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There's any problem with reverseArray because copiler write that: Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 6
	at my.demo.AppKt.invertivett(App.kt:58)
	at my.demo.AppKt.main(App.kt:47)

Why do you need own reverseArray function if stdlib has  .reverse() extension

i didn't know that function :slightly_smiling_face:
But, now i'm doing all the code without exstension to learn sintax and languages...
Another question, where can i find kotlin's extensions?

&gt; without exstension to learn sintax and languages
Isn’t stdlib functions is part of language and syntax?

&gt;  i find kotlin’s extensions?
What do you mean? Extension function is just a language feature:
<https://kotlinlang.org/docs/reference/extensions.html>

Standard library contains a lot of them, just check reference.
For example this is doc for package `kotlin.collections` which contains a lot of extensions for different types, including `Array.reverse()`:
<https://kotlinlang.org/api/latest/jvm/stdlib/kotlin.collections/index.html>

also instead of `printArray` or `printStringArray` you can just use array extension `*Array.contentToString()`

I think trying to reimplement all those function is not very efficient way, because instead using very practical and useful standard library to solve some tasks (even tasks just for education or samples) you spending time on implementing what already is part of the language (which also mean that you are not learning stdlib which especially important when you work on some real task in future)

<@UMW0W4ZL7> Anyway, I also checked your `reverseArray` implementation and it’s expected that it’s not working, you use `for` loop in a wrong way. Not clearly sure what you try to achieve, you probably need range, because your code just iterate array with index and `var nMiddle` just not used (because one in for loop doesn’t override it). And use `withIndex` is not very efficcient way to work with arrays, it creates a lot of overhead (one additional object on every item) for case which can be easily solved without it

But maybe you just need range, or something like this:
```for (i in (0..nMiddle))```