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kotlinlang

```
fun tests(start: Int, end: Int): IntArray =
 (start until end).toList().toIntArray()
```

thanks, so I have to convert it to a `List` first and then `Array`? Isn't that expensive?

Ye, it's how Kotlin collections work unfortunately. In `Scala` they have a special system with implicit classes which makes it more flexible. 

`toArray` is defined on `Collection` so only way to do it without writing any custom code is this. If you are worried about performance I would definitely write a custom extension method on `IntRange` to convert `toIntArray` directly.