Index in the repeat function(Kotlin)

I've been learning Kotlin lately and I came across something I can't understand.

import kotlin.random.Random
  
fun main() {
  var maximumDiscountValue = 0
 
  repeat(3) { index ->
     val discount = Random.nextInt(10)
     println("Attempt ${index+1}: $discount")
     if (discount > maximumDiscountValue) {
        maximumDiscountValue = discount
     }
  }
 
  println(maximumDiscountValue)
}
 
val number = 3
var output = 2
repeat(5) { index ->
  output += (index * number)
}
println(output)

I don't understand what "index" does in there. If someone knows what, I'll be glad to know.

The repeat function specifies a number of times (3 and 5 in your case) a specific lambada function has to be executed. Index is a zero-based number that will be incremented during each execution.

In your first repeat

repeat(5) {
 ... your index will be 0, 1, 2, 3 and 4
}

Here the source code of the repeat function

@kotlin.internal.InlineOnly
public inline fun repeat(times: Int, action: (Int) -> Unit) {
    contract { callsInPlace(action) }

    for (index in 0 until times) {
        action(index)
    }
}