kotlin-data-ref provides small identity-based collection helpers for Kotlin Multiplatform code.

Use it when object identity matters more than structural equality: graph algorithms, object interning, cycle detection, memoization keyed by object references, and diagnostics that need to distinguish equal-but-distinct objects.

commonMain.dependencies {
    implementation("one.wabbit:kotlin-data-ref:1.1.1")
}

import one.wabbit.data.Ref
import one.wabbit.data.identitySetOf

data class Node(val id: Int)

val a = Node(1)
val b = Node(1)

check(a == b)
check(Ref(a) != Ref(b))

val nodes = identitySetOf(a, b)
check(nodes.size == 2)

Ref delegates hashing to the platform identity hash code and compares wrapped values with ===. That makes it suitable as a key when the wrapped type has structural equals/hashCode behavior that you explicitly do not want.

Ref.toString() is diagnostic-only. For non-null values it includes a platform class name and unsigned hexadecimal identity hash; for null it returns Ref[null]. The exact output should not be parsed.

This library is small and stable in scope, but it is still pre-2.0. Public API changes should be rare and documented in release notes.

import one.wabbit.data.identityMap
import one.wabbit.data.identitySetOf

val first = String(charArrayOf('x'))
val second = String(charArrayOf('x'))

val set = identitySetOf(first, second)
check(set.size == 2)

val map = identityMap<String, Int>()
map[first] = 1
map[second] = 2

check(map[first] == 1)
check(map[second] == 2)

import one.wabbit.data.distinctByIdentity

val item = Any()
val values = listOf(item, Any(), item)

check(values.distinctByIdentity().size == 2)

The iterable overload returns a List. The sequence overload filters lazily and keeps one identity set of already-seen references for the duration of iteration.

• 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.

Contributions are governed by the repository contribution policy and the Wabbit CLA. See CONTRIBUTING.md and the files under legal/.