runningReduce

inline fun CharSequence.runningReduce(operation: (acc: Char, Char) -> Char): List<Char>

Returns a list containing successive accumulation values generated by applying operation from left to right to each character and current accumulator value that starts with the first character of this char sequence.

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

Samples

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

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

Parameters

operation

function that takes current accumulator value and a character, and calculates the next accumulator value.