I recently found this question:

If there is comparison between two variables then language is not regular. Then how the below two languages L1 and L2 Regular? Please Explain

It is closed as a duplicate of our reference question for regular languages. However, in my (and Apass.Jack's) opinion, it is not a duplicate. Basically, the solution includes two parts:

  1. Show the language is equivalent to $\{a^t\mid t\ge 1\}$ (or $\ge 2$, whatever).

  2. Show $\{a^t\mid t\ge 1\}$ is regular.

Obviously, Part 1 is the (relatively) tricky part (we can see in the comment that OP is indeed confused with this part), while our reference question only deals with Part 2.

Of course, this question itself may not be a good question. First, it may be too simple, and second, the OP shows no effort. However, neither should be a close reason:

We can downvote this question because of these issues, but I don't see any reason to close it.

So should this question really be closed?

BTW, this question has ever been voted to reopen, but only one other user agrees with me.


2 Answers 2


Tl;dr: I stand by my comment there: the question is a problem dump.

We have long since been distinguishing between "asks a comprehensible question but didn't include own effort" (--> comment, downvote) and "copy-paste of exercise problem, no own question" (--> close as unclear). While it can be argued that this one falls in the border area (we get a hint on the OP's tought process: "If there is comparison between two variables then language is not regular") I still think it was reasonable to close (2 regular users + 1 mod, then).

I note that the OP did not make any effort to improve their question, nor did anybody else. Instead, the OP attempted to enter a coaching session in the comments, which is not a good use of the platform.

I currently do not see a reason to re-open. If you think there is a meaningful question there (item 1 in your proposed interpretation, maybe?) that is not covered by the reference questions, please edit the question into shape and then flag for reopening.

  • 2
    $\begingroup$ "Instead, the OP attempted to enter a coaching session in the comments, which is not a good use of the platform." I think that is debatable, but I also think the more important point is that if the OP has extensive conversation in the comments (regarding clarity/lack of work of the question), then it seems there is no reason to give an answer (rather than hints in the comments), and therefore no reason to reopen. $\endgroup$
    – Discrete lizard Mod
    Commented Mar 6, 2019 at 8:31
  • $\begingroup$ Reasonable, but how can we tell if a question is a copy-paste of an exercise problem? $\endgroup$
    – xskxzr
    Commented Mar 6, 2019 at 9:20
  • $\begingroup$ @xskxzr There is no perfect decision method, of course. I have seen hundreds and created dozens of exercise sheets; does the phrasing remind me of those? (imperatives, clear scope, clean notation, no application context, etc...) Is any form of I-message ("I tried...", "I don't understand...", ...) missing? Sometimes, people even post screenshots. $\endgroup$
    – Raphael
    Commented Mar 6, 2019 at 10:21
  • $\begingroup$ That said, the canned comments specifically (try to) avoid any form of judgement or formulation that may be perceived as name-calling, instead focusing on explaining why the post at hand is bad. $\endgroup$
    – Raphael
    Commented Mar 6, 2019 at 10:23
  • $\begingroup$ But isn't it unfair to close a question just because it looks like an exercise problem? I found your another post that also does not suggest closing homework questions. $\endgroup$
    – xskxzr
    Commented Mar 6, 2019 at 14:08
  • 1
    $\begingroup$ @xskxzr And if you read carefully, you'll find that the point is not to close homework questions, but poor questions. But you asked me specifically how to detect exercise problems, so that's what I answered. $\endgroup$
    – Raphael
    Commented Mar 6, 2019 at 17:16
  • $\begingroup$ I noticed the OP of that question gives an example "are the following languages are regular for ...", of course a homework dump. You also said "However, our homework policy mandates us to endure and deal with them, mostly because we can not reliably tell lazy homework-dumper from inexperienced self-learner". So I read that answer as a guide to how to deal with homework dump. $\endgroup$
    – xskxzr
    Commented Mar 7, 2019 at 3:51

I am still not convinced about the question after edit being proper. When I cast vote it looked like problem dump and dupe. Only after comments it become obvious that OP had some unvocalized problem in mind.

After edit I have left a comment with proposal to state parts that that differ this from duplicate, but without further response. Now I see it is not exactly dupe and effort was put to it, but we have come to consensus that comment based coaching with question changing is not good to us.

With a bit follow up (putting underlaying question to body of the post) I will gladly cast reopen vote.

I have expected one more edit (to gather comments and state fully fledged post) and reopen from queue, but it didn't get that far.

Effort is orthogonal to problem: it looks like dupe, after edit it is not fully articulated question and somehow momentum was lost. Now lack of interest mildly suggests dump.

I strongly dislike improvements against OP's will, as it results in reccuring pop up at main page by Community bot.

In my opinion the best option now is to create self-answered question instead of mangling old one, because I am against comment-based changes to question.


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