Why people are saying it's best practice? This code is inefficient.

I took a look at the Python translation and found the bug; it's now fixed. Thanks for spotting the issue.

Good kata! One thing seemed wrong to me: (using python)
On December 22, one entrant had an ID that expired on Dec 16 1982, so I denied entry. That was marked as incorrect. Apparently, a document is only expired if its expiration date is November 22 or earlier, regardless of what day it is currently.
It seems strange that the test would go out of its way to change the date with each new bulletin, but not expect the code to increment the date for expired documents.
Does that sound like an issue to anyone else?

well, you should unpublish the kata, don't you think?

That last one's harder than this one, because it includes negatives and decimals.

And another one in beta: https://www.codewars.com/kata/add-commas-to-a-number-1

dang... guess i didn't search hard enough

That works, I guess there's no real reason it shouldn't be allowed.
I ranked it as a 6 because I was picturing it as a kind of beginner recursion practice, but I can see how other solutions could be significantly simpler.

ah, that reminded me of something... x/

Duplicate:
https://www.codewars.com/kata/grouped-by-commas
https://www.codewars.com/kata/converting-integer-to-currency-format

You can't. Unless you want to parse the user's solution to check that it doesn't include this hack. Although, it'll be very hard.

Even if you somehow forbid it, this kata will still end up 7 kyu at most, because the algorithm is fairly simple.

mmmmh, unless you scan the text file of the code, I don't think so. Though, honestly, I don't think that would be a good idea to forbid it for several reasons:

• first of all, there are a lot of ways to call this. It will be very hard to forbid all of them for you, especially with python
• it's rather rarely used, I believe, so good information for the users to see it exists (a good introduction to python idioms, "battery included").

Out of this, this is your kata. But if you go for the restriction, be prepared to see a lot of hacks. ;)

Good point. Is there a way to check whether the user uses that function?