flatMap

Transforms each element into an Iterable of results and flattens all results into a single 1D array. Useful when each element maps to a variable number of output values.

Signatures

inline fun <T, D : Dimension, reified R> MultiArray<T, D>.flatMap(
    transform: (T) -> Iterable<R>
): D1Array<R>

inline fun <T, reified R> MultiArray<T, D1>.flatMapIndexed(
    transform: (index: Int, T) -> Iterable<R>
): D1Array<R>

inline fun <T, reified R> MultiArray<T, D1>.flatMapMultiIndexed(
    transform: (index: IntArray, T) -> Iterable<R>
): D1Array<R>

Parameters

Parameter	Type	Description
`transform`	`(T) -> Iterable<R>`	Maps each element to an iterable of results.
`transform`	`(index: Int, T) -> Iterable<R>`	With flat index (1D arrays only).
`transform`	`(index: IntArray, T) -> Iterable<R>`	With multi-dimensional index.

Returns: D1Array<R> — all results flattened into a single 1D array.

Example

val a = mk.ndarray(mk[1, 2, 3])

val result = a.flatMap { listOf(it, it * 10) }
// [1, 10, 2, 20, 3, 30]

28 February 2026