Why is the following question off-topic?

Why is every continuous function on the reals determined by its value on rationals?

  • 7
    $\begingroup$ It's a PSQ: a bare demand for an answer with no context given: no reason for asking, no indication as to why the question might be interesting. The close reasons that reviewers can select from are not particularly nuanced so "off-topic" covers a broad scope. But... why are you asking about a five-year-old closure of a low quality question? $\endgroup$
    – postmortes
    Commented Jul 29, 2021 at 12:19
  • $\begingroup$ I'm asking because this was exactly the question I was going to ask but found that it had already been asked but closed. $\endgroup$
    – sno
    Commented Jul 29, 2021 at 12:20
  • 4
    $\begingroup$ So? There are answers to it, and if you were to ask it again your question would be closed as a duplicate. I guess I don't understand what you want to achieve by asking this question. $\endgroup$
    – postmortes
    Commented Jul 29, 2021 at 12:22
  • 1
    $\begingroup$ I just wanted to understand why it was closed which seemed bizzare to me. $\endgroup$
    – sno
    Commented Jul 29, 2021 at 12:24
  • 5
    $\begingroup$ Ah, then it's because it's very low quality. Please read the Enforcement of Quality Standards thread here on meta if you want to understand more about what we (as a community) expect from questions $\endgroup$
    – postmortes
    Commented Jul 29, 2021 at 12:25
  • $\begingroup$ I want to close this meta question but can't find a good duplicate $\endgroup$
    – user876009
    Commented Jul 29, 2021 at 12:31
  • 7
    $\begingroup$ I will add that this question was probably asked many times. If you look at the question "Can there be two distinct, continuous functions that are equal at all rationals?" there are 22 questions linked to it, most of them closely related. $\endgroup$ Commented Jul 29, 2021 at 12:42

1 Answer 1


It is worth mentioning that close reasons are displayed differently to different users. You should see this: "Closed. This question is off-topic. It is not currently accepting answers."

However, users who can cast close/reopen votes see this:

This question is missing context or other details: Please improve the question by providing additional context, which ideally includes your thoughts on the problem and any attempts you have made to solve it. This information helps others identify where you have difficulties and helps them write answers appropriate to your experience level.

Notice that it contains the link to this post: How to ask a good question. (This link is contained also in the version displayed to the user.)

The more detailed description says that the reason for closure was insufficient context. You can find some related posts here on meta if you browse through the questions tagged .

Several versions of the message were introduced in August 2019, some more details can be found here: How could we improve our planned post notice improvements?


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