Approved

Lua translation and Prolog translation

Fixed.

Self-approved :)

Added random tests to CoffeeScript

Double every other digit, scanning from right to left, starting from the second digit (from the right).

Whilst your code is doubling every digit.

Your solution is wrong and fails with inputs like 8675309 it returns true instead of false.

8675309 ==> [8, 6*, 7, 5*, 3, 0*, 9] ==> [8, 12, 7, 10, 3, 0, 9] ==> [8, 3, 7, 1, 3, 0, 9]
[8, 3, 7, 1, 3, 0, 9] ==> [8, 3, 7, 1, 3, 0, 9] = 31
31 (modulus) 10 ==> 1 , which is not equal to 0, so this is not a valid credit card number

Not a kata issue.

If a resulting number is greater than 9, replace it with the sum of its own digits (which is the same as subtracting 9 from it)

You're not doing that right.

Everything is working on my end, and I am passing the test. But when I attempt, it is saying expected true to equal false and vice versa if I change.

Scala translation

Good problem!

Nice, thanks for that @hobovsky. Indeed, it's passing now.

I changed the reference solution which seemed to be buggy, and your solution passes now. Please verify and mark the issue as resolved if the problem does not occur anymore.

Should be fixed.

Could you check again?

The F# random test is wrong apparently. My code passes all the manual tests, but fails on the random. I added a printfn instruction to show what is the input and it's a big quantity of numbers.