reduceIndexedOrNull
Accumulates value starting with the first character and applying operation from left to right to current accumulator value and each character with its index in the original char sequence.
inline fun CharSequence.reduceIndexedOrNull(operation: (index: Int, acc: Char, Char) -> Char): Char?(source)
fun main() {
val text = "kotlin"
val result = text.reduceIndexedOrNull { index, acc, current ->
// Keep the accumulator for even indices, otherwise take the current character
if (index % 2 == 0) acc else current
}
println(result) // prints: n
val empty = "".reduceIndexedOrNull { _, _, _ -> 'X' }
println(empty) // prints: null
}