Universal operations

Overview

Universal operations are extension functions on MultiArray<T, D> that follow Kotlin collection conventions. They provide familiar APIs for transforming, filtering, aggregating, and converting arrays.

Predicates

Function	Description
all	`true` if all elements match a predicate.
any	`true` if at least one element matches.
contains	`true` if the array contains a given element.

Traversal

Function	Description
forEach	Apply an action to each element.
onEach	Apply an action to each element and return the array.

Transformation

Function	Description
map	Transform each element, preserving shape.
flatMap	Transform each element into an iterable, flatten to 1D.
scan	Running accumulation, returning all intermediate values.
append	Append elements or another array.
repeat	Tile elements n times into a flat 1D array.
clip	Clamp every element to a `min..max` range.

Filtering

Function	Description
filter	Elements matching a predicate, returned as 1D.
find	First element matching a predicate, or `null`.
distinct	Unique elements as a 1D array.

Aggregation

Function	Description
fold	Accumulate from an initial value.
reduce	Accumulate without an initial value.
sum	Sum of all elements.
average	Average of all elements.
count	Count elements, optionally matching a predicate.
max	Largest element, or `null` if empty.
min	Smallest element, or `null` if empty.
maximum	Element-wise maximum of two arrays.
minimum	Element-wise minimum of two arrays.

Search

Function	Description
first	First element, or first matching a predicate.
last	Last element, or last matching a predicate.
indexOf	Flat index of the first occurrence, or `-1`.

Ordering

Function	Description
sorted	New array with elements sorted.
reversed	New array with elements in reverse order.

Partitioning

Function	Description
partition	Split into (matching, non-matching) pair.
chunked	Split into fixed-size chunks as a 2D array.
windowed	Sliding window as a 2D array.
drop	Drop the first n elements (1D only).

Grouping

Function	Description
groupNDArray	Group elements by key into a map of 1D arrays.
associate	Build a map from key-value pairs.
intersect	Set intersection with another collection.

Conversion

Function	Description
toList	Flat `List<T>` of all elements.
toCollection	Append all elements to a mutable collection.
toPrimitiveArray	Convert to a Kotlin primitive array.
toArray	Convert to nested Kotlin arrays.
asSequence	Lazy `Sequence<T>` over elements.
toType	Convert element type (e.g. `Int` to `Double`).
joinTo	Build a string representation.

28 February 2026