Ok, I was just learning erlang sintax.. Do you like my new solutions?

Ok, thanks. Well, in my understanding (I'd appreciate you to correct me if I'm wrong), stack overflow may happen in case there is a great amount of recursions (depending on the language). Here, given the max value for an u64, there cannot be more than 20 recursions, so no way to get SO... Or am I wrong?

I dont't know what it is (I've just searched for it, and I can't figure it out...), and how this is related my solution. You'd be kind to tell me more :)

I don't understand what my code fails

That's not a kata issue. There's over 900 haskell completions. The code you posted clearly has syntax errors, and probably some logical ones too.