kotlin-data is a Kotlin Multiplatform collection and data-structure library for compact immutable collections, mutable primitive buffers, persistent queues and heaps, and small functional result types.

It is intended for projects that need predictable data-structure behavior without pulling in a large runtime. The library includes immutable value-oriented containers such as Arr, ArrMap, Chain, Chunk, ConsList, LazyList, and BankersQueue; mutable primitive buffers and deques; and functional types such as Option, Either, and Validated.

repositories {
    mavenCentral()
}

dependencies {
    implementation("one.wabbit:kotlin-data:3.0.0")
}

import one.wabbit.data.Arr
import one.wabbit.data.Option
import one.wabbit.data.Validated
import one.wabbit.data.arrOf

val values = arrOf(1, 2, 3)
val doubled: Arr<Int> = values.map { it * 2 }

val maybeFirst: Option<Int> =
    Option.of(values.firstOrNull())

val checked: Validated<String, Int> =
    Validated.succeed(doubled.last())

check(doubled.toList() == listOf(2, 4, 6))
check(maybeFirst.orNull() == 1)
check(checked is Validated.Success)

• Arr and ArrMap: compact immutable array-backed sequence and small-map types.
• Chunk, Chain, ConsList, and LazyList: collection building blocks for persistent and lazy workflows.
• BankersQueue and LeftistHeap: persistent queue and priority-queue structures.
• BooleanBuffer, IntBuffer, DoubleBuffer, and other primitive buffers: mutable contiguous buffers without boxing.
• BooleanDeque, IntDeque, DoubleDeque, and other primitive deques: mutable ring-buffer deques for both-end operations.
• Option, Either, and Validated: small functional result/value types.
• JVM/Android helpers for weak sets/maps, UUID byte conversion, enum-set copying, and deterministic shuffling.

Primitive buffers are mutable and own their internal arrays:

import one.wabbit.data.IntBuffer

val buffer = IntBuffer.of(1, 2, 3)
buffer.add(4)
val removed = buffer.removeAt(0)

check(removed == 1)
check(buffer.toList() == listOf(2, 3, 4))

Buffers support negative indices for documented element access and update operations. Range-style operations clamp like Python slices where documented.

import one.wabbit.data.BankersQueue

val queue = BankersQueue.empty<String>()
    .enqueue("first")
    .enqueue("second")

val next = queue.dequeueOrNull()

check(next?.first == "first")
check(next?.second?.peekOrNull() == "second")

This library is stable enough for internal production use, but the public API is still broad and evolving. Expect documentation and compatibility notes to be maintained as part of publication prep; avoid depending on undocumented implementation details or internal storage classes.

• User guide
• API reference notes
• Troubleshooting
• Development

Generated API docs can be built locally with Dokka. See API reference notes for the command.

• CHANGELOG.md

This project is licensed under the GNU Affero General Public License v3.0 (AGPL-3.0) for open source use.

For commercial use, contact Wabbit Consulting Corporation at wabbit@wabbit.one.

Before contributions can be merged, contributors need to agree to the repository CLA.