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And doesn't work for Integer.MIN_INTEGER? No thanks

Where can I see how many tests pass?

I found out that the Ruby version shows how many tests passed and the Elixir one does not.

C++ is generally much faster than Ruby, but it provides less syntactic sugar, less built-in facilities... In many katas an algorithm working in a language won't work with another. Think about an assembly language like NASM, where the simplest algorithm rated 7 kyu may be harder than 4 kyu in most others. What should be done? It's impossible to reach fairness between languages, they are so different.

No indication is given on how to distinguish tail from loop.