well, from the docs (https://kotlinlang.org/docs/native-objc-interop.html#initializers) ..

because Kotlin has no concept of extension constructors.

so what is this kata about

ive never heard a good programmer say "so what" before

So what? Python 2 is cool)))

do you mean this is very good way to do this task ?

Yes. If you are sure in your solution and it times out - try a few more times (my solution passed time out on a fifth attempt).

Same here. Has anyone solved this in Kotlin recently? Just to make sure it's not broken.

Fixed.

I finished the kata in c#. It was easy as function for operArray was provided ("Func<long, long, long> fct"). I'm learning kotlin and i just don't understand what i supposedly should to do with operArray "function" argument. Should i create it by myself? Is LongBinaryOperator a function? Any suggestion whould be really greatfull. What does it mean // complete the "..." with your generic function ?

There are many other "tricky kotlin" Katas, you should do all of them!

It took me a bit of time to figure this one out, but man you can do some really insane stuff in Kotlin!

Indeed, a very satisfying kata when completed ! I'm new to Kotlin, it's so powerful.
If that may help anyone, it took me about 5 minutes of googling to get a slight hint, and I tried a bit, and... voilà

Yes, because a very little hint will become spoiler of doing this.

Learning resources? Maybe Kotlin's language reference. Make use of your imagination!
You won't find anything called "extension constructor" that you can find explicitly in any Kotlin tutorials, otherwise this will become a 8kyu.

There's no actual real-life usages of tricks like this, for code readability and maintainability.

I agree, and additionally, the wording of the kata is so unclear that if I didn't already know what reduce does, I would have had no idea what the problem is actually supposed to be.

By the way, there're more than 3 ways of doing this.

You don't know Kotlin. There's some tricks to make the unchanged tests pass.