filter

Returns a 1D array containing only the elements that satisfy the given predicate. Indexed variants allow filtering based on element position. filterNot inverts the predicate. The result is always 1D regardless of the input dimensionality.

Signatures

inline fun <T, D : Dimension> MultiArray<T, D>.filter(
    predicate: (T) -> Boolean
): D1Array<T>

inline fun <T> MultiArray<T, D1>.filterIndexed(
    predicate: (index: Int, T) -> Boolean
): D1Array<T>

inline fun <T, D : Dimension> MultiArray<T, D>.filterMultiIndexed(
    predicate: (index: IntArray, T) -> Boolean
): D1Array<T>

inline fun <T, D : Dimension> MultiArray<T, D>.filterNot(
    predicate: (T) -> Boolean
): D1Array<T>

Parameters

Parameter	Type	Description
`predicate`	`(T) -> Boolean`	Condition to match.
`predicate`	`(index: Int, T) -> Boolean`	Condition with flat index (1D arrays only).
`predicate`	`(index: IntArray, T) -> Boolean`	Condition with multi-dimensional index.

Returns: D1Array<T> — a flat 1D array of matching elements.

Example

val a = mk.ndarray(mk[mk[1, 2, 3], mk[4, 5, 6]])

a.filter { it > 3 }                       // [4, 5, 6]
a.filterNot { it > 3 }                    // [1, 2, 3]

val b = mk.ndarray(mk[10, 20, 30, 40])
b.filterIndexed { i, v -> i % 2 == 0 }    // [10, 30]

28 February 2026