Closing old question as duplicate of a new one

Question

What is our policy regarding closing an old challenge as a duplicate of a new one?

I know this happens on other sites (at least SO), if the newer question is generally better or usually if it gathers better answers (such that the old one acts as a "redirect" to the canonical answer). Now this doesn't really apply here, but today there was a case where I'd be tempted to do just that.

The challenges in questions are:

• Write a word equation solver
• Write a FAST word equation solver

The former is mostly a code-golf question, but with an odd rule regarding how whitespace is counted - which basically made the actual task fairly irrelevant and turned it into "decode a whitespace-encoded program in the least amount of characters".

The latter has exactly the same task as the form, but is a fastest-code challenge. Now Peter Taylor (and apparently four others) was of the opinion that the new one is a duplicate of the old one, since all of the old answers are valid on the new one. For starters, I'd say that's irrelevant if none of them are competitive, but that's not the point of this question here. (I address that over here.)

The more important problem is, that due to the old question's scoring being easy to abuse, any competitive answer to the new one could still be turned into a winning answer for the old one. So now you could indeed craft an answer that works on both of them. But to me, this is just saying that the new challenge is really decent, and the old one has some serious problems, and (since answers can be copied from the new to the old one, but not the other way round) that kinda makes the old one a duplicate of the new one.

So what is the community's opinion on this? Do we close old challenges in favour of better new ones? Or is there a problem with that in some way (like being punishing for the original creator of the challenge concept)? Have there been any precedents?

Edit:

Rainbolt found some support for this on Meta.SE:

• Why is an older question marked as duplicate?
• Should I vote to close a duplicate question, even though it's much newer, and has more up to date answers?

Answer 1

Guidelines for closing duplicates

This is not intended to be an all-or-nothing list, nor is it exhaustive. These are simply questions to ask yourself when considering casting a close-as-dupe vote on a challenge, which may influence your decision.

• Is the "meat" of the challenges the same? This is probably the easiest to determine; casting aside input and output formats (unless they are complex and/or interesting enough to be worthy of a challenge on their own), do the challenges ask users to solve the same problem? If so, then the challenges are almost certainly duplicates.

• Could answers from one be posted to the other, with trivial modifications at most, and be competitive? This answer of Martin's is probably the most-cited answer when it comes to dupe policy. Martin does an excellent job of explaining the criteria he uses, which I also try to use in my judgements. The key point is that the answers would be competitive. It is not enough for the answers to be valid; they must have a serious chance of winning the challenge (or, if not winning, at least performing reasonably well). This is kind of a fuzzy criterion, so I'm going to try to solidify it more: if the answers would get deleted due to not being serious contenders (as per our normal rules), they're not competitive, and the questions are not duplicates by this metric.

• Which challenge is better? We've had a whole lot of discussion on this topic (see Duplicates with different restrictions or no restrictions). Consider which of the challenges has the clearest specification, violates the least number of Things to avoid when writing challenges, and is the most interesting. This is a very subjective decision. It ultimately boils down to, which challenge do you think is best to keep? Be aware that "none of the above" is an acceptable answer if you believe none of the challenges in question meet our quality standards.

If, after considering all of the above, you're still not sure what should be done, start a discussion about the challenges. The community here will either point you towards existing policies/consensus, or we will debate until a consensus is formed.

Important note: As Martin's answer mentioned, closing old challenges as dupes of new challenges should be considered on a post-by-post basis, so a meta discussion is probably appropriate for each. This shouldn't spawn an excessive amount of meta posts, as the number of old challenges this policy would apply to are limited. Discuss before you vote, to avoid confusion! These guidelines are intended to help you decide which course of action you think is best, so you can take the appropriate steps to resolve the issue.

Answer 2

I don't see why either question has to be closed.

1. They are clearly different challenges for the reasons you mention.
2. There may be users that would like to answer the new question that would not have wanted to answer the old question (because of the differences)
3. There may be users that would like to answer the new question that missed the old question. i.e. perhaps they only joined the site within the last month, or were just not online often enough before the question got knocked off the "active/recent questions" list. Are these users expected to go and search for old/inactive questions to answer?
4. What's the benefit to the site for closing duplicates? Or what harm do duplicates cause to this site? I can understand the need to close duplicates on stack overflow. On stack overflow, old questions can still be relevant/useful to users. On this site, the answers are for the benefit of the users answering and not for future users of the site. Answers on here do not have a general purpose but are just for the sake of the challenge.

Answer 3

There have been a handful of cases before where I've wanted to do this. E.g. write a code the find n-th number of Gray Code list (completely pointless winning condition because optimality is trivial) could reasonably have been closed in favour of Traverse all numbers with only one bit flip per step (which Give me the Gray Code list of bit width n should also be closed as a duplicate of, but I digress).

The problem is what to do with the answers on the old question. Closing as a dupe doesn't migrate the answers (which is a good thing!). Duplicating the answers isn't a solution; asking people to copy their answers over and then delete the original isn't a great solution, and they also risk a net loss in rep; and ending up with two different sets of answers and two different accepted answers is not a good solution either. And that's without getting into the effective penalty on answers to the old question that it will be the new question which is getting bumped and attracting new upvotes.

The only way I can see of getting this to work well is if the moderators undertake to move the answers across, if they even have the ability to do that.

So as a general rule I think the solution is to close the new question as a dupe of the old one and improve the old one. The only case where this doesn't answer is where the biggest difference is a change of scoring system.