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Comment by labrador | Hacker News Reader

It occurred to me this morning that I should learn Clojure instead of Rust for non-lowlevel code because Clojure solves the same problems Rust solves in a much simpler way. I'm a fan of Clojure author Rich Hickey's "Simple Made Easy" talk but otherwise don't know either language in detail and need to do more research.

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The Clojure (or any Lisp) journey is very different, not because of the language per se, but because of the developer experience.

In Clojure, there's no appreciable compilation time. During my work week I barely, if ever, restart the application I'm working on: I'm working inside of it via a REPL connection.

It's an entirely different ball game and if you just compare language features you are missing out on an incredible interactive coding experience.

Does it scroll? Because I like to scroll around when thinking about my program. I always imagine Lips REPL ppl saying they keep the entire program in their head but that can't be right. That's doing things the hard way.

You have files and editors for your files, eg emacs or vim or vscode.

Your editor is also directly connected to your running application and can compile individual functions or pieces of code to update the application without a full edit/compile/run/test loop. It happens way faster and more interactively while you code. You can directly inspect the running program and its data within that same framework and with the exact same tools and functions you use to code.

To answer another way, you don’t code your application in a REPL, like by line , but with all the tools you’d expect (editor or ide, git, etc) PLUS that live connection to your software.

The nice thing about REPLs is that you can try random snippets code. And as the sibling comments put it, you rarely switch to the prompt interface. Instead you `eval` a bit of code and it got sent to the running state of your program as if you've typed it as the prompt. It's more like brainstorming a program using a mood board.

You kinda have to keep track of the state, but the latter can be easily inspected so there's no need to keep it your head.

I'd even say it gives you an incentive to not keep a lot of opaque state lying around and this is a good thing

You tell your editor to evaluate any arbitrary part of the source file you currently have open, and it does so in the context of your running application without stopping it.

Then you see the result in another pane of your editor.

It's pretty revelatory. You're molding your program while it's running.

Can confirm! Once I started doing this (now mainly with iPython interactive in VSCode) my output speed increased dramatically

To note that the same experience is shared with Smalltalk, and modern IDEs still are lacking of both.

> Clojure solves the same problems Rust solves in a much simpler way

I'm curious about that, can you elaborate? I'm a beginner in Clojure and I only know a few concepts about Rust, but it seems to me that they solve (at least, currently) very different problems...

I only saw Rust being used in places where C or C++ would be used in the past (Linux kernel, CLI apps, desktop apps), while I only saw Clojure being used as a modern and functional Java and JS replacement.

Not to mention how different they are as languages (static vs dynamic typing, native vs jvm, borrow checker vs garbage collection)

One thing that jumped out at me is you don't need Rust's borrow checker to prevent thread race conditions because data in Clojure is immutable. That's a huge simplification over Rust. What I hear mostly about Rust is complaints about the borrow checker. I wrote a simple Rust utility and found it frustrating. But again, don't take my word for it because I don't know either language.

I would argue that F# would be the choice of language in place of Rust if you don't want to deal with Rust's type system. F# is immutable by default with good concurrency and a static type system.

That's a great suggestion I had forgotten about, which is strange since I'm a C# programmer. Part of me wants to really learn a Lisp to see what it is special about it that I keep hearing about. I tried Racket and Steel Bank Common Lisp but they didn't seem appropriate for the commercial programming I'm used to. Clojure is being used commercially.

I also really like Lisps/Schemes. I've always wanted to pick up Clojure but don't like how it thinly sits on top of the JVM compared to F# being deeply integrated. I always had trouble getting Clojure properly installed compared to just downloading .NET and having F# or easily downloading Racket.

You should absolutely try out F#. :) It's a great language.

Also, if you're looking for the magic of Lisp/Scheme, I think you might really enjoy Elixir/Erlang. Elixir has macros, has purely immutable data (there is _no_ way whatsoever to get mutable data unlike F#, Racket, Clojure, etc.), live code updates, and the BEAM VM, its process framework, and OTP are quite magical.

When I first learned Erlang, I felt I had come home. I mainly used Elixir though due to the available packages and jobs.

The late great Joe Armstrong is missed! Good suggestion, I will take a look at Elixer/Erlang. It's the least I can do for the laughs Joe gave me in his videos.

Shameless plug if you like videos: I gave a talk about Erlang, building the language (focus on semantics, not syntax) up from the fact that the = sign doubles as a runtime assertion.

https://youtu.be/E18shi1qIHU

Joe was indeed a great guy. I was lucky enough to spend some private time with him when he was visiting Chicago to give a talk, a true renaissance man with wide-ranging interests.

Good talk! I didn't believe that Go example was real at first. A bit strange. I always think of Alan Kay's message passing objects when listening to descriptions of Erlang and tonight I also thought about Kubernetes pods. The other thought is one you touched on is that some systems are monolithic so you have to handle errors. Thanks, I enjoyed that.

This would be the Elixir talk I'd watch to get excited about it: https://youtu.be/JvBT4XBdoUE

As someone who has gone deep into both functional programming (with Elixir, Clojure, and Scala) and also Rust, they solve the same problem in different ways with different tradeoffs.

The problem is that shared mutable state is incredibly hard to get correct, especially when concurrency enters the picture.

Elixir and Clojure sidestep the problem by making copying data so cheap that instead of sharing references to mutable data, you make all data immutable and copy it whenever you want to change it in some way. (Which is a classic technique: don’t like the problem? Solve a different problem that sidesteps the original problem in a creative way)

So you have a lot of functions of roughly the shape `f -> f` (return a new thing) instead of `f -> ()` (mutate a thing in place).

This possible at all by the clever use of some novel data immutable structures like HAMTs that are able to approximate the performance of traditional mutable data structures like hashmaps or arrays while presenting an immutable API.

As it turns out, this is a much easier programming model for most of us to get correct in practice (especially in the presence of concurrency) than sharing mutable state in an imperative programming language like C or Java or Python.

The tradeoff is that the immutable functional data structures actually do have a some performance overhead. In most domains it's not large enough to matter, but in some domains it is, and in those domains you really do need mutable state to eek out that last bit of performance.

Which is where Rust comes in.

In Rust's model, data can either mutable or shared, but not both at the same time. The Rust compiler computes the lifetimes of data throughout your program to ensure that this invariant is upheld, so mutable data is not shared, and shared data is not mutated.

The downside of this is that you have to internalize these rules and program to them. They can be tough to learn and tough to program with even after you have learned them, though it does get much easier with experience, I will say.

The upside of Rust's model is that you can have your cake and eat it too: you can keep the high performance ceiling of a true mutable data model while maintaining memory and resource safety.

In short, you can think of Clojure/Elixir as sidestepping the shared mutability problem at the cost of some runtime performance (though again in practice it is smaller than you would think), and Rust as tackling the shared mutability problem head on by transferring the cost of solving the problem to a more complicated compiler and a harder-to-learn programming model.

These are just my opinions having used both Rust and the immutable data functional programming stuff in anger. I'm not trying to present one as being better than the other, the key point is that they're both better than what came before.

My read today is that the advantage of Rust over C/C++ is that the compiler enforces the rules, where in C/C++ you'd have to use a static source code analyzer to find omissions. Since Clojure uses Software Transactional Memory and Persistant Data Structures to only make copies of updated shared data structures, it seems like it could actually be faster than Rust/C/C++ depending on how efficient the copy is. I may have it wrong but it sure is interesting...

That’s my take after using Rust for half a decade. The type system is very powerful and can encode logic in types in a way that’s impossible in most other languages, which is how the borrow checker works (the lifetime of a reference is part of its type).

> can encode logic in types in a way that’s impossible in most other languages

It’d be of great help if you could share an example of this along with an explanation why it’s impossible in a different language say one of Java/C++/Go

While STM was a big selling point when Clojure in practice it's actually very rarely used. The persistent data structures are indeed the heart of Clojure.

While for many applications Clojure's performance is good enough it's not anywhere near what you can achieve with Rust. I once did a small game in Clojure trying to be very clever to eke out every last bit of performance and still didn't hit an acceptable frame rate. Made a very naive reimplementation in Rust that involved copying the entire state every frame and it run buttery smooth.

If there is a task for wish persistent data structures are the most performant solution it should be easy enough to implement and use them in rust too. Probably someone already did that.

Clojure is my default programming language but if I want performance (or static types) I reach for Rust.

> in C/C++ you'd have to use a static source code analyzer to find omissions

Clang and GCC have a pretty solid suite of static checks that they can enforce if you enable them. They catch most of the common footguns.

It's worth noting that there's several implementations of persistent/immutable/functional data structures for Rust already, and a few basic "building blocks" (namely std::borrow::Cow, noted for its bovine superpowers) are even in the Rust standard library. It's possible that we'll see more of them standardized in the future if a case can be made that they're useful and a consensus is reached wrt. some kind of minimally viable APIs.

Did you look into zig and their solution ?

The main problem that Rust tries to solve, and that functional programming (which Clojure heavily leans into) solves, is avoiding shared mutable state, which leads to data races and (potentially subtly) wrong concurrent programs. Functional programming avoids shared mutable state by avoiding mutable state. Operations are only represented as transformations instead of mutations. Other languages like Erlang / Elixir use message passing techniques like the Actor Model to avoid shared mutability. Instead of avoiding mutability, like in functional programming, in the Actor Model you avoid sharing, by instead sending messages around.

Rust is interesting because it solves the problem of shared mutable state, while allowing sharing, and allowing mutability, just not at the same time. State can be mutated until it is shared. While it is shared, it cannot be mutated. This is the goal of the ownership system in Rust.

> The main problem that Rust tries to solve, and that functional programming (which Clojure heavily leans into) solves, is avoiding shared mutable state

I would argue that avoiding _unrestricted_ shared mutable state is a mean for Rust, not a goal. The main goal would be to provide a way to make safe, fast and non garbage collected programs, which doesn't seem at all what clojure is aiming for.

As proven by ongoing research in things like Linear Haskell, one doesn't need to throw GC productiviy away, to get deterministic resource management.

Best part of Rust is catering to a crowd that not even at point gun will consider touching anything that might resemble having any kind of automatic resource management.

Hence why I consider articles like "How We Saved 70% of CPU and 60% of Memory in Refinery’s Go Code, No Rust Required" [0] interesting to read and make awareness, even if Go isn't one of the languages I happen to be entusiastic about.

[0] - https://www.honeycomb.io/blog/how-we-saved-70-cpu-60-memory-...

Well, erlang and elixir operate on almost exclusively immutable data, in addition to message passing between "processes". They are more strict than most other languages in that regard.

Mutation occurs at the actor level. Their state is mutated by changing how they respond to future messages.

This the “non-low level” code qualification.

As an anecdote, about a year ago I realized I was not having that much fun learning rust. Randomly landed on clojure instead and have absolutely loved it.

Particularly as a noob, babashka is SUCH a good way to learn the language. I’ve written myself all sorts of fun utilities with babashka and have learned so much clojure along the way. Even got my coworkers to use my bb scripts!

I would recommend taking a look at some of the schemes. In particular I've been having tons of fun with CHICKEN: https://call-cc.org/ - the fact that it compiles to C and can generate binaries is a great plus.

I have been enjoying Chez scheme these last few weeks, and having an LLM has helped me when i have missing libraries. The ability to just wrap a C library and statically link everything into a single binary has been really nice too!

Clojure is a niche language that (for realistic purposes) is still tied to a single platform, the JVM, which (Clojure, not the JVM) looks more dead with every passing year. It never became popular and it's been steadily losing users. It's also not as general purpose as Common Lisp (ie. not suited for system or lowlevel programming).

If you're going to learn a niche Lisp, you might as well learn Common Lisp or Scheme which have well-specified standards, have stood the test of time and will still be around for decades to come.

> the JVM, which looks more dead with every passing year.

Lol, only dying/dead in the febrile imagination of some HN commenters. The JVM has had some of the most explosive feature activity in the last several years. Java had several million greenfield projects in 2024-25 - among the top 6 greenfield programming languages according to the Github Octoverse.

But also: https://survey.stackoverflow.co/2024/work#3-salary-and-exper...

Prolog and Dart programmers earn the least, but Erlang and Clojure programmers earn the most? Something is fishy here...

I would take this statistics, like every other one, with a grain of salt, but still wanted to put it out there as a possible discussion point.

Likely just not a statistically significant enough sample of any of those to justify them even putting them on the chart. Except maybe Dart, and that gets the "curse" of being front-end tech which for some inexplicable reason is underpaid.

Yeah, that seems likely. Although it's lower than PHP!

>>Clojure programmers earn the most?

All the best finding a Clojure job though.

Im guessing they pay all that much, while simultaneously cursing themselves for not using Python instead, and swearing to never use Clojure again.

I know that as I have seen people do and say similar things about Perl and Erlang in the last decade.

Nope. I mostly happily used Python in my previous job for many years, now I'm doing Clojure. There are benefits and drawbacks to each, but I don't know if I'd want to go back to Python. I'm a Lisper (Schemer, really) at heart so maybe I'm biased.

Having said that, I don't think I'd pick Clojure for unpaid (hobby) projects. The JVM is such a hog and I don't like anything related to the Java culture...

I suspect kamaal meant that the people who hired you are cursing themselves for making such an expensive decision.

I prefer CL, but… clojure at least has some commercial usage and is by far the most successful of current lisps, if we do not count elisp.

Just to counter-balance the inferred conclusion that Common Lisp would not have any commercial usage (sorry, words are important, FUD is too close from hasty wording or hasty conclusions): https://github.com/azzamsa/awesome-lisp-companies/ (example companies using CL today, and yes some pick it for new projects, and yes some hire) (and I don't want to argue if the list is impressive or not: it's some commercial usage :D best,)

Clojure will be around as long as the jvm. It’s mostly done at the core level, most updates are to leverage new host features nowadays. The rest is happily provided at the library level by the community (which is still very prolific).

And it’s not tied to the jvm per say, look at clojurescript (and derivatives) or the upcoming jank.

It’s far from dead. As much as I like CL, the ecosystem is a bit of a desert compared to the jvm.

Wow. I clicked on your user name for some reason. You've been here 19 years and only have 34 karma and made only 16 comments!

Anyway, I came here to say Clojure also targets JavaScript and could target more like ClojureCLR https://clojure.org/about/clojureclr

Here, have another karma point!

Thanks! Long time lurker indeed.

I also forgot the very solid ClojureDart.

The JVM has suffered a fate worse than death: it's become so wildly successful that it's boring. So much enterprise shit runs on Java that it has sort of faded into the background noise of civilization and, like the System/360 (now Z/OS) before it, doesn't grab headlines anymore.

Which makes Clojure extra tempting because there is a bit of a infectious way to get Clojure i to corporations when you are always just handing the ops guys a "Java" we app bundled as a jar but secretly inside it's all Clojure compiled classfiles that work perfectly run on many JVM-based web servers with no additional effort.

I think Rich even alludes to this fact in one of his talks where it would be disallowed to run Ruby/Python/Rust whatever but it's Java then it's a know entity.

Yeeeeah, except we're living in the DevOps era, which means things like "thinking about how this will be built and deployed" is now the devs', therefore the whole organization's, responsibility, and so you have to think about whether your CI/CD pipeline can accommodate, or be made to accommodate, the Clojure compiler, leiningen, et weary cetera.

There's another, orthogonal, aspect: I half-jokingly suggested Clojure as a substitute for one of the DSLs we use at work, and my idea was shot down by a teammate based on the reasoning that Clojure is hard and most of the Java devs (not my team, of course) in the shop are not up to learning it or coding in it. So that's another thing to consider: when you leave the company, who else will be up to maintaining what you produce?

Both of these considerations weigh strongly against attempts to "sneak Clojure in through the back door".

Although niche, things are pretty lively in the community. Among other things this year great progress was made on Jank, the native LLVM-based implementation with seamless low-level C++ interop. As part of that work a test suite is being created [0] and now includes runners for all of the major implementations to compare compatibility, next best thing besides a formal specification.

[0] https://github.com/jank-lang/clojure-test-suite

I frankly miss the JVM. I work almost exclusively in Rust these days and haven't worked in Java or Scala since 15 years ago, and I do prefer working closer to the metal.... But... The JVM is an amazing mature runtime with a boatload of tooling. JMX, which has been there since almost the beginning, is the kind of thing missing from almost everything other managed runtime I've worked with.

The amount of R&D that has gone into making it execute with good performance, and its overall stability...

Yeah, it's got the curse of being boring.

I do think it is perhaps unfortunate that Clojure is tied so heavily to the JVM, because I actually don't think it gains much from that ecosystem... but it's a product of the time it was first written.

Actually hell. I'm between jobs, I like Lisp, and I miss the JVM. I've never worked in Clojure, but does anybody want to hire me to work in it? :-)

> I do think it is perhaps unfortunate that Clojure is tied so heavily to the JVM, because I actually don't think it gains much from that ecosystem... but it's a product of the time it was first written.

When I was doing more Clojure, I loved that it was on the JVM because it meant I got to use every Java library under the sun. There are tons of battle tested Java libraries that didn't have to be rewritten in Clojure, and getting to use them for approximately zero financial and runtime cost was a HUGE benefit of Clojure compared to other niche FP languages.

I don't care if it's niche if it solves my problems and gets the job done faster.

JVM is very much not dead even slightly. They just released virtual threads, which are ridiculously awesome. Also it's not tied to a single platform, clojurescript lets you write clojure in browsers and on node.js, and babashka lets you use clojure in a scripting environment via a single executable

I haven't tried clojurescript but I'm fearful of languages that run on top of other languages or platformks, because of complications that produces for debugging.

How do you debug ClojureScript? Can you modify the source-code while in the debugger? That is a huge time-saver, you debug and see a typo and fix it right away. My preference are influenced by my background in Smalltalk's "live" environemnt: you see the variables, the stack, and can change anything without having to stop the debugging session and then have to go back to the "editor" and then locate the place you (now know) you want to modify, and then start again.

Hm I definitely haven’t tried a debugger! I’m not sure if that’s a PITA to set up. I had a terrible time trying to get a debugger working with typescript on top of node.

Since clojure is so REPL heavy I haven’t felt like I’m missing a debugger too much. But the smalltalk live environment sounds ridiculously cool. I do end up using REPLs to remote programs (even prod lol) pretty often, which is pretty crazy for me coming from a node background

You're saying that Clojure is looking more dead, so you suggest... Common Lisp? That looks considerably more dead than Clojure.

I'm not sure that Common Lisp looks less dead, but rather, more eternal.

Clojure is not going anywhere anytime soon.

It sees plenty use as Clojure/Clojurescript and Babashka. (and other niche variants). Jank is shaping up to be real nice too.

How does Clojure do on McCarthy's desiderata from this paper, as you see it?

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