kotlin-stdlib/kotlin.collections/foldIndexed

foldIndexed

inline fun <T, R> Array<out T>.foldIndexed(initial: R, operation: (index: Int, acc: R, T) -> R): R(source)
inline fun <R> ByteArray.foldIndexed(initial: R, operation: (index: Int, acc: R, Byte) -> R): R(source)
inline fun <R> ShortArray.foldIndexed(initial: R, operation: (index: Int, acc: R, Short) -> R): R(source)
inline fun <R> IntArray.foldIndexed(initial: R, operation: (index: Int, acc: R, Int) -> R): R(source)
inline fun <R> LongArray.foldIndexed(initial: R, operation: (index: Int, acc: R, Long) -> R): R(source)
inline fun <R> FloatArray.foldIndexed(initial: R, operation: (index: Int, acc: R, Float) -> R): R(source)
inline fun <R> DoubleArray.foldIndexed(initial: R, operation: (index: Int, acc: R, Double) -> R): R(source)
inline fun <R> BooleanArray.foldIndexed(initial: R, operation: (index: Int, acc: R, Boolean) -> R): R(source)
inline fun <R> CharArray.foldIndexed(initial: R, operation: (index: Int, acc: R, Char) -> R): R(source)

Accumulates value starting with initial value and applying operation from left to right to current accumulator value and each element with its index in the original array.

Returns the specified initial value if the array is empty.

Parameters

operation

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

inline fun <T, R> Iterable<T>.foldIndexed(initial: R, operation: (index: Int, acc: R, T) -> R): R(source)

Accumulates value starting with initial value and applying operation from left to right to current accumulator value and each element with its index in the original collection.

Returns the specified initial value if the collection is empty.

Parameters

operation

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

@ExperimentalUnsignedTypes
inline fun <R> UIntArray.foldIndexed(initial: R, operation: (index: Int, acc: R, UInt) -> R): R(source)
@ExperimentalUnsignedTypes
inline fun <R> ULongArray.foldIndexed(initial: R, operation: (index: Int, acc: R, ULong) -> R): R(source)
@ExperimentalUnsignedTypes
inline fun <R> UByteArray.foldIndexed(initial: R, operation: (index: Int, acc: R, UByte) -> R): R(source)
@ExperimentalUnsignedTypes
inline fun <R> UShortArray.foldIndexed(initial: R, operation: (index: Int, acc: R, UShort) -> R): R(source)

Accumulates value starting with initial value and applying operation from left to right to current accumulator value and each element with its index in the original array.

Returns the specified initial value if the array is empty.

Since Kotlin

1.3

Parameters

operation

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