reduceOrNull
inline fun BooleanArray.reduceOrNull(
operation: (acc: Boolean, Boolean) -> Boolean
): Boolean?
(source)
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 array is empty.
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(strings.reduceIndexedOrNull { index, acc, string -> acc + string + index }) // ab1c2d3
println(emptyList<String>().reduceOrNull { _, _ -> "" }) // null
//sampleEnd
}
Parameters
operation
- function that takes current accumulator value and an element,
and calculates the next accumulator value.
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 collection is empty.
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(strings.reduceIndexedOrNull { index, acc, string -> acc + string + index }) // ab1c2d3
println(emptyList<String>().reduceOrNull { _, _ -> "" }) // null
//sampleEnd
}
Parameters
operation
- function that takes current accumulator value and an element,
and calculates the next accumulator value.