reduceRightIndexedOrNull
inline fun <S, T : S> Array<out T>.reduceRightIndexedOrNull(
operation: (index: Int, T, acc: S) -> S
): S?
(source)
inline fun ShortArray.reduceRightIndexedOrNull(
operation: (index: Int, Short, acc: Short) -> Short
): Short?
(source)
inline fun FloatArray.reduceRightIndexedOrNull(
operation: (index: Int, Float, acc: Float) -> Float
): Float?
(source)
inline fun DoubleArray.reduceRightIndexedOrNull(
operation: (index: Int, Double, acc: Double) -> Double
): Double?
(source)
inline fun BooleanArray.reduceRightIndexedOrNull(
operation: (index: Int, Boolean, acc: Boolean) -> Boolean
): Boolean?
(source)
Accumulates value starting with the last element and applying operation from right to left to each element with its index in the original array and current accumulator value.
Returns null
if the array is empty.
import kotlin.test.*
fun main(args: Array<String>) {
//sampleStart
val strings = listOf("a", "b", "c", "d")
println(strings.reduceRightOrNull { string, acc -> acc + string }) // dcba
println(strings.reduceRightIndexedOrNull { index, string, acc -> acc + string + index }) // dc2b1a0
println(emptyList<String>().reduceRightOrNull { _, _ -> "" }) // null
//sampleEnd
}
Parameters
operation
- function that takes the index of an element, the element itself and current accumulator value,
and calculates the next accumulator value.
Accumulates value starting with the last element and applying operation from right to left to each element with its index in the original list and current accumulator value.
Returns null
if the list is empty.
import kotlin.test.*
fun main(args: Array<String>) {
//sampleStart
val strings = listOf("a", "b", "c", "d")
println(strings.reduceRightOrNull { string, acc -> acc + string }) // dcba
println(strings.reduceRightIndexedOrNull { index, string, acc -> acc + string + index }) // dc2b1a0
println(emptyList<String>().reduceRightOrNull { _, _ -> "" }) // null
//sampleEnd
}
Parameters
operation
- function that takes the index of an element, the element itself and current accumulator value,
and calculates the next accumulator value.