kotlin-stdlib / kotlin.sequences / reduceOrNull

reduceOrNull

Common
JVM
JS
Native
1.3
@ExperimentalStdlibApi inline fun <S, T : S> Sequence<T>.reduceOrNull(
    operation: (acc: S, T) -> S
): S?

Accumulates value starting with the first element and applying operation from left to right to current accumulator value and each element. Returns null if the sequence is empty.

The operation is terminal.

import kotlin.test.*

fun main(args: Array<String>) {
//sampleStart
val strings = listOf("a", "b", "c", "d")
println(strings.reduceOrNull { acc, string -> acc + string }) // abcd

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