kotlin-stdlib / kotlin.collections / reduceRightIndexed

reduceRightIndexed

Common
JVM
JS
Native
1.0
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 last element and applying operation from right to left to each element with its index in the original array and current accumulator value.

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.

Common
JVM
JS
Native
1.0
inline fun <S, T : S> List<T>.reduceRightIndexed(
    operation: (index: Int, T, acc: S) -> S
): S

Accumulates value starting with last element and applying operation from right to left to each element with its index in the original list and current accumulator value.

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.