That's some trolling indeed

Smart way to do recursive function in R, thanks a lot.

It's a great feature of R ;)

Love the check for zero using conversion to logical!

Yeah that's very confusing.

beautiful work

Why do people for this as best practice?

You can already see that in the example in the description.

The description needs to address how to handle 0, that knowledge is obviously required to pass the tests.

Oh well.

You're right, but the kata description explicitly says "It is guaranteed that a and b are both present in arr", so for this specific task this does the trick.

If a or b does not exist in the arr, we can't do - on nil.
This is a clever solution, but does not deal with edge cases.

Thanks a lot!
That solved my issue.

bad test design, but bad practice on your side too: you're modifying the input arrays. => make copies of them

python: the user can modify the inputs (see just below / I guess it will be the same in other languages)