P-p-hk·Feb 19, 2025
I can't vouch for them, but there are Clojure[1] and C[2] implementations you might consider.
[1] https://github.com/clojure/core.rrb-vector
[2] https://github.com/hyPiRion/c-rrb
In Relaxed Radix Balanced Trees (2024)clojure
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RRB-Trees in Clojure
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| Period | Start (UTC) | End (exclusive, UTC) | Mentions | Submissions | Comments |
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| 2013 | 2013-01-01 00:00:00 UTC | 2014-01-01 00:00:00 UTC | 1 | 0 | 1 |
| 2014 | 2014-01-01 00:00:00 UTC | 2015-01-01 00:00:00 UTC | 2 | 0 | 2 |
| 2015 | 2015-01-01 00:00:00 UTC | 2016-01-01 00:00:00 UTC | 1 | 0 | 1 |
| 2016 | 2016-01-01 00:00:00 UTC | 2017-01-01 00:00:00 UTC | 0 | 0 | 0 |
| 2017 | 2017-01-01 00:00:00 UTC | 2018-01-01 00:00:00 UTC | 1 | 0 | 1 |
| 2018 | 2018-01-01 00:00:00 UTC | 2019-01-01 00:00:00 UTC | 0 | 0 | 0 |
| 2019 | 2019-01-01 00:00:00 UTC | 2020-01-01 00:00:00 UTC | 0 | 0 | 0 |
| 2020 | 2020-01-01 00:00:00 UTC | 2021-01-01 00:00:00 UTC | 0 | 0 | 0 |
| 2021 | 2021-01-01 00:00:00 UTC | 2022-01-01 00:00:00 UTC | 0 | 0 | 0 |
| 2022 | 2022-01-01 00:00:00 UTC | 2023-01-01 00:00:00 UTC | 0 | 0 | 0 |
| 2023 | 2023-01-01 00:00:00 UTC | 2024-01-01 00:00:00 UTC | 0 | 0 | 0 |
| 2024 | 2024-01-01 00:00:00 UTC | 2025-01-01 00:00:00 UTC | 0 | 0 | 0 |
| 2025 | 2025-01-01 00:00:00 UTC | 2026-01-01 00:00:00 UTC | 1 | 0 | 1 |
What Hacker News says
6 sourcesDo you mean https://en.wikipedia.org/wiki/Persistent_data_structure or something more specific for this case? It's known how to only incur an O(1) cost in time and space for making a data structure persistent. So then you just need to keep a reference to all past versions of the data structure you might ever want to undo back to.
EDIT: actually reading the wiki more carefully, I think they were talking about making a BST persistent specifically rather than any data structure. In that case looking at implementations such as rrb-vectors might be more interesting: https://github.com/clojure/core.rrb-vector
In What's been wrought using the Piece Table? (2014)Clojure's built in PersistentVector does not support O(log(n)) inserts/removes from the middle/front, but there is another implementation that shares a lot of it's implementation with some extensions that does: https://github.com/clojure/core.rrb-vector/
In Persistent Vector Performance, summarisedMaybe mori could include core.rrb-vector[1]. Other interesting persistent data structures (by the same author) are persistent sorted maps and sets[2].
[1] https://github.com/clojure/core.rrb-vector
[2] https://github.com/clojure/data.avl
In Elm 0.12.1: Fast immutable arraysSome time ago, hypirion wrote about how persistent vectors are implemented in Clojure.
http://hypirion.com/musings/understanding-persistent-vector-...
There are actually several different implementations of the core data structures:
https://github.com/clojure/data.finger-tree
https://github.com/clojure/core.rrb-vector
Of course, the short answer is that Clojure isn't using classic linked lists, and that regular Java collections can be used and created pretty easily. [0] [1]
[0] https://stackoverflow.com/questions/4313505/converting-cloju...
[1] http://blog.raek.se/2011/01/24/executors-in-clojure/
In Data Structures in Clojure: Singly-Linked ListsClojure's standard persistent vectors don't allow insertion in the middle without copying the entire vector, they only allow fast insertion at the end. There is an alternative implementation here [1] which does allow insertion (anywhere) without copying the entire vector.
[1] https://github.com/clojure/core.rrb-vector
In Understanding Clojure's Persistent Vectors, Part 1