kotlin-stdlib/kotlin.collections/reduceRightOrNull

reduceRightOrNull

inline fun <S, T : S> Array<out T>.reduceRightOrNull(operation: (T, S) -> S): S?
Content copied to clipboard
inline fun ByteArray.reduceRightOrNull(operation: (Byte, acc: Byte) -> Byte): Byte?
Content copied to clipboard
inline fun ShortArray.reduceRightOrNull(operation: (Short, acc: Short) -> Short): Short?
Content copied to clipboard
inline fun IntArray.reduceRightOrNull(operation: (Int, acc: Int) -> Int): Int?
Content copied to clipboard
inline fun LongArray.reduceRightOrNull(operation: (Long, acc: Long) -> Long): Long?
Content copied to clipboard
inline fun FloatArray.reduceRightOrNull(operation: (Float, acc: Float) -> Float): Float?
Content copied to clipboard
inline fun DoubleArray.reduceRightOrNull(operation: (Double, acc: Double) -> Double): Double?
Content copied to clipboard
inline fun BooleanArray.reduceRightOrNull(operation: (Boolean, acc: Boolean) -> Boolean): Boolean?
Content copied to clipboard
inline fun CharArray.reduceRightOrNull(operation: (Char, acc: Char) -> Char): Char?
Content copied to clipboard
@ExperimentalUnsignedTypes
inline fun UIntArray.reduceRightOrNull(operation: (UInt, acc: UInt) -> UInt): UInt?
Content copied to clipboard
@ExperimentalUnsignedTypes
inline fun ULongArray.reduceRightOrNull(operation: (ULong, acc: ULong) -> ULong): ULong?
Content copied to clipboard
@ExperimentalUnsignedTypes
inline fun UByteArray.reduceRightOrNull(operation: (UByte, acc: UByte) -> UByte): UByte?
Content copied to clipboard
@ExperimentalUnsignedTypes
inline fun UShortArray.reduceRightOrNull(operation: (UShort, acc: UShort) -> UShort): UShort?
Content copied to clipboard

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

Returns null if the array is empty.

Since Kotlin

1.4

Samples

import samples.*
import kotlin.test.*
fun main() { 
   //sampleStart 
   val strings = listOf("a", "b", "c", "d")
assertPrints(strings.reduceRightOrNull { string, acc -> acc + string }, "dcba")
assertPrints(strings.reduceRightIndexedOrNull { index, string, acc -> acc + string + index }, "dc2b1a0")

assertPrints(emptyList<String>().reduceRightOrNull { _, _ -> "" }, "null") 
   //sampleEnd
}

Parameters

operation

function that takes an element and current accumulator value, and calculates the next accumulator value.


inline fun <S, T : S> List<T>.reduceRightOrNull(operation: (T, S) -> S): S?
Content copied to clipboard

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

Returns null if the list is empty.

Since Kotlin

1.4

Samples

import samples.*
import kotlin.test.*
fun main() { 
   //sampleStart 
   val strings = listOf("a", "b", "c", "d")
assertPrints(strings.reduceRightOrNull { string, acc -> acc + string }, "dcba")
assertPrints(strings.reduceRightIndexedOrNull { index, string, acc -> acc + string + index }, "dc2b1a0")

assertPrints(emptyList<String>().reduceRightOrNull { _, _ -> "" }, "null") 
   //sampleEnd
}

Parameters

operation

function that takes an element and current accumulator value, and calculates the next accumulator value.