a|(?i:b|c))
(a|(b|c))
(a|x(?:b|c))

are all distinctly different than (a|b|c)

Wizard Joined: 17 Jun 2006 Posts: 1201

Yeah sorry Rahab. I said it wasn't the same because of what he was really referring to outside of the very simple example he posted. I guess he explained it above this post though. Sorry to confuse folks.

Wizard Joined: 22 Mar 2007 Posts: 2320

That's all right. Once I realized that Zhiroc was worried about the more general case, I knew that my simplistic answer was not useful. I just wanted to be sure my understanding of the regex was correct and that they were logically equivalent. Thanks!