funny cheat :-)

You could've avoided to_str, to_ary, to_hash check if defined method_missing as self.method_missing. In this case it will be defined for main object only, instead of being defined for Object as a class

But no one wants do do these :'(
This kata has stuck in beta for 200 days

Need more pure number theory kata like this.

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Haskell translation

Indeed. Nice job!

Done, thanks!

( for JS )
In the random tests, you should pass in copies of arr (.slice() is your friend) rather than the arr itself.

Thanks! I've fixed it.