I've been meaning to try this out, from my read it's a declarative way to get some structured concurrency. I work in a codebase that heavily uses core.async channels to manage concurrency and you really need to pay close attention to error handling. When you're spawning new threads you need to set up your own custom machinery to re-throw errors on a chans, close chans, and it looks like core.async.flow is a way to do all of this declaratively.
Just like `core.async` itself was a frontrunner of Virtual Threads on the JVM, I view `core.async.flow` as the Clojure version of the upcoming [0]Structured Concurrency JEP. I do wonder if it will use that under the hood once it becomes stable, the same way `core.async` is planning to move away from the `go` macro to just have it dispatch a virtual thread.
For me, the real 'click' moment with core.async wasn't just about replacing callbacks. It was realizing I could model entire business processes as a system of communicating channels. It completely changed how I think about system design.
The language itself is still getting updates, a new major release was just dropped a month or two ago.
I do find that for about 5 years things seemed to be slowing down. Though I keep seeing it pop up, and new exciting projects seem to pop up from time to time.
Just today I saw an article about Dyna3, a relational programming language for AI and ML that was implemented on top of Clojure.
I miss the Strange Loop conference. I think a lot of Clojure buzz was generated there. Clojure West and a few others so a decent job, but the quality of the talks at Strange Loop were second to none. Not that it was a Clojure specific conference, but it had that focus on elegance that I don't see very often, and the organizer was a something like the Prince of Clojure, if I recall correctly.
I'm still enjoying the language, and all my projects still build and run just fine.
The major frustration I have with the platform is 3D graphics. That's a JVM issue overall though.
They even invited Guy Lewis Steele, Jr. hos talk is on YouTube and was awesome. His meta-notation is explained more expansively in a paper on his Oracle page.
As others have said, Clojure is still a thing. For anyone catching up with Clojure again after some time: check out Babashka! Think bash scripts, written in Clojure. It's delightful.
I still use it. They finally fixed my biggest complaint about it a year ago, which is that you couldn't use vanilla Clojure lambdas for the Java functional interface, and so you'd have to reify that interface and it was bulky and ugly. Now it works fine so long as the interfaces actually have the @FunctionalInterface attribute.
Not every project uses @FunctionalInterface, but I've been trying to add it to places [1] [2] [3], and now I'm able to use Clojure in a lot more places.
I’d say clojure is very alive and happy. I’m a clojure newb and have been having a super fun time getting into it. Lots of very neat tools are in active development (babashka is the best thing that’s happened to my developer life in a while!!)
The small-medium sized community is actually fantastic for learning. The big names in the community are only a slack away, and everybody is so enthusiastic.
I was asking the same question today after investigating XTDB¹ (a Clojure centric bitemporal DB) and went looking for a batteries included WebAssembly framework like Blazor²
It is, but the community has been shrinking in recent years.
FWIW, Google Trends shows the hype peaking in 2016, but I doubt that reflects usage as much as buzz.
Instead, if you look at the annual State of Clojure survey results, which solicits opinions directly from the community, the number of responders peaked in 2020 at ~2500, and is down to ~1500 for the most recent 2024 survey.
- 2024 Highlights
- Trends Over Time
- 2024 New Users
- Previous Results
Now... If we are pointing out isolated facts to make an argument, I would caution that survey popularity (sensitive to timing, duration, outreach etc.) is less telling---and less statistically significant---than isolated facts like this:
> Clojure versions
> Clojure 1.12.0 was released in September 2024 and the survey showed rapid uptake, with 58% already using it, and 65% developing or deploying with the prior versions 1.11, and a steep drop-off after that. Clojure’s focus on stability and avoiding breaking changes makes upgrades safe and easy.
> Trends (use at work, hobby, and study have all up-trended)
> Because this survey has been running since 2010 (thanks to Chas Emerick originally!), we have lots of great longitudinal data and it’s interesting to compare some of the answers over time.
> Looking at the question of how Clojure developers use Clojure, we can see this has generally trended more towards using it at work. However, this year we saw an uptick of people using it for hobbies or in their studies:
Everything you quoted is based on percentages of the responders, not absolute numbers. Changing in-group proportions don't say anything about overall usage. E.g., if responder work usage goes up 10%, but 40% fewer people use Clojure, that's still a drop in absolute numbers.
Look for the number of responses, and you can see a decline each year after 2020.
---
It's possible that the survey may not have been advertised as well, but afaik, it's still posted the same way it always was: announcements on Clojurians, Clojureverse, reddit, etc. I haven't heard of any reason that survey numbers would have been artificially depressed for several years running.
This is cool. So basically you create a group of threads and you can treat them as one unit. Trio does something similar (structured concurrency) with async functions for Python. Are these OS threads or green threads?
This is really interesting, although I still can't get my head around the fact that core.async.flow topologies are immutable. I feel like most problems can't be solved with fixed topologies.
I guess one could in theory swap flows the same way values are swapped, but I wonder if this is the way this library is supposed to be used. I also wonder what happens to non-empty channel buffers in this case.
I think LISP is cool and want to use it more but I have 0 appetite to learn the toolchain and debug etc for JVM. You have Racket but Clojure ecosystem is already tiny.
That’s a common misconception. JVM toolchain is way better than the hellscape that are most other language ecosystems. Maven, for example, works reliably and is rock-solid. The only unsolved problem is if you get two libraries/frameworks requesting another dependency, but with different incompatible versions. But I don’t think most other ecosystems solve that painlessly either.
Debug specifically is state-of-the-art. Look at YourKit, or any debugger included with common IDEs.
None of those tools has a shiny Visual 2025 aesthetic, but again, they work reliably and are going to work the same way a year from now.
Indeed, JVM and .NET are the only two major ecosystems out the whole Xerox PARC ideas[0], and the reason that to this day they are my two main workhorses, plus JS runtimes, because Web.
[0] - Technincally Objective-C and Swift could also be considered, but they lack the industry wide adoption, as many cool tools only exist in Apple land.
Leiningen and deps.edn shield you a bit from the awfulness of Java project management. They feel a lot more like something you'd see in Node.js or something, but it still gets dependencies from Maven Central.
Debugging and profiling is still somewhat Java based, and yeah that's can be irritating, but you get used to it.
Personally I do think that it's worth it; Clojure is a very pleasant language that has no business being as fast as it is, and core.async is an absolutely lovely concurrency framework if you can convert your logic into messaging, and you have Haskell-style transactional memory for stuff that can't be. So many problems become less irritating in Clojure.
Funny. I was just thinking about dismissing Clojure for a project I'm going to work on because I was concerned about it's lack of ability to work with async calls. I'm too used to how async in JavaScript and C#, and I'm not sure I'd want to work in an environment that doesn't have a simple way to structure async calls. It doesn't necessarily have to be async / await. Just some attention to the issue rather than completely ignoring it.
That has always been one of Clojure's main strengths (async & concurrency). With the new JVM VirtualThreads, things are looking better than ever.
The transition of core.async specifically to VirtualThreads is still WIP as far as I understand, but with minimal tweaks, 90% of the benefits are already there, even with the current latest version.
Choose core.async.flow when you want a declarative, monitorable process graph over channels (pause/resume, error channel, flow monitor).
Choose Manifold when you need deferreds/streams as general primitives, precise per-op backpressure, error-aware chaining, or you’re in the Aleph/Netty stack.
very abstract but based on this, the answer is no.
typos (from a quick surface scan; I'm not familiar with Clojure or this package):
"The description arity takes the current state ..." should be "The transition arity takes the current state ..."
"excepiton" should be "exception"
"Exceptions thrown from the transition or transform arities, the exception ..." should be "If exceptions are thrown from the transition or transform arities, they ..."
I've been meaning to try this out, from my read it's a declarative way to get some structured concurrency. I work in a codebase that heavily uses core.async channels to manage concurrency and you really need to pay close attention to error handling. When you're spawning new threads you need to set up your own custom machinery to re-throw errors on a chans, close chans, and it looks like core.async.flow is a way to do all of this declaratively.
Just like `core.async` itself was a frontrunner of Virtual Threads on the JVM, I view `core.async.flow` as the Clojure version of the upcoming [0]Structured Concurrency JEP. I do wonder if it will use that under the hood once it becomes stable, the same way `core.async` is planning to move away from the `go` macro to just have it dispatch a virtual thread.
[0]https://openjdk.org/jeps/453
For me, the real 'click' moment with core.async wasn't just about replacing callbacks. It was realizing I could model entire business processes as a system of communicating channels. It completely changed how I think about system design.
Curious if you have found any resources to learn more about this way of thinking?
Perhaps this is a good place to start reading: https://en.wikipedia.org/wiki/Communicating_sequential_proce...
Is it like elixir actors
Is Clojure still a thing? I sure would hope so, but I haven't seen much of Clojure activity in HN recently.
The language itself is still getting updates, a new major release was just dropped a month or two ago.
I do find that for about 5 years things seemed to be slowing down. Though I keep seeing it pop up, and new exciting projects seem to pop up from time to time.
Just today I saw an article about Dyna3, a relational programming language for AI and ML that was implemented on top of Clojure.
I miss the Strange Loop conference. I think a lot of Clojure buzz was generated there. Clojure West and a few others so a decent job, but the quality of the talks at Strange Loop were second to none. Not that it was a Clojure specific conference, but it had that focus on elegance that I don't see very often, and the organizer was a something like the Prince of Clojure, if I recall correctly.
I'm still enjoying the language, and all my projects still build and run just fine.
The major frustration I have with the platform is 3D graphics. That's a JVM issue overall though.
To be fair, that is only so much that a Lisp can have as foundation beyond the core forms and macros, especially when it doesn't control the runtime.
Cursive, Calva and CIDER are already quite good.
After that, it is all about the ecosystem, what libraries people care to build.
I just saw a small 3D demo running at 120fps+ that some of the newer JVM vector APIs supposedly enable.
Link to demo @ timestamp: https://youtu.be/UVsevEdYSwI?t=653
My experience with 3D graphics is minimal, but I'm curious to know if these newer developments are significant in any way for 3D work.
I absolutely loved Hickey's talks even when I never used Clojure more than for a few simple examples.
They even invited Guy Lewis Steele, Jr. hos talk is on YouTube and was awesome. His meta-notation is explained more expansively in a paper on his Oracle page.
As others have said, Clojure is still a thing. For anyone catching up with Clojure again after some time: check out Babashka! Think bash scripts, written in Clojure. It's delightful.
https://babashka.org/
I still use it. They finally fixed my biggest complaint about it a year ago, which is that you couldn't use vanilla Clojure lambdas for the Java functional interface, and so you'd have to reify that interface and it was bulky and ugly. Now it works fine so long as the interfaces actually have the @FunctionalInterface attribute.
Not every project uses @FunctionalInterface, but I've been trying to add it to places [1] [2] [3], and now I'm able to use Clojure in a lot more places.
[1] https://github.com/LMAX-Exchange/disruptor/pull/492
[2] https://github.com/apache/kafka/pull/19234
[3] https://github.com/apache/kafka/pull/19366
I sense Clojure attracts a bunch of people that prefers building stuff than talking about building stuff.
It's bad for marketing, but seems promising for the project longevity.
I thought Rich was being a bit pretentious when he compared to violin, but few people ask "are violins still a thing?"
I’d say clojure is very alive and happy. I’m a clojure newb and have been having a super fun time getting into it. Lots of very neat tools are in active development (babashka is the best thing that’s happened to my developer life in a while!!)
The small-medium sized community is actually fantastic for learning. The big names in the community are only a slack away, and everybody is so enthusiastic.
There's more clojure users than ever before and the team is active and afaik larger than ever before.
Things just mature and hype isn't as cool when you heard it 5 years ago.
> Things just mature and hype isn't as cool when you heard it 5 years ago.
which is why now is exactly the right time to start using clojure - after the hype died, but have active community and users.
Is Make still a thing? I sure would hope so, but I haven't seen much of Make activity in HN recently.
I was asking the same question today after investigating XTDB¹ (a Clojure centric bitemporal DB) and went looking for a batteries included WebAssembly framework like Blazor²
1. https://xtdb.com/
2. https://dotnet.microsoft.com/en-us/apps/aspnet/web-apps/blaz...
I'm not sure, but maybe you can use Blazor with ClojureCLR. It's a feature complete Clojure for .net
It is, but the community has been shrinking in recent years.
FWIW, Google Trends shows the hype peaking in 2016, but I doubt that reflects usage as much as buzz.
Instead, if you look at the annual State of Clojure survey results, which solicits opinions directly from the community, the number of responders peaked in 2020 at ~2500, and is down to ~1500 for the most recent 2024 survey.
- 2020 State of Clojure - https://www.surveymonkey.com/results/SM-CDBF7CYT7/
- 2024 State of Clojure - https://www.surveymonkey.com/results/SM-hht04mGydwZ6Nqr7N8vj...
A better source: 2024 survey analysis (and results): https://clojure.org/news/2024/12/02/state-of-clojure-2024
Now... If we are pointing out isolated facts to make an argument, I would caution that survey popularity (sensitive to timing, duration, outreach etc.) is less telling---and less statistically significant---than isolated facts like this:> Clojure versions
> Clojure 1.12.0 was released in September 2024 and the survey showed rapid uptake, with 58% already using it, and 65% developing or deploying with the prior versions 1.11, and a steep drop-off after that. Clojure’s focus on stability and avoiding breaking changes makes upgrades safe and easy.
> Trends (use at work, hobby, and study have all up-trended)
> https://clojure.org/news/2024/12/02/state-of-clojure-2024#tr...
> Because this survey has been running since 2010 (thanks to Chas Emerick originally!), we have lots of great longitudinal data and it’s interesting to compare some of the answers over time.
> Looking at the question of how Clojure developers use Clojure, we can see this has generally trended more towards using it at work. However, this year we saw an uptick of people using it for hobbies or in their studies:
Everything you quoted is based on percentages of the responders, not absolute numbers. Changing in-group proportions don't say anything about overall usage. E.g., if responder work usage goes up 10%, but 40% fewer people use Clojure, that's still a drop in absolute numbers.
Look for the number of responses, and you can see a decline each year after 2020.
---
It's possible that the survey may not have been advertised as well, but afaik, it's still posted the same way it always was: announcements on Clojurians, Clojureverse, reddit, etc. I haven't heard of any reason that survey numbers would have been artificially depressed for several years running.
Very much still a thing. Even on HN: https://hn.algolia.com/?dateRange=all&page=1&prefix=false&qu...
:yes #{of course it is}
This is cool. So basically you create a group of threads and you can treat them as one unit. Trio does something similar (structured concurrency) with async functions for Python. Are these OS threads or green threads?
They can be OS threads or green threads, you can choose.
Are OS threads still the default and you have to pass a virtual thread executor to use virtual threads?
This is really interesting, although I still can't get my head around the fact that core.async.flow topologies are immutable. I feel like most problems can't be solved with fixed topologies.
I guess one could in theory swap flows the same way values are swapped, but I wonder if this is the way this library is supposed to be used. I also wonder what happens to non-empty channel buffers in this case.
I am curious to hear other opinions.
I think LISP is cool and want to use it more but I have 0 appetite to learn the toolchain and debug etc for JVM. You have Racket but Clojure ecosystem is already tiny.
That’s a common misconception. JVM toolchain is way better than the hellscape that are most other language ecosystems. Maven, for example, works reliably and is rock-solid. The only unsolved problem is if you get two libraries/frameworks requesting another dependency, but with different incompatible versions. But I don’t think most other ecosystems solve that painlessly either.
Debug specifically is state-of-the-art. Look at YourKit, or any debugger included with common IDEs.
None of those tools has a shiny Visual 2025 aesthetic, but again, they work reliably and are going to work the same way a year from now.
Indeed, JVM and .NET are the only two major ecosystems out the whole Xerox PARC ideas[0], and the reason that to this day they are my two main workhorses, plus JS runtimes, because Web.
[0] - Technincally Objective-C and Swift could also be considered, but they lack the industry wide adoption, as many cool tools only exist in Apple land.
Leiningen and deps.edn shield you a bit from the awfulness of Java project management. They feel a lot more like something you'd see in Node.js or something, but it still gets dependencies from Maven Central.
Debugging and profiling is still somewhat Java based, and yeah that's can be irritating, but you get used to it.
Personally I do think that it's worth it; Clojure is a very pleasant language that has no business being as fast as it is, and core.async is an absolutely lovely concurrency framework if you can convert your logic into messaging, and you have Haskell-style transactional memory for stuff that can't be. So many problems become less irritating in Clojure.
Is clj-boot still a thing or was it ever a thing?
It or or was a build tool like Leiningen.
Boot seems to have pretty much stalled out. I think the builtin Clojure CLI/deps.edn killed off what momentum it did have.
I've never used clj-boot. I've historically mostly used Leiningen but for the last year or so I finally migrated over to deps.edn.
Clojure taught me lisp where CL failed. Turns out that Scheme and Clojure as a lisp-1 are great for learning.
Switched to SBCL for the faster star-up times. Now lisp-2 also feels more comfortable.
Since you mentioned SBCL, I thought this announcement about ECL and WebAssembly would be worth mentioning for those who are curious. It was announced just last month: https://ecl.common-lisp.dev/posts/Web-ECL-Grant-Announcement... (2025-07-29)
So, kind of the opposite of https://github.com/lovrosdu/klor but with the same goal
I am not sure if this is “opposite” but on the surface looks very interesting!
Funny. I was just thinking about dismissing Clojure for a project I'm going to work on because I was concerned about it's lack of ability to work with async calls. I'm too used to how async in JavaScript and C#, and I'm not sure I'd want to work in an environment that doesn't have a simple way to structure async calls. It doesn't necessarily have to be async / await. Just some attention to the issue rather than completely ignoring it.
That has always been one of Clojure's main strengths (async & concurrency). With the new JVM VirtualThreads, things are looking better than ever.
The transition of core.async specifically to VirtualThreads is still WIP as far as I understand, but with minimal tweaks, 90% of the benefits are already there, even with the current latest version.
Async/await for Clojure: https://github.com/xadecimal/async-style
You can get basically all variations of async coding with Clojure a la carte.
so is this something like core's interpretation of things like ztellman's manifold (https://github.com/clj-commons/manifold)?
EDIT:
gpt says,
Choose core.async.flow when you want a declarative, monitorable process graph over channels (pause/resume, error channel, flow monitor).
Choose Manifold when you need deferreds/streams as general primitives, precise per-op backpressure, error-aware chaining, or you’re in the Aleph/Netty stack.
very abstract but based on this, the answer is no.
typos (from a quick surface scan; I'm not familiar with Clojure or this package):
"The description arity takes the current state ..." should be "The transition arity takes the current state ..."
"excepiton" should be "exception"
"Exceptions thrown from the transition or transform arities, the exception ..." should be "If exceptions are thrown from the transition or transform arities, they ..."
"provded" should be "provided"
See also for related ideas: missionary/electric for frontend and rama for backend. I wish for a unified interface combining the best of all three!
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