reduceIndexed
inline
fun
<
S
,
T
:
S
>
Array
<
out
T
>
.
reduceIndexed
(
operation
:
(
index
:
Int
,
acc
:
S
,
T
)
->
S
)
:
S
(source)
inline
fun
ShortArray
.
reduceIndexed
(
operation
:
(
index
:
Int
,
acc
:
Short
,
Short
)
->
Short
)
:
Short
(source)
inline
fun
FloatArray
.
reduceIndexed
(
operation
:
(
index
:
Int
,
acc
:
Float
,
Float
)
->
Float
)
:
Float
(source)
inline
fun
DoubleArray
.
reduceIndexed
(
operation
:
(
index
:
Int
,
acc
:
Double
,
Double
)
->
Double
)
:
Double
(source)
inline
fun
BooleanArray
.
reduceIndexed
(
operation
:
(
index
:
Int
,
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 with its index in the original array.
Throws an exception if this array is empty. If the array can be empty in an expected way,
please use
reduceIndexedOrNull
instead. It returns
null
when its receiver is empty.
import kotlin.test.*
fun main(args: Array<String>) {
//sampleStart
val strings = listOf("a", "b", "c", "d")
println(strings.reduce { acc, string -> acc + string }) // abcd
println(strings.reduceIndexed { index, acc, string -> acc + string + index }) // ab1c2d3
// emptyList<Int>().reduce { _, _ -> 0 } // will fail
//sampleEnd
}
Parameters
operation
- function that takes the index of an element, current accumulator value and the element itself,
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 with its index in the original collection.
Throws an exception if this collection is empty. If the collection can be empty in an expected way,
please use
reduceIndexedOrNull
instead. It returns
null
when its receiver is empty.
import kotlin.test.*
fun main(args: Array<String>) {
//sampleStart
val strings = listOf("a", "b", "c", "d")
println(strings.reduce { acc, string -> acc + string }) // abcd
println(strings.reduceIndexed { index, acc, string -> acc + string + index }) // ab1c2d3
// emptyList<Int>().reduce { _, _ -> 0 } // will fail
//sampleEnd
}
Parameters
operation
- function that takes the index of an element, current accumulator value and the element itself,
and calculates the next accumulator value.