inline fun <S, T : S> Array<out T>.reduceRightIndexed(
    operation: (index: Int, T, acc: S) -> S
): S

inline fun ByteArray.reduceRightIndexed(
    operation: (index: Int, Byte, acc: Byte) -> Byte
): Byte

inline fun ShortArray.reduceRightIndexed(
    operation: (index: Int, Short, acc: Short) -> Short
): Short

inline fun IntArray.reduceRightIndexed(
    operation: (index: Int, Int, acc: Int) -> Int
): Int

inline fun LongArray.reduceRightIndexed(
    operation: (index: Int, Long, acc: Long) -> Long
): Long

inline fun FloatArray.reduceRightIndexed(
    operation: (index: Int, Float, acc: Float) -> Float
): Float

inline fun DoubleArray.reduceRightIndexed(
    operation: (index: Int, Double, acc: Double) -> Double
): Double

inline fun BooleanArray.reduceRightIndexed(
    operation: (index: Int, Boolean, acc: Boolean) -> Boolean
): Boolean

inline fun CharArray.reduceRightIndexed(
    operation: (index: Int, Char, acc: Char) -> Char
): Char

@ExperimentalUnsignedTypes inline fun UIntArray.reduceRightIndexed(
    operation: (index: Int, UInt, acc: UInt) -> UInt
): UInt

@ExperimentalUnsignedTypes inline fun ULongArray.reduceRightIndexed(
    operation: (index: Int, ULong, acc: ULong) -> ULong
): ULong

@ExperimentalUnsignedTypes inline fun UByteArray.reduceRightIndexed(
    operation: (index: Int, UByte, acc: UByte) -> UByte
): UByte

@ExperimentalUnsignedTypes inline fun UShortArray.reduceRightIndexed(
    operation: (index: Int, UShort, acc: UShort) -> UShort
): UShort

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.

Throws an exception if this array is empty. If the array can be empty in an expected way, please use reduceRightIndexedOrNull instead. It returns null when its receiver is empty.

import kotlin.test.*

fun main(args: Array<String>) {
//sampleStart
val strings = listOf("a", "b", "c", "d")
println(strings.reduceRight { string, acc -> acc + string }) // dcba
println(strings.reduceRightIndexed { index, string, acc -> acc + string + index }) // dc2b1a0

// emptyList<Int>().reduceRight { _, _ -> 0 } //  will fail
//sampleEnd
}

Parameters

operation - function that takes the index of an element, the element itself and current accumulator value, and calculates the next accumulator value.

inline fun <S, T : S> List<T>.reduceRightIndexed(
    operation: (index: Int, T, acc: S) -> S
): S

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.

Throws an exception if this list is empty. If the list can be empty in an expected way, please use reduceRightIndexedOrNull instead. It returns null when its receiver is empty.

import kotlin.test.*

fun main(args: Array<String>) {
//sampleStart
val strings = listOf("a", "b", "c", "d")
println(strings.reduceRight { string, acc -> acc + string }) // dcba
println(strings.reduceRightIndexed { index, string, acc -> acc + string + index }) // dc2b1a0

// emptyList<Int>().reduceRight { _, _ -> 0 } //  will fail
//sampleEnd
}

Parameters

operation - function that takes the index of an element, the element itself and current accumulator value, and calculates the next accumulator value.