I've been using search to find questions that don't have a tag for a winning criterion (https://codegolf.meta.stackexchange.com/a/908/3808), and here's the search query I have so far:


I know, quite large. Anyway, of the 95 posts that it finds, I've noticed that some are tagged and some are tagged , and it seems to be pretty inconsistent. Some of them are even tagged with both!

So, my question is: do we really need ? Can't it just be merged or synonymized with (and then maybe also tagged with )?

Edit: based on the answer, probably shouldn't be a tag. This is now an explicit synonym request: could become a synonym of ?

  • \$\begingroup\$ The way to make a synonym request is via http://codegolf.stackexchange.com/tags/the-tag/synonyms. \$\endgroup\$ Jan 28, 2014 at 17:45
  • \$\begingroup\$ @PeterTaylor I don't have enough tag score for this tag, though. \$\endgroup\$
    – Doorknob
    Jan 28, 2014 at 17:58
  • \$\begingroup\$ Ah, ok. I've suggested it for you. \$\endgroup\$ Jan 28, 2014 at 18:14
  • \$\begingroup\$ @PeterTaylor Thanks, but it's supposed to be the other way (regex-golf => regular-expression)... \$\endgroup\$
    – Doorknob
    Jan 30, 2014 at 2:55
  • \$\begingroup\$ Oops! That's what I was trying to do, but I bodged it. We're going to need two people to downvote the current suggestion before anyone can create the correct one. \$\endgroup\$ Jan 30, 2014 at 8:36
  • \$\begingroup\$ @PeterTaylor: Downvoted. But I suspect it would be easier to just re-tag the questions by hand. \$\endgroup\$ Feb 1, 2014 at 14:04
  • \$\begingroup\$ @Ilmari Well, we want people to be redirected to [regular-expression] when they type [regex-golf]. This would be much easier with the help of a mod, but I've already flagged for one a while ago and the flag's still active. \$\endgroup\$
    – Doorknob
    Feb 1, 2014 at 14:05
  • \$\begingroup\$ I was going to say that the xkcd-inspired regex golf craze is probably mostly over by now, but on the other hand, it does occur to me that having a synonym of regular-expression with the substring "regex" in it could be a good thing regardless. \$\endgroup\$ Feb 1, 2014 at 14:08
  • \$\begingroup\$ I started it, but for some reason my vote is not binding. \$\endgroup\$ Feb 12, 2014 at 3:35
  • \$\begingroup\$ @dmckee Hmm, that's odd. Don't know why that would happen... anyway, thanks! (I just made a meta post) \$\endgroup\$
    – Doorknob
    Feb 12, 2014 at 3:38
  • \$\begingroup\$ @dmckee Found out why - meta.stackexchange.com/q/202228/180276 \$\endgroup\$
    – Doorknob
    Feb 12, 2014 at 3:55
  • \$\begingroup\$ Ah...thanks. I'll just go fix that now. \$\endgroup\$ Feb 12, 2014 at 3:56

2 Answers 2


We had this today with a regex golf question.

I agree with the previous answer that is superfluous and such questions should be tagged and .

However, I do not agree with the conclusion being that and are synonyms. For one thing, there could be challenge that are not code-golf, but since is the parent tag of the two, that maybe isn't a problem semantically.

However, it's a problem practically. At least 3 users (including myself) tried to edit the above question today, by removing and adding , because the latter still shows up in the auto-complete list. There is no indication though that this is a synonym for . So while you're editing, you see them both and think "Nice, I tagged this more appropriately" (seeing we can't expect everyone to be aware of this here meta question) - but when you submit, your tag suddenly vanishes, and the challenge is left without a winning criterion.

Even if it's just to avoid such edit frenzies in the future, I suggest to

  • \$\begingroup\$ +1 for practicality. Watching multiple users make a mistake should be more than enough reason to fix it. I can't even figure out how to disassociate them. I suppose a mod has to do that? \$\endgroup\$
    – Rainbolt
    May 29, 2014 at 18:57
  • 1
    \$\begingroup\$ Done. Tags merged, synonym removed. \$\endgroup\$
    – Doorknob
    May 29, 2014 at 22:05

We do have some challenges correctly tagged with + that don't count as in the sense described in the tag wiki:

"Regex golf is a programming challenge involving two lists of items. The goal is to create a regex that matches one list without matching anything in the second."

Some past challenges that are code golf and do involve regexps, but don't fall under the definition above (even in a loose sense), include:

  • Negative Regexp:

    "Write the shortest function that takes one string, and returns a regular expression that matches anything EXCEPT the input string, in parenthesis."

  • Compile Regexes:

    "In this task you have to write a program that reads a regular expression and generates another program that outputs whether an input string is accepted by that regular expression."

  • Convert Regexes:

    "Suppose you have existing regexes you wish to compile using one of the submissions to Compile Regexes. In as few characters as possible, write a program to make that work:"

All these are code golf challenges where the input or output of the golfed code, rather than the code itself, is a regular expression. So, IMO, we could meaningfully declare that should be used for code golf challenges where the code being scored is a regexp, while would be reserved for challenges involving manipulation of regexps.

On the other hand, we could also equally well decide that this distinction is not a useful one to make, and that should be replaced with +. In fact, I'm personally somewhat inclined in this direction myself, even if it does make the tag slightly more ambiguous.

(In any case, the same ambiguity arises also with the other language tags, which can mean either "this challenge is restricted to language X" or "this challenge is about parsing / interpreting / generating language X, but you can use any language to do that". Most of those languages don't have separate tags for these two purposes, and I don't think adding such tags would really be desirable, either.)

  • 1
    \$\begingroup\$ I agree, [regular-expression] is basically just a language tag like [c++], and [regex-golf] simply a language-specific [code-golf]. What's next, [c++-golf]? :-P I'm making this into an explicit synonym request. (+1( \$\endgroup\$
    – Doorknob
    Jan 26, 2014 at 1:01

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