kotlin-stdlib / kotlin.collections / reduceRight

reduceRight

Common
JVM
JS
Native
1.0
inline fun <S, T : S> Array<out T>.reduceRight(
    operation: (T, acc: S) -> S
): S
(source)
inline fun ByteArray.reduceRight(
    operation: (Byte, acc: Byte) -> Byte
): Byte
(source)
inline fun ShortArray.reduceRight(
    operation: (Short, acc: Short) -> Short
): Short
(source)
inline fun IntArray.reduceRight(
    operation: (Int, acc: Int) -> Int
): Int
(source)
inline fun LongArray.reduceRight(
    operation: (Long, acc: Long) -> Long
): Long
(source)
inline fun FloatArray.reduceRight(
    operation: (Float, acc: Float) -> Float
): Float
(source)
inline fun DoubleArray.reduceRight(
    operation: (Double, acc: Double) -> Double
): Double
(source)
inline fun BooleanArray.reduceRight(
    operation: (Boolean, acc: Boolean) -> Boolean
): Boolean
(source)
inline fun CharArray.reduceRight(
    operation: (Char, acc: Char) -> Char
): Char
(source)
@ExperimentalUnsignedTypes inline fun UIntArray.reduceRight(
    operation: (UInt, acc: UInt) -> UInt
): UInt
(source)
@ExperimentalUnsignedTypes inline fun ULongArray.reduceRight(
    operation: (ULong, acc: ULong) -> ULong
): ULong
(source)
@ExperimentalUnsignedTypes inline fun UByteArray.reduceRight(
    operation: (UByte, acc: UByte) -> UByte
): UByte
(source)
@ExperimentalUnsignedTypes inline fun UShortArray.reduceRight(
    operation: (UShort, acc: UShort) -> UShort
): UShort
(source)

Accumulates value starting with the last element and applying operation from right to left to each element and current accumulator value.

Throws an exception if this array is empty. If the array can be empty in an expected way, please use reduceRightOrNull 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 an element and current accumulator value, and calculates the next accumulator value.

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

Accumulates value starting with the last element and applying operation from right to left to each element and current accumulator value.

Throws an exception if this list is empty. If the list can be empty in an expected way, please use reduceRightOrNull 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 an element and current accumulator value, and calculates the next accumulator value.