I wrote Clojure for about five years. Left when I changed jobs, not because I wanted to. It's genuinely one of the most productive languages I've used, and I still miss the REPL-driven workflow.
One thing I built: defun https://github.com/killme2008/defun -- a macro for defining Clojure functions with pattern matching, Elixir-style. Still probably my favorite thing I've open sourced.
I had an idea about writing something similar, but for multimethods, but never got around thinking it through and trying it out.
The way defmulti and defmethod work is that they do a concurrency safe operation on a data structure, which is used to dispatch to the right method when you call the function.
My hunch is that it should be possible to do something similar by using core match. What I don't know is whether it's a good idea or a terrible one though. When you're already doing pattern matching, then you likely want to see everything in one place like with your library.
AI augmented Repl driven dev has got me back into Clojure and it's been changing my life (full on JVM nerd: Kotlin mostly on the backend).
The syntax is the best in the world (how computer's really operate?) but it's always been a pain to setup the tooling for me. I'm dumb like that. Now with AI it's become super easy to get back into the REPL and I'm in heaven.
Totally moving it back into workflow and proposing to bring it back into the dayjob.
May I ask what your workflow actually looks like? There's been a fair bit of clojureposting over the last few days, and I've decided to jump in and learn.
I love the idea of an AI integrated repl (like what Jeremy Howard and team have done with solveit), it's far more in line with my preferred vision of the AI augmented future of coding. Less "swarm of agent" more, "learn with the agent".
It's good to read that Clojure is getting more and more exposure. I write Clojure fpr my day job and wouldn't want to swap it for anything. The community is small but very helpfull and easy reachable. The learning curve is steap indeed, but very much worth it!
Clojure is easily the most boring, stable language ecosystem I’ve used. The core team is obsessed with the stability of the language, often to the detriment of other language values.
This attitude also exists among library authors to a significant degree. There is a lot of old Clojure code out there that just runs, with no tweaks needed regardless of language version.
Also, you have access to tons of battle tested Java libraries, and the JVM itself is super stable now.
I won’t comment on or argue with your other points, but Clojure has been stable and boring for more than a decade now, in my experience.
What I meant by that is the metaprogramming capabilities that often get cited for allowing devs to create their own domain specific "mini languages". To me that's a "creative" way to write code because the end result could be wildly different depending on who's doing the writing. And creativity invites over-engineering, over-abstraction, and hidden costs. That's what I meant by the "opposite of boring".
You linked me to this comment from another one and I have to agree with this sentiment.
Creating these mini DSLs is something that requires a lot of thought and good design. There is a danger here as you pointed out sharply.
But I have some caveats and counter examples:
I would say the danger is greater when using macros and far less dangerous when using data DSLs. The Clojure community has been moving towards the latter since a while.
There are some _very good_ examples of (data-) DSLs provided by libraries, such as hiccup (and derived libraries), reitit, malli, honeysql, core match, spec and the datalog flavor of Clojure come to mind immediately (there are more that I forget).
In many cases they can even improve performance, because they can optimize what you put into them behind the scenes.
In practice, though, most developers don’t do that.
There’s a rule of thumb: write a macro as a last resort.
It’s not hard to stick to it. In general, you can go a long, long way with HOFs, transducers, and standard macros before a hand-rolled macro would serve you better.
> syntax is hard to read unless you spend a lot time getting used to it
That’s pretty much exactly the opposite of how I always felt. Perhaps because I’m not a programmer by education, I always struggle to remember the syntax of programming languages, unless I’m working in them all the time. After I return to a language after working in other languages for a while, I always have difficulties remembering the syntax, and I spend some time feeling very frustrated.
Clojure and Lisps more generally are the exception. There is very little syntax, and therefore nothing to remember. I can pick it up and feel at home immediately, no matter how long I’ve been away from the language.
The JVM is one of the major selling points of Clojure. You can "write once, run anywhere" and benefit from Java's massive ecosystem, all without having to use a Blub language. Modern JVM implementations are also incredibly fast, often comparable in performance to C++ and Go.
It's almost as if different tools exist for solving different problems. Clojure is "Lisp on the JVM". That's the core premise behind the language. Rust is a "systems programming language with a focus on type and memory safety". This is an apples-to-oranges comparison. They offer different benefits while providing different drawbacks in return. Their ecosystems are likewise very different, in each case more closely tailored to their particular niche.
I am a Clojure fan and would love to use it. But you are right, we live in a real world where money talks and most organizations want to see developers as cheap, replaceable commodities.
Not to mention in a post AI world, cost of code generation is cheap, so orgs even need even fewer devs, combine all this with commonly used languages and frameworks and you need not worry about - "too valuable to replace or fire".
Having said that - there may be a (very) small percentage of orgs which care about people, code crafting and quality and may look at Clojure as a good option.
"The TIOBE index measures how many Internet pages exist for a particular programming language."
For some reason I doubt this is in any way representative of the real world. Scratch, which is a teaching language for children, bigger than PHP? Which is smaller than Rust? Yeah, these are results you get when you look at the Internet, alright.
Sure that index isn't great (I think it's basically a regurgitation of Google Trends), but I don't think you're suggesting Clojure is actually a popular language are you? Which is the only point I'm trying to make (that it isn't popular).
Clojure is reasonably popular as far as programming languages go. It's not difficult to get a job as a Clojure developer, particularly in certain sectors (fintech and healthcare are the heaviest Clojure users). Of course C++, Java, C# and PHP dwarf both Clojure and Rust by several orders of magnitude.
If anything, I think that makes Clojure better. Almost no one in the community is doing stuff to serve "lowest common denominator", compared to how most of JS/TS development is being done, which is a breeze of fresh air for more senior programmers.
Besides, the community and ecosystem is large enough that there are multiple online spaces for you to get help, and personally I've been a "professional" (employed + freelancing) Clojure/Script developer for close to 7 years now, never had any issues finding new gigs or positions, also never had issues hiring for Clojure projects either.
Sometimes "big enough" is just that, big enough :)
I'm glad it works for you and many others and gives you a good living. Nothing wrong with that. I wasn't trying to attack it or anyone that uses it, just stating why I never warmed up to it and projecting why I think it hasn't become popular.
That's fair if you're looking at it from a performance perspective.
Not entirely fair if you look at it from a perspective of wanting fast feedback loops and correctness. In Clojure you get the former via the REPL workflow and the latter through various other means that in many cases go beyond what a typical type system provides.
> the opposite of boring
It's perhaps one of the most "boring in a good way" languages I ever used.
> - syntax is hard to read unless you spend a lot time getting used to it
This is only true if you assume C-like syntax is the "default."
But regardless of that, I'd argue that there's much less syntax to learn in LISPy languages. The core of it is really just one single syntactic concept.
It's repeated a lot because it's true. The collective developer world has decided that LISP syntax is not the preference. Good if you prefer it, but you're the in the overwhelming minority.
Slightly off topic, but I find it to be a testament of how software has already eaten the world when friggin Michelin has a tech blog. What's next? General Electric releasing a frontend framework?
I'd love to work with Clojure. I have the misfortune of working on something that is stuck on java1.8 and Groovy, part of the issue is the code quality is a disaster (json and xml parsed with regex...). At least with Clojure I'd get to enjoy the repl workflow and usable text editor (emacs). I also just enjoy working with sexps.
Honestly, if I could quit my job for six months and work in a codebase like yours, I'm extremely curious what I could accomplish with AI.
We have a codebase at work that was "stuck." We've consistently done minor library upgrades, but no major upgrades in several years, and was recognized as a major piece of technical debt / minor disaster for almost two years, in that we urgently needed to dedicate an engineer to it for a month or more to bring it up to date. We also suspected that framework upgrades would improve performance enough to save us a little bit in operating costs. I got curious, created a branch, and threw Claude at it. Claude knocked it out in a couple of days while I mostly worked on other things. Then we dedicated several engineer days to doing extra manual testing. Done and deployed. Now we're ready to experiment with giving it less resources to see if the performance improvement holds up in practice.
This codebase was only about 200k lines of code, so probably smaller than yours. Really curious how it would go with a larger codebase.
EDIT: Claude may only have taken a couple of days because I was only checking in occasionally to give it further instructions. I don't know how fast it would have been with my complete attention.
simplest way to think about it: the python repl is a scratch pad next to your code. the clojure repl IS your running application. you're rewiring the plane mid-flight instead of landing, making changes, and taking off again. once you experience that feedback loop you genuinely can't go back.
Almost exactly, it's mostly how you use the REPL that differs, and then only because of what different editors prioritise. When I'm in Emacs, all my work happens against a running REPL - when I open or save a file, it's reloaded. Any tests loaded in the REPL rerun on every save, within that live instance. If I drop into the debugger, it's against that live instance. I can swap in mock components to a running system, go check stuff in a browser (even jack into a live webpage with ClojureScript), all in one long running instance. I have struggled to recreate this kind of setup as smoothly in Python with any editor (pytest doesn't want to run this way, and IPython's autoreload doesn't feel as reliable), but I do probably write more REPLy code in Python than most, so all my model training and optimisation runs during development happen in pausable background threads in IPython etc.
All that said, 90% of the time you still just eval a bit of a code to see what happens and that's the same between the two languages.
An example of me solving an Advent of Code with clojure and repl. You can see i never interact with the repl directly, I just send code to it via my editor and get results inline.
You evaulate code within your editor against the REPL, seeing the output in the same window you're writing in (perhaps in a different buffer).
The cycle is:
1. Write production code.
2. Write some dummy code in the same file (fake data, setup).
3. Evaluate that dummy code. See what happens.
4. Modify code until satisfied.
Your feedback loop is now single digit seconds, without context switching. It's extremely relaxing compared to the alternatives (rerunning tests, launching the program with flags, what have you).
Indeed. For people used to the "typical REPL" from Ruby, Python and alike, the best comparison I've found is this:
"Typical REPL" workflow: Have one editor open, have one REPL open, have one terminal open that runs the application. One change is typically: Experiment in the REPL window, copy-paste into your editor, write tests, restart application (lose all state), setup reproduction state, test change. Or something like this.
In a Clojure REPL workflow, you'd do something like: Have one editor open, this starts the REPL and often the application in the background too. One change is typically: Edit code, evaluate that snippet of code (which sends it to the REPL and the running application), write tests, evaluate them too in the editor, if you're happy, hit CTRL+S and you're done. Application still has the existing state, no restarts needed and you essentially never have to leave the editor window/pane.
Of course, others might have slightly different workflows, but for myself and many (most?) other Clojure developers I've observed in the wild, this is pretty much the standard.
You're on to something. It's the lisp machine of it all. Hot reloading is nothing that requires anything special, so you can redefine a callback or dependency with ease in the repl and the system chugs along. You can theoretically do something similar in ruby, but it's the opposite of elegant, you'd be forced to re implement methods with different dependencies etc. It's also a function of being "functional" in the lisp sense, that things are lists, and lists can be replaced, functions or otherwise.
The fun way to get a feel for lisp machines is emacs, it's so easy to fall of a language and especially hand-coding in a language if you don't have to.
More or less, yes. It's more about the approach to the repl and how it is leveraged in development, or even jacking in to a running system and modifying it as it is running.
I wrote Clojure for about five years. Left when I changed jobs, not because I wanted to. It's genuinely one of the most productive languages I've used, and I still miss the REPL-driven workflow.
One thing I built: defun https://github.com/killme2008/defun -- a macro for defining Clojure functions with pattern matching, Elixir-style. Still probably my favorite thing I've open sourced.
I like it! Really nice API.
I had an idea about writing something similar, but for multimethods, but never got around thinking it through and trying it out.
The way defmulti and defmethod work is that they do a concurrency safe operation on a data structure, which is used to dispatch to the right method when you call the function.
My hunch is that it should be possible to do something similar by using core match. What I don't know is whether it's a good idea or a terrible one though. When you're already doing pattern matching, then you likely want to see everything in one place like with your library.
AI augmented Repl driven dev has got me back into Clojure and it's been changing my life (full on JVM nerd: Kotlin mostly on the backend).
The syntax is the best in the world (how computer's really operate?) but it's always been a pain to setup the tooling for me. I'm dumb like that. Now with AI it's become super easy to get back into the REPL and I'm in heaven.
Totally moving it back into workflow and proposing to bring it back into the dayjob.
> how computer's really operate?
I don't know exactly what you mean by this, but Clojure syntax is not really anywhere close to how computers actually process instructions.
Clojure is very nice though.
May I ask what your workflow actually looks like? There's been a fair bit of clojureposting over the last few days, and I've decided to jump in and learn.
I love the idea of an AI integrated repl (like what Jeremy Howard and team have done with solveit), it's far more in line with my preferred vision of the AI augmented future of coding. Less "swarm of agent" more, "learn with the agent".
Also I love your take.
Feel like a holy grail to me to back in the hot seat with repl driven but I can drop in and figure things out... all on the JVM. Madness!
It's good to read that Clojure is getting more and more exposure. I write Clojure fpr my day job and wouldn't want to swap it for anything. The community is small but very helpfull and easy reachable. The learning curve is steap indeed, but very much worth it!
Clojure has some pretty big downsides last i looked:
- syntax is hard to read unless you spend a lot time getting used to it
- convention for short var names makes it even harder
- function definition order makes it even harder
- too dynamic for most people's taste
- no type safety
- the opposite of boring
- no clear use case to show it clearly beating other languages
- niche with small community and job market
- JVM
For all those reasons its a hard sell for most imo.
> the opposite of boring
I have to push back on this one, respectfully.
Clojure is easily the most boring, stable language ecosystem I’ve used. The core team is obsessed with the stability of the language, often to the detriment of other language values.
This attitude also exists among library authors to a significant degree. There is a lot of old Clojure code out there that just runs, with no tweaks needed regardless of language version.
Also, you have access to tons of battle tested Java libraries, and the JVM itself is super stable now.
I won’t comment on or argue with your other points, but Clojure has been stable and boring for more than a decade now, in my experience.
What I meant by that is the metaprogramming capabilities that often get cited for allowing devs to create their own domain specific "mini languages". To me that's a "creative" way to write code because the end result could be wildly different depending on who's doing the writing. And creativity invites over-engineering, over-abstraction, and hidden costs. That's what I meant by the "opposite of boring".
You linked me to this comment from another one and I have to agree with this sentiment.
Creating these mini DSLs is something that requires a lot of thought and good design. There is a danger here as you pointed out sharply.
But I have some caveats and counter examples:
I would say the danger is greater when using macros and far less dangerous when using data DSLs. The Clojure community has been moving towards the latter since a while.
There are some _very good_ examples of (data-) DSLs provided by libraries, such as hiccup (and derived libraries), reitit, malli, honeysql, core match, spec and the datalog flavor of Clojure come to mind immediately (there are more that I forget).
In many cases they can even improve performance, because they can optimize what you put into them behind the scenes.
I read comments like these in bewilderment.
Have you worked for a company that hasn’t created its own, as you put it “mini language”?
Have you worked for a company that doesn’t indulge in over engineering, over abstraction and hidden cost?
Do you actually do programming for a job at all?
speaking of bewilderment, i'm not sure at all what you're getting at here.
because programmers suck we should make tools that make it easier for them to suck?
In practice, though, most developers don’t do that.
There’s a rule of thumb: write a macro as a last resort.
It’s not hard to stick to it. In general, you can go a long, long way with HOFs, transducers, and standard macros before a hand-rolled macro would serve you better.
> syntax is hard to read unless you spend a lot time getting used to it
That’s pretty much exactly the opposite of how I always felt. Perhaps because I’m not a programmer by education, I always struggle to remember the syntax of programming languages, unless I’m working in them all the time. After I return to a language after working in other languages for a while, I always have difficulties remembering the syntax, and I spend some time feeling very frustrated.
Clojure and Lisps more generally are the exception. There is very little syntax, and therefore nothing to remember. I can pick it up and feel at home immediately, no matter how long I’ve been away from the language.
The JVM is one of the major selling points of Clojure. You can "write once, run anywhere" and benefit from Java's massive ecosystem, all without having to use a Blub language. Modern JVM implementations are also incredibly fast, often comparable in performance to C++ and Go.
i don't think you're wrong necessarily...but rust, golang, zig, mojo, etc are gaining popularity and imo they wouldn't be if they were JVM languages.
It's almost as if different tools exist for solving different problems. Clojure is "Lisp on the JVM". That's the core premise behind the language. Rust is a "systems programming language with a focus on type and memory safety". This is an apples-to-oranges comparison. They offer different benefits while providing different drawbacks in return. Their ecosystems are likewise very different, in each case more closely tailored to their particular niche.
understood, i'm just pointing out that people seem to prefer the apple over the orange.
I am a Clojure fan and would love to use it. But you are right, we live in a real world where money talks and most organizations want to see developers as cheap, replaceable commodities.
Not to mention in a post AI world, cost of code generation is cheap, so orgs even need even fewer devs, combine all this with commonly used languages and frameworks and you need not worry about - "too valuable to replace or fire".
Having said that - there may be a (very) small percentage of orgs which care about people, code crafting and quality and may look at Clojure as a good option.
Most of those seem very subjective with many people having the exact opposite opinion.
yes it's just my opinion. but Clojure's market share is tiny so there must be something to that.
it's not even in the top 50 here: https://www.tiobe.com/tiobe-index/. Lisp is 26.
"The TIOBE index measures how many Internet pages exist for a particular programming language."
For some reason I doubt this is in any way representative of the real world. Scratch, which is a teaching language for children, bigger than PHP? Which is smaller than Rust? Yeah, these are results you get when you look at the Internet, alright.
Sure that index isn't great (I think it's basically a regurgitation of Google Trends), but I don't think you're suggesting Clojure is actually a popular language are you? Which is the only point I'm trying to make (that it isn't popular).
Clojure is reasonably popular as far as programming languages go. It's not difficult to get a job as a Clojure developer, particularly in certain sectors (fintech and healthcare are the heaviest Clojure users). Of course C++, Java, C# and PHP dwarf both Clojure and Rust by several orders of magnitude.
If anything, I think that makes Clojure better. Almost no one in the community is doing stuff to serve "lowest common denominator", compared to how most of JS/TS development is being done, which is a breeze of fresh air for more senior programmers.
Besides, the community and ecosystem is large enough that there are multiple online spaces for you to get help, and personally I've been a "professional" (employed + freelancing) Clojure/Script developer for close to 7 years now, never had any issues finding new gigs or positions, also never had issues hiring for Clojure projects either.
Sometimes "big enough" is just that, big enough :)
I'm glad it works for you and many others and gives you a good living. Nothing wrong with that. I wasn't trying to attack it or anyone that uses it, just stating why I never warmed up to it and projecting why I think it hasn't become popular.
JVM + Syntax is upside for me.
Type's are for compilers ;) jk. I'm fully lover or type's but removing the constraint is easy in clojure. teams resist.
<3 the opposite of boring.
> no type safety
That's fair if you're looking at it from a performance perspective.
Not entirely fair if you look at it from a perspective of wanting fast feedback loops and correctness. In Clojure you get the former via the REPL workflow and the latter through various other means that in many cases go beyond what a typical type system provides.
> the opposite of boring
It's perhaps one of the most "boring in a good way" languages I ever used.
> It's perhaps one of the most "boring in a good way" languages I ever used.
this is what i meant by that: https://news.ycombinator.com/item?id=47614353
> - syntax is hard to read unless you spend a lot time getting used to it
This is only true if you assume C-like syntax is the "default."
But regardless of that, I'd argue that there's much less syntax to learn in LISPy languages. The core of it is really just one single syntactic concept.
This guy gets it.
The syntax argument is such a tired argument. With LISPy language there is almost zero syntax, it's pretty much executable AST.
Because of this, formatting matters a lot, but I don't think that's too different than other languages.
If you think LISP is hard to read, you are someone who could most benefit from branching out to a non-Algol lineage language.
Also, the little syntax present is pretty much timeless. Learn once and its yours for the next 50 years.
> The syntax argument is such a tired argument.
It's repeated a lot because it's true. The collective developer world has decided that LISP syntax is not the preference. Good if you prefer it, but you're the in the overwhelming minority.
Random example i just found via github explore: https://github.com/replikativ/datahike/blob/main/src/datahik...
You probably love it but to me it looks like a wall of text. Sure I can figure out what it does, but it gives me a headache.
Moby Dick is too hard to read. They should make it shorter with a limited vocabulary.
I kinda get where you're trying to go, but is Moby Dick style writing the best way to convey information?
That is, prose is good for entertainment, but less so for conveying information, even less so for exactness.
Point being that things of high quality that are enriching sometimes require an investment
Slightly off topic, but I find it to be a testament of how software has already eaten the world when friggin Michelin has a tech blog. What's next? General Electric releasing a frontend framework?
Toyota has an open source game engine written in Flutter!
https://www.youtube.com/watch?v=98n32VstnpI
> general electric releasing a frontend framework
or toyota releasing a game engine: https://www.theverge.com/games/875995/toyota-fluorite-game-e...
You'd be surprised: https://www.ethosdesignsystem.com/
(okay it's a design system, not so much a framework, but still)
Funny example since they’re known for automotive parts and their food guide. It’s almost on brand.
I mean how else are you going to get people to drive long distances and buy more tires without giving them yummy destinations to eat at?
I'd love to work with Clojure. I have the misfortune of working on something that is stuck on java1.8 and Groovy, part of the issue is the code quality is a disaster (json and xml parsed with regex...). At least with Clojure I'd get to enjoy the repl workflow and usable text editor (emacs). I also just enjoy working with sexps.
Honestly, if I could quit my job for six months and work in a codebase like yours, I'm extremely curious what I could accomplish with AI.
We have a codebase at work that was "stuck." We've consistently done minor library upgrades, but no major upgrades in several years, and was recognized as a major piece of technical debt / minor disaster for almost two years, in that we urgently needed to dedicate an engineer to it for a month or more to bring it up to date. We also suspected that framework upgrades would improve performance enough to save us a little bit in operating costs. I got curious, created a branch, and threw Claude at it. Claude knocked it out in a couple of days while I mostly worked on other things. Then we dedicated several engineer days to doing extra manual testing. Done and deployed. Now we're ready to experiment with giving it less resources to see if the performance improvement holds up in practice.
This codebase was only about 200k lines of code, so probably smaller than yours. Really curious how it would go with a larger codebase.
EDIT: Claude may only have taken a couple of days because I was only checking in occasionally to give it further instructions. I don't know how fast it would have been with my complete attention.
every time i go back to writing non-clojure code outside of repl-driven environment i feel like a cave man banging rocks against each other
no amount of ide smartness or agentic shenanigans is going to replace the feeling of having development process in sync with your thought process
You just made me wonder if REPL driven development and LLMs can be better combined somehow.
This is already a strong theme in the Clojure ecosystem, e.g.:
https://github.com/BetterThanTomorrow/calva-backseat-driver
Can someone enlighten me about the REPL that lispers keep raving about? Isn't it more-or-less the same as the Python REPL?
simplest way to think about it: the python repl is a scratch pad next to your code. the clojure repl IS your running application. you're rewiring the plane mid-flight instead of landing, making changes, and taking off again. once you experience that feedback loop you genuinely can't go back.
Almost exactly, it's mostly how you use the REPL that differs, and then only because of what different editors prioritise. When I'm in Emacs, all my work happens against a running REPL - when I open or save a file, it's reloaded. Any tests loaded in the REPL rerun on every save, within that live instance. If I drop into the debugger, it's against that live instance. I can swap in mock components to a running system, go check stuff in a browser (even jack into a live webpage with ClojureScript), all in one long running instance. I have struggled to recreate this kind of setup as smoothly in Python with any editor (pytest doesn't want to run this way, and IPython's autoreload doesn't feel as reliable), but I do probably write more REPLy code in Python than most, so all my model training and optimisation runs during development happen in pausable background threads in IPython etc.
All that said, 90% of the time you still just eval a bit of a code to see what happens and that's the same between the two languages.
The two big things are:
1. REPL is automatically compiled into running systems 2. Great hot-reloading support
So it's generally very easy to "poke" at a running system, and the whole dev process assumes you will do this.
TBH, these days it is largely possible in a C++ debugger. Less so 10 years ago, though.
https://www.youtube.com/watch?v=5HHLT2_a1tI
An example of me solving an Advent of Code with clojure and repl. You can see i never interact with the repl directly, I just send code to it via my editor and get results inline.
You evaulate code within your editor against the REPL, seeing the output in the same window you're writing in (perhaps in a different buffer).
The cycle is:
Your feedback loop is now single digit seconds, without context switching. It's extremely relaxing compared to the alternatives (rerunning tests, launching the program with flags, what have you).Indeed. For people used to the "typical REPL" from Ruby, Python and alike, the best comparison I've found is this:
"Typical REPL" workflow: Have one editor open, have one REPL open, have one terminal open that runs the application. One change is typically: Experiment in the REPL window, copy-paste into your editor, write tests, restart application (lose all state), setup reproduction state, test change. Or something like this.
In a Clojure REPL workflow, you'd do something like: Have one editor open, this starts the REPL and often the application in the background too. One change is typically: Edit code, evaluate that snippet of code (which sends it to the REPL and the running application), write tests, evaluate them too in the editor, if you're happy, hit CTRL+S and you're done. Application still has the existing state, no restarts needed and you essentially never have to leave the editor window/pane.
Of course, others might have slightly different workflows, but for myself and many (most?) other Clojure developers I've observed in the wild, this is pretty much the standard.
Being someone who’s used to the “typical REPL” flow, I’m not sure I grasp what’s going on with the no-restarts. The implications I think I see are:
* Clojure is built different in terms of hot code reloading
* the REPL is its own application process in languages Ruby or Python, but in Clojure it’s sortof a client for the system
Is that right? Is there more to it?
You're on to something. It's the lisp machine of it all. Hot reloading is nothing that requires anything special, so you can redefine a callback or dependency with ease in the repl and the system chugs along. You can theoretically do something similar in ruby, but it's the opposite of elegant, you'd be forced to re implement methods with different dependencies etc. It's also a function of being "functional" in the lisp sense, that things are lists, and lists can be replaced, functions or otherwise.
The fun way to get a feel for lisp machines is emacs, it's so easy to fall of a language and especially hand-coding in a language if you don't have to.
Is this similar to Unison scratch file driven development?
it is very similar, but it is easier to evaluate sub-expressions thanks to the unique syntax of lisp.
there's a detailed explanation here: https://youtu.be/Djsg33AN7CU?t=659
More or less, yes. It's more about the approach to the repl and how it is leveraged in development, or even jacking in to a running system and modifying it as it is running.
https://archive.ph/5RJ2V
What is the y axis in first chart? What is the data source?
They publish their yearly surveys on their official website. The graph seems to be from State of Clojure 2020:
https://clojure.org/news/2020/02/20/state-of-clojure-2020
The most recent report:
https://clojure.org/news/2026/02/18/state-of-clojure-2025
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