kotlin for loop i++ is not possible code example

Example 1: for loop kotlin

val array = arrayOf(1, 3, 9)
for (item in array) {
    //loops items
}
for (index in 0..array.size - 1) {
	//loops all indices
}
for (index in 0 untill array.size) {
    //loops all indices
}
for (index in array.indices) {
    //loops all indices (performs just as well as two examples above)
}

Example 2: Kotlin when

val x = 3
when(x) {
    3 -> println("yes")
    8 -> println("no")
    else -> println("maybe")
}
// when can also be used as an expression!
val y = when(x) {
    3 -> "yes"
    8 -> "no"
    else -> "maybe"
}
println(y) // "yes"