Is there a KD-tree?

[njlr]

Is there a KD-tree implementation under a different name?

If not, would a PR be accepted?

[gdziadkiewicz]

Sorry for late reply, a PR would totally be accepted Sent from Outlook for Android<https://aka.ms/AAb9ysg>

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________________________________ From: njlr ***@***.***> Sent: Tuesday, December 9, 2025 11:11:06 AM To: fsprojects/FSharpx.Collections ***@***.***> Cc: Subscribed ***@***.***> Subject: [fsprojects/FSharpx.Collections] Is there a KD-tree? (Issue #218) [https://avatars.githubusercontent.com/u/1577531?s=20&v=4]njlr created an issue (fsprojects/FSharpx.Collections#218)<#218> Is there a KD-tree implementation under a different name? If not, would a PR be accepted? — Reply to this email directly, view it on GitHub<#218>, or unsubscribe<https://github.com/notifications/unsubscribe-auth/ACBG4D2IZIJ6UNWE52AXRRT4A2N3VAVCNFSM6AAAAACOPHNSDOVHI2DSMVQWIX3LMV43ASLTON2WKOZTG4YTAMJVGY4TCMQ>. You are receiving this because you are subscribed to this thread.Message ID: ***@***.***>

[github-actions]

🤖 This is an automated response from Repo Assist.

Glad to hear a KD-tree PR would be welcome! To help get started, here are some notes on how to fit such a contribution into this repo:

Where to put it

New structures typically land in FSharpx.Collections.Experimental first (in src/FSharpx.Collections.Experimental/), which reduces the review bar for novel data structures. Once they've proven stable and tested they can be promoted to the core library — see #122 for that discussion.

What to implement

A minimal 2D/k-D immutable KD-tree in F# usually looks like:

type KdTree<'T> =
    | Leaf
    | Node of point: float[] * value: 'T * left: KdTree<'T> * right: KdTree<'T>

Essential module functions to include (mirroring the style of this repo):

• empty, insert, nearestNeighbour (or nearest), rangeSearch, toSeq
• tryNearest returning an option

Testing

Tests go in tests/FSharpx.Collections.Experimental.Tests/. The project uses Expecto — look at HeapTest.fs or PersistentHashMapTest.fs for style examples. Property-based tests via FsCheck are also welcome.

Checklist before opening the PR

1. Run ./build.sh CheckFormat — CI enforces Fantomas formatting.
2. Run ./build.sh RunTests — all tests must pass.

Feel free to ask questions here if you run into issues — happy to help!

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