I'm thinking in particular of this very recent question, where the OP has constructed a For loop that actually solves their problem, except that instead of using AppendTo, they are using Append, and so of course they are falling victim to a common new user pitfall.

I am tempted, of course, to vote to close the question (and last I looked, there were already 4), not only because if it being clearly a duplicate: if someone comes to the site looking for the answers posted below the question (because they are working on the same problem), they will not actually end up running into this question, since the title is about For loops, and the question body is about "What went wrong?", not "How do I make this particular algorithm speedier?"

However, I don't want it to close, because there are three excellent (for varying reasons) answers that I would like not to disappear. For instance, Verbeia posted a nice non-speedy answer that exposes the OP to Outer, which every Mathematica user should know and love in their hearts. Belisarius posted a very neat and succinct answer that I find extremely clever and would like to learn from. And finally, any time you can get ciao/rasher to chime in with some performance-tuning, there just has to be something interesting about the question.

I am considering asking the OP to modify the title and question with more details about the actual problem, and have them turn the problem into a performance-tuning question, but I don't know if that's really the right way to go, and I don't know the OP cares enough about the philosophy of the site to put in that work. But I might try anyway, and if the question becomes closed, I'll vote to re-open.

In any case, I am soliciting advice here. This isn't an entirely uncommon problem, but it pops up now and then, and it's been percolating around in my brain for awhile.

  • 1
    "However, I don't want it to close, because there are three excellent (for varying reasons) answers that I would like not to disappear." <-- I just wanted to know that if the question gets closed, the answers will not disappear. It won't be possible to write more answers, but the existing ones won't disappear. Also questions closed as duplicate don't typically get deleted, this one certainly won't.
    – Szabolcs
    Oct 1, 2015 at 17:52
  • @Szabolcs. Yeah I wasn't too sure about this, so that's good to know. Nonetheless, it'd be nice if future questioners could find those answers, even if they answer a pretty localized question.
    – march
    Oct 1, 2015 at 17:57
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    As one of the answerers, my preference would be to edit the question, which any of us can do. The OP has the straightforward answer to his immediate problem already, so there is nothing wrong with us refining the question to make it more findable and more valuable to future visitors. I can't help it, my favourite questions are the beginner questions I can use to teach people how to use Mathematica more effectively.
    – Verbeia
    Oct 1, 2015 at 22:47
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    Agree w/ @Verbeia: I'd like to see the OP perhaps change the title (assuming "way's to do this thing" matters to them) - it's actually a subtly hard problem at the core. I found that part interesting myself. Kind of wish the OP would also elucidate on the details, there are some neat ways to do this super-quickly if the properties of the "typical" example they have hold...
    – ciao
    Oct 3, 2015 at 0:43

1 Answer 1


There is no good reason to close a question just because the OP has made a beginner's mistake, but I think we are doing just that way too much. A question with good answers, even though it is about a beginner's problem, can have much future value to other beginners who come to this site.

My position is: when the question has a positive up-vote score and at least one answer has a positive up-vote score, the question should remain open. Editing the question to make it more likely to turn up in a reasonably worded search is a good idea.

At least, I think we should not be too quick to close. I think we should refrain for a day or two to give time for those who want to answer to write and post their answers. A good answer can take some time to write.

I feel strongly about this because I've been on both sides: I've voted to close too quickly, and I've had questions closed on me before I could get my answer posted. I am now trying hard to refrain from voting to close a recently posted question.

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    I think the idea of refraining for a day or two before voting to close is a good idea, and I've definitely been trigger-happy sometimes, so I will adopt that behavior from now on, I think.
    – march
    Oct 2, 2015 at 3:50
  • I agree with this. I am beginning to think that we are a bit harsh on new users who have missed something that's documented. Mathematica's documentation is huge.
    – Verbeia
    Oct 8, 2015 at 5:05
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    It's often easier to find a solution in the documentation than on this site, yet we still close duplicates. For me, it's not so much how easy it is to find, but whether the answer is there. -- Also, it would be sad if those who are experts in both some field and Mathematica found the site less and less worth their participation. -- Maybe a newbie tag would help...
    – Michael E2
    Oct 8, 2015 at 11:14

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