aw, thank you! Really nice of you to take the time to leave a comment :)

Eh I think in that case better to take it down completely-- without the option of reading about the solution it seems to me this would be more frustrating than fun for most users. Thanks for the feedback.

Ok so basically if you try to implement the first versions of the formulas given in the article they should work, not the versions after algebraic manipulation which are not saying quite what they look like. But I'm starting to think this is not going to be a fun kata for people, so I suspect I should just take it down.

I feel you on this. I wasn't sure whether to make this into a kata at all, because the interesting part is the maths rather than the programming, I just think it's a really delightful concept and an excellent brain-teaser so I wanted to share it. But I agree that to the extent that people just go to the link and implement the functions there it's not a novel coding challenge. Is there anything I could change that would make you happier with this kata, or is your view that it should just be taken down completely?

yes that looks right to me, is your solution not going through? May well be a problem in my implementation

I have no idea how to rank it honestly. If you click the link to the paper (in the problem description) and just implement the solution it's pretty easy; if you try to derive it yourself it's incredibly hard. Or did you click the link and still think it's too hard?

forgive me if I've missed something but:

1. I think the description should mention the name of the table
2. I think the description should mention that we're expected to return 3 columns and not-return the original "id" column

I think the note in the description is not very clear -- it should say "return user_id as varchar", not "assume that user_id will have type varchar" which is about the input, not the output

Thanks barakplasma, looks great all round -- thanks for taking the time to od the test cases and sample cases right! approved

I also get annoyed when people in the comments write "my code didn't pass therefore your tests are broken" when a whole lot of people have already passed the kata, but in this case I was saying that a bad solution also passed which is perfectly consistent with a whole lot of people passing the kata properly

i'm editing the description now, what kind of example would you give without spoiling the challenge?

hi there -- i'm editing the description now, let me know your suggestions

Ok I've edited the description to remove "unique" and to clarify "United States of America".

I don't know how to change the column name without causing more trouble.

What kind of example would you give without spoiling the challenge?

hmmm yes I see you're totally right -- I think I'm going to take this kata down, it doesn't make sense as currently written.

sorry, very dumb mistake on my end -- can you try again now?