arximboldi

immer

C++2016–2026

arximboldi / immer

immer

Postmodern immutable and persistent data structures for C++ — value semantics at scale

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21Distinct people

34Mentions

3Explicit recommenders

2.9KGitHub stars

REPOSITORY AT A GLANCE

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What it is

Postmodern immutable and persistent data structures for C++ — value semantics at scale

GitHub

Where it is used

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What people are saying

My hobby language[1] also has no reference semantics, very similar to Herd. I think this is a really interesting point in the design space. A lot of complexity goes away when…

electroly used a recommendation phrase. 3 indexed comments match. This is a phrase match, not a verdict.

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Also in these discussions

arximboldi/ewig · linked in 6 of the same discussions
arximboldi/lager · linked in 6 of the same discussions

Mentioned in the same Hacker News threads. That is not proof they are substitutes.

This week on Hacker News

Nov 8–Nov 15 UTC · Direct repository links and separately labeled related project stories. Indexed through 11/15/2026, 2:04:58 PM UTC.

No direct repository links were found in the indexed HN discussions over the past seven days. Older discussions are available below.

Mentions over time

HN mentions by year34 dated mentions

Observed mentions: 2016-11-27 16:12:55 UTC to 2026-02-15 06:31:32 UTC.

* An incomplete calendar period is marked with an outlined bar. Its count is not directly comparable with a full period.

Counts come from the repository’s dated source evidence. Index cutoff: 2026-11-02 08:16:59 UTC.

View mention counts and date ranges

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Period	Start (UTC)	End (exclusive, UTC)	Mentions	Submissions	Comments
2016	2016-01-01 00:00:00 UTC	2017-01-01 00:00:00 UTC	1	1	0
2017	2017-01-01 00:00:00 UTC	2018-01-01 00:00:00 UTC	7	0	7
2018	2018-01-01 00:00:00 UTC	2019-01-01 00:00:00 UTC	1	0	1
2019	2019-01-01 00:00:00 UTC	2020-01-01 00:00:00 UTC	3	1	2
2020	2020-01-01 00:00:00 UTC	2021-01-01 00:00:00 UTC	5	0	5
2021	2021-01-01 00:00:00 UTC	2022-01-01 00:00:00 UTC	3	0	3
2022	2022-01-01 00:00:00 UTC	2023-01-01 00:00:00 UTC	4	1	3
2023	2023-01-01 00:00:00 UTC	2024-01-01 00:00:00 UTC	6	1	5
2024	2024-01-01 00:00:00 UTC	2025-01-01 00:00:00 UTC	1	0	1
2025	2025-01-01 00:00:00 UTC	2026-01-01 00:00:00 UTC	1	1	0
2026 (partial)	2026-01-01 00:00:00 UTC	2027-01-01 00:00:00 UTC	2	0	2

What Hacker News says

7 sources

arximboldi·Dec 9, 2017

I am working on something like that for C++, a library + debugger called Lager. Quite experimental yet, but been using it to write apps with SDL and Ncurses and I am happy with how it is going... In the end it is a very simple architecture, implementable in any language. Good immutable data-structures are important for big programs though. Library: https://github.com/arximboldi/lager Ncurses example (full text-editor): https://github.com/arximboldi/ewig SDL example: https://twitter.com/sinusoidalen/status/939539173584916480 Immutable data: https://github.com/arximboldi/immer (There was a talk about Lager at MeetingCpp this year, still waiting for it to be published online...)

In Git is a purely functional data structure (2013)

arximboldi·Nov 26, 2017

I really want to like Carp but I somehow feel that the Rusty memory model does not fit the Lisp philosophy... all the borrowing story comes from a basis mutability. I wish for something more Clojurish based on immutable data. Then one can exploit the power of inferred type linearity/affinity to transparently build safe "transients" and other cool stuff. Maybe some day I should write such Lisp myself on top of my C++ immutable data structures [1] :-) [1] https://github.com/arximboldi/immer

In Carp, a compiled Lisp with type inference and a borrow checker

arximboldi·Nov 8, 2017

My most popular open-source project [1] I talk about at conferences, mostly C++ ones (last example [2]). I was lucky to also land a paper about it at ICFP'17 [3]. On Friday I will talk at the MeetingCpp conference in Berlin about a new library I am building (kind of experimental Redux for C++ with time-travelling debugger!). I work as a freelancer and at the moment I do client work 3 days a week and dedicate the rest of the time to the open-source work. The open-source work includes doing research and implementing these tools, but also preparing the talks, which is a very time consuming task for me. Doing conference talks is very emotionally exhausting, I dread the previous weeks to the talk---but the feeling afterwards is very good and it is a good way to get exposure, I hope. My dream is to some day form a social company with a coop

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structure that works full-time on open-source, either directly or indirectly helping clients use these tools in their system. I hope I am set up in the right direction. Recently I opened a Twitter account to talk mostly about my open-source stuff [1]. I admittedly hate Twitter as a social network, but I've been convinced that it is a good place for networking in our industry, so I just play the game. I keep telling myself that I should open blog too, but then I realize that one can't simply do everything all the time, so I guess maybe I'll never do it. To your last question: is it unfair to not do marketing to your work? Totally not. Just do whatever feels right to you. If one day you realize you have built something really useful, probably you'll get the urge to tell people about it. [1] Immutable data-structures for C++: https://github.com/arximboldi/immer Example usage: https://github.com/arximboldi/ewig [2] https://www.youtube.com/watch?v=sPhpelUfu8Q [3] https://public.sinusoid.es/misc/immer/immer-icfp17.pdf [4] https://twitter.com/sinusoidalen

In Ask HN: How much time do you spend on “marketing” your open source projects?

Johnny_Brahms·Oct 2, 2017

Y'all should have a look at ewig which uses Immer - really fast persistent data structures for c++. Ewig is just a proof of concept, but the code is really nice. I have thought about taking that and building something bigger. The upsides are the same as for a piece table (really simple undo/redo) but with the downside of not being able to just mmap a file. You also get basically zero memory usage when you do cut and paste (you can paste a file into itself until it is bigger than RAM without problems, since you are actually not copying the contents, just the pointer) Look at the YouTube video as well. It is all very cool, at least if you are not already spoiled by using clojure :) https://github.com/arximboldi/immer/blob/master/README.rst Edit: Forgot to mention: Ewig can be found among Immer's author Arximboldi's repos. On my phone right

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now on GPRS connection, so maybe another friendly soul can provide the link.

In Text Editor: Data Structures

arximboldi·Aug 28, 2017

Very interesting work! It seems that educational text editors are becoming a trend after Antirez published his :-) Excuse me the shameless plug, I'd like to show mine too: https://github.com/arximboldi/ewig It is written in C++, but using a style that is unlike what most C++ developers use: it is composed mostly of pure functions. The architecture is very much like that of Elm programs, and there is even a `store` class like in Redux. Like the project from OP, it is about 2K lines of code. But it also supports asynchronous loading/saving, copy-paste (you can copy-paste a 1GB file instantly), very robust undo, dirty markers, UTF-8 (not perfect), etc. The magic? Immutable vectors based on RRB-Trees. This is like the vectors in Clojure/Scala, but also supports log(n) slicing, concatenations, insertions---these operations are fundamental

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for a text editor, and I'd say, to most interactive software supporting big data models [1]. The code has been written in a style as simple as I could. I'd like to think that even non-C++ developers might be able to understand it. It might be specially interesting for web developers invested in Clojure, Elm or Redux and the single-atom architecture. Probably one day I should go ahead and just write a blog post about it or a tutorial or something. But so far I don't have a blog I am not really a social media person. The code is still moving also... PS. And thanks a lot to @kostspielig her help writing and reviewieng the code! <3 [1] The data-structure can be found here: https://github.com/arximboldi/immer

In Lessons learned from implementing a text editor related to front-end development

arximboldi·Aug 4, 2017

There are many things to love in Clojure, like core.async, the lispyness, etc. But for me, their biggest breakthrough is with no doubt the data-structures. Clojure default of immutable hash maps and vectors was really bold. They had to innovate by giving a twist to Bagwell's great research on data-structures, and they managed to build what in my opinion are the first set of general data-structures suitable of representing traditional hierarchical object-tree data-models immutably, at the scale of large interactive software. Without these, the single-atom architecture that now is popular as ever with Redux, Elm, etc. would not be possible. The flourishing of functional programming for interactive software that followed shows to me that the biggest impediment before was not the lack of functional ways of expressing interactions (the Hask

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ell people have devoted a lot of notable effort in the FRP camp). Instead, just having efficient data-structures to write persistent document models, escaping the rigidity of lists and rb-trees, allows you to write big interactive sofware in a functional manner even with the most dumb abstractions (which is a good thing, KISS!) and even stupid language (JavaScript!). This has inspired me to work on a generic implementation in C++, which also has experimental Python and Guile bindings: https://sinusoid.es/immer/ https://github.com/arximboldi/immer/ In the past I also did some other work on bringing Clojure Transducers to C++ (https://www.youtube.com/watch?v=vohGJjGxtJQ&t=1614s) but I know consider it a much less important effort---without the data-structures the other parts of Clojure feel almost like just sugar. EDIT1 -- Sorry for the shameless plug ;) EDIT2 -- Grammar

In Clojure will affect the way you think about programming

arximboldi·Apr 17, 2017

Interesting! I find it amazing that they went all the way into implementing a CDRT to support efficient plugins. At the moment I am also writing a text-editor with my partner, to show-case the C++ RRB-Trees implementations in Immer [1]. We are just started, but my plan is to stop at 1000k lines. Interestingly, with such persistent data structure, you go already a long way in implementing undo, parallel processing, and many editing algorithms are super simple thanks to slicing/concat. Memory consumption is still sub-optimal (also I am using wchar_t to simplify my life), but I am very satisfied with the results so far (it is the fastest editor I have on my machine when editing 1GB file, also can edit a ~100MB file on a Raspberry --- larger files fail only due to excessive memory use :/). [1] https://github.com/arximboldi/immer

In Rope Science – Computer science concepts behind the Xi editor