kotlin-stdlib/kotlin.collections/runningReduceIndexed

runningReduceIndexed

inline fun <S, T : S> Array<out T>.runningReduceIndexed(operation: (index: Int, acc: S, T) -> S): List<S>(source)
@ExperimentalUnsignedTypes
inline fun UIntArray.runningReduceIndexed(operation: (index: Int, acc: UInt, UInt) -> UInt): List<UInt>(source)
@ExperimentalUnsignedTypes
inline fun ULongArray.runningReduceIndexed(operation: (index: Int, acc: ULong, ULong) -> ULong): List<ULong>(source)
@ExperimentalUnsignedTypes
inline fun UByteArray.runningReduceIndexed(operation: (index: Int, acc: UByte, UByte) -> UByte): List<UByte>(source)
@ExperimentalUnsignedTypes
inline fun UShortArray.runningReduceIndexed(operation: (index: Int, acc: UShort, UShort) -> UShort): List<UShort>(source)

Returns a list containing successive accumulation values generated by applying operation from left to right to each element, its index in the original array and current accumulator value that starts with the first element of this array.

Note that acc value passed to operation function should not be mutated; otherwise it would affect the previous value in resulting list.

Since Kotlin

1.4

Parameters

operation

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

Samples

import kotlin.test.*

fun main() { 
   //sampleStart 
   val strings = listOf("a", "b", "c", "d")
println(strings.runningReduce { acc, string -> acc + string }) // [a, ab, abc, abcd]
println(strings.runningReduceIndexed { index, acc, string -> acc + string + index }) // [a, ab1, ab1c2, ab1c2d3]

println(emptyList<String>().runningReduce { _, _ -> "X" }) // [] 
   //sampleEnd
}
inline fun ByteArray.runningReduceIndexed(operation: (index: Int, acc: Byte, Byte) -> Byte): List<Byte>(source)
inline fun ShortArray.runningReduceIndexed(operation: (index: Int, acc: Short, Short) -> Short): List<Short>(source)
inline fun IntArray.runningReduceIndexed(operation: (index: Int, acc: Int, Int) -> Int): List<Int>(source)
inline fun LongArray.runningReduceIndexed(operation: (index: Int, acc: Long, Long) -> Long): List<Long>(source)
inline fun FloatArray.runningReduceIndexed(operation: (index: Int, acc: Float, Float) -> Float): List<Float>(source)
inline fun DoubleArray.runningReduceIndexed(operation: (index: Int, acc: Double, Double) -> Double): List<Double>(source)
inline fun BooleanArray.runningReduceIndexed(operation: (index: Int, acc: Boolean, Boolean) -> Boolean): List<Boolean>(source)
inline fun CharArray.runningReduceIndexed(operation: (index: Int, acc: Char, Char) -> Char): List<Char>(source)

Returns a list containing successive accumulation values generated by applying operation from left to right to each element, its index in the original array and current accumulator value that starts with the first element of this array.

Since Kotlin

1.4

Parameters

operation

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

Samples

import kotlin.test.*

fun main() { 
   //sampleStart 
   val strings = listOf("a", "b", "c", "d")
println(strings.runningReduce { acc, string -> acc + string }) // [a, ab, abc, abcd]
println(strings.runningReduceIndexed { index, acc, string -> acc + string + index }) // [a, ab1, ab1c2, ab1c2d3]

println(emptyList<String>().runningReduce { _, _ -> "X" }) // [] 
   //sampleEnd
}
inline fun <S, T : S> Iterable<T>.runningReduceIndexed(operation: (index: Int, acc: S, T) -> S): List<S>(source)

Returns a list containing successive accumulation values generated by applying operation from left to right to each element, its index in the original collection and current accumulator value that starts with the first element of this collection.

Note that acc value passed to operation function should not be mutated; otherwise it would affect the previous value in resulting list.

Since Kotlin

1.4

Parameters

operation

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

Samples

import kotlin.test.*

fun main() { 
   //sampleStart 
   val strings = listOf("a", "b", "c", "d")
println(strings.runningReduce { acc, string -> acc + string }) // [a, ab, abc, abcd]
println(strings.runningReduceIndexed { index, acc, string -> acc + string + index }) // [a, ab1, ab1c2, ab1c2d3]

println(emptyList<String>().runningReduce { _, _ -> "X" }) // [] 
   //sampleEnd
}