A simple lookup of "concatenation" reveals 1,637 questions with that word in the post. Thus it is not uncommon on MSE with questions based around that topic.


Here are some suggestions. Below each question I have added some ideas as to the pros and cons of them.

  1. Should the tag be added to the list of tags on MSE?

    • Based on the existing tags, I don't think there is one that covers concatenation. The closest one to that I can think of is , but I think it is more common to mention the former than the latter (this opinion may be debatable). After all, the latter tag only has 820 questions.

    • Concatenation can also be with regards to strings and languages. The topics of and come into mind here. Therefore in this aspect, there is not really a similar tag for it, at least from what I have searched.

  2. If in favour of creating said tag, should it be further subdivided into tags such as and ?

    • The reason I suggest this follow-up question is that many of the questions that arise from the search query fall under the categories of either the concatenation of integers/primes/palindromes etc. or the concatenation of characters/languages etc.

    • However, there are some questions that are in neither category, so creating a different tag under the branch of concatenation each time would be excessive. I believe this would be the major drawback.

What does the community think?

  • 4
    $\begingroup$ I don't see the tag "concatenation" as a useful tag. It just does not convey much in my opinion. It seems like it would be yet another tag of which no-one knows what is actually the intent. You address this in a way when you propose further refinements. But there is really no point in creating the 'umbrella' tag. Mostly we try to get rid of those. Maybe concatenation-of-numbers could be useful. Not sure about the strings. $\endgroup$ – quid May 26 '19 at 13:16
  • $\begingroup$ @quid I'm in support of a more specific tag (and its definition when it comes to its creation) so I agree that concatenation by itself is quite broad. Perhaps we can just have the two tags for numbers and strings and leave the other questions as they are. $\endgroup$ – TheSimpliFire May 26 '19 at 13:23
  • 2
    $\begingroup$ I am not convinced that concatenation of strings is a useful tag. What would that be good for? If there should be a tag for operations with strings, alright, but to focus on concatenation (a rather straightforward operation) I don't see that being interesting as a tag. $\endgroup$ – quid May 26 '19 at 13:27
  • $\begingroup$ Actually, I think a tag for such an operation for strings/languages would be useful, as for languages in particular, arXiv has quite a number of articles on the topic, as well as the abundancy of these questions on MSE relative to those for number concatenation. Unfortunately, my expertise is not in this area, so I will have to leave it to those with a good background on this to decide. $\endgroup$ – TheSimpliFire May 26 '19 at 13:34
  • 4
    $\begingroup$ We do have a tag for formal-languages. $\endgroup$ – quid May 26 '19 at 13:43
  • $\begingroup$ Indeed. That would settle the problem. I'm surprised I missed that one. $\endgroup$ – TheSimpliFire May 26 '19 at 13:47


  • If they want to talk about truncatable primes or russian doll primes, we have the prime numbers tag.

  • Number of such concatenations, combinatorics.

  • Use in code: programming, or computer algebra systems (or computer science stack exchange).

They are already separated by type, in the tags used ( questionable if correctly however).


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