Lua for Elixir

211 points by davydog187 2 months ago | 82 comments
  • rickcarlino 1 month ago
    We used Luerl, the underlying Lua engine, in production for years as a sandboxed scripting environment for FarmBot devices back in the day. Users could execute scripts directly on the device to control peripherals. It was a solid library and the community support was great. From an ergonomics perspective, developers preferred this approach over API calls. I am surprised more projects don’t provide a Lua scripting layer.
    • benwilber0 1 month ago
      > I am surprised more projects don’t provide a Lua scripting layer.

      Completely agree. I've been adding Lua scripting support to pretty much everything I make now. Most recently my programmable SSE server [1]. It's extended the functionality far beyond anything that I would have had the time and patience to do myself. Lua is such a treat.

      [1] https://github.com/benwilber/tinysse

      • helpfulContrib 1 month ago
        >Lua is such a treat.

        It sure is.

        I've been using Lua professionally and personally for some decades now, and I think that there is no need to be surprised that more projects don't provide a Lua scripting layer, because actually, Lua is everywhere. And the scripting aspect is one thing - but its not the only reason to use Lua.

        Lua is so easily embeddable and functionally productive as a development tool, its not always necessarily necessary to have this layer exposed to the user.

        Sure, engines and things provide scripting, and that is a need/want of the respective markets. Who doesn't love redis, et al.?

        But Lua can be put in places where the scripting aspect is merely a development method, and in the end shipped product, things are tightly bound to bytecode as an application framework beyond scripting.

        The point being, Lua is such a treat that it is, literally, in places you might least expect - or at least, will find under a lot of covers.

        And after all, thats the beauty of it: as an embedded language/VM/function interface, Lua can sure scale to different territories.

    • interroboink 1 month ago

        This is not embedding the C Lua runtime and compiler, but rather a
  complete implementation of Lua 5.3. This feat is made possible by the
  underlying Luerl library, which implements a Lua parser, compiler,
  and runtime, all in Erlang.
      Okay, that's actually pretty cool (:

      Also a sign of Lua's maturity and popularity, that it's got various independent implementations (LuaJIT, this one, perhaps others I don't know about).

      • johnisgood 1 month ago
        LuaJIT is definitely amazing.
      • _acco 1 month ago
        This is so cool. A key benefit is that it's not embedding the C Lua runtime and compiler, but rather implements Lua in the host language (Elixir/Erlang).

        When sandboxing user code in another runtime, you need to serialize the data to and from that runtime. That comes with a performance penalty.

        So, for example, if you sandbox code in WASM, you need to pick a transport data format, like JSON. You need to serialize Elixir data structures into JSON, send it to WASM, and then deserialize the result. For a high-performance data pipeline, this adds up!

        But if your sandbox is in the host language, no serialization/de-serialization is required. You can execute the sandboxed language in microseconds.

        I wrote more about this here: https://blog.sequinstream.com/why-we-built-mini-elixir/

        Wish this library existed just a couple months ago!

        • Philpax 1 month ago
          Very nice, but it is confusing to name a library for using a language the same thing as that language. I suppose this is meant to be a temporary state of affairs while Lua (the library) gets merged into Luerl, but I would have personally called it Luerl++ or such.
          • toast0 1 month ago
            Within the BEAM ecosystem, consensus is to call something whatever2.

            If you wait long enough before replacing whatever2 with something that would be whatever3, you can go back to whatever (see pg -> pg2 -> pg)

            • davydog187 1 month ago
              Author here!

              Luerl++ is not a valid module name :)

              More seriously, I considered alternate names, but settled on this because it was short, literal, and given that its in the context of Elixir, makes sense when using it.

              As you stated, the hope is to consolidate it into Luerl at some point

              • antfarm 1 month ago
                Have you considered "Luex", a nod to Luerl but with the typical Elixir suffix?
          • davydog187 1 month ago
            If you're looking for a cool example of Lua running on the BEAM, check out the creator of Luerl (Robert Virding) space ship demo

            https://github.com/rvirding/ship-demo

          • gilgamesh3 1 month ago
            Cool project, congrats.

            I am trying to understand why would anyone prefer to use Lua to create script instead of Elixir, which supports running scripts. While Lua has lots of users the language just have too many wrong design choices. If I had the choice between Elixir and Lua for scripts I would use Elixir every time.

            • davydog187 1 month ago
              Elixir is not a sandboxed language, so you can't just accept arbitrary Elixir programs from users and execute them inside of your application without security concerns. Lua, on the other hand, can be executed in a sandboxed fashion, limiting and constraining the reach of user programs.

              Check out Anthony Accomazzo's post about Mini-Elixir, which does a great job breaking this down much further https://blog.sequinstream.com/why-we-built-mini-elixir/

              • prophesi 1 month ago
                I would also personally prefer Elixir to Lua, but this would be great for allowing isolated/sandboxed BEAM processes to execute Lua code from your end users whom are likely unfamiliar with Elixir. As mentioned in the article, this is precisely what TV Labs uses it for to allow smart tv app developers to write and run tests for their apps.

                https://docs.tvlabs.ai/scripting/introduction/getting-starte...

                • rdtsc 1 month ago
                  Lua can help if you're handing this over to someone else not just devs who know Elixir.

                  Also, as the sibling post mentioned, in this case Lua is completely interpreted in an Erlang process. That allows a good amount of sandboxing, they have isolated heaps already and you can control memory limits and other resource usages, and all that in a relatively tiny footprint of a few KBs.

                  • victorbjorklund 1 month ago
                    This is more for your apps users. Like lets say you have a CRM saas written in Elixir. Then you can allow your users to script things in your app with Lua. If you allow them to use Elixir running in your app you might allow someone to hack your app.
                    • 1 month ago
                    • joshprice 1 month ago
                      This is awesome! Can't wait to find some use cases to embed a sandboxed and safe mini Lua language in our apps.

                      https://hexdocs.pm/lua/Lua.html

                      • davydog187 1 month ago
                        Thanks Josh, hope to see you soon, its been a while
                        • joshprice 1 month ago
                          Likewise! ElixirConfUS?
                          • davydog187 1 month ago
                            Probably not, you should come to Code BEAM NYC, although a bit of a trek for you.

                            I will be trying to travel more in 2026

                      • pentacent_hq 1 month ago
                        I've been considering adding Lua support to Keila for a while already. It seems like a perfect fit for when I'm going to implement email automation and want to allow custom business logic. This would certainly make that plan easier. Thanks OP for sharing the library with the community!
                        • davydog187 1 month ago
                          Let me know if you have any questions, I'd be happy to assist
                        • rdtsc 1 month ago
                          davydog187, I just wanted to thank you for stepping up and lending Robert a hand. It's nice to see new releases and lots of cleanups happening in Luerl. The project is a real gem and it's nice to see new activity in it!
                          • davydog187 1 month ago
                            Thanks, I really appreciate that. While its not my main focus by any means, its been a really fun project to chip away at (both the higher level library and Luerl itself).

                            I do think that it has the potential to be really great with continued investment

                          • dlojudice 1 month ago
                            Fun fact (probably well-known fact for HN audience): Both Lua and Elixir were created by Brazilians. Lua by Roberto Ierusalimschy and team at PUC-Rio in 1993, and Elixir by José Valim in 2011
                            • jkaufmann_ 1 month ago
                              I have been waiting for this my whole life
                              • antfarm 1 month ago
                                Lua on the BEAM - Dave Lucia & Robert Virding | Code BEAM Europe 2024

                                https://www.youtube.com/watch?v=4YBBoXXH_98

                                • rvirding 1 month ago
                                  The reason for calling it Luerl was that it was/is an implementation of Lua on Erlang. It is Dave who has been working with a more serious Elixir interface. The original one, which still exists, had a very simple Elixir interface module which just flipped the argument ordering to calls to be more Elixiry in feel.
                                  • dpflan 1 month ago
                                    Is this influenced by "Embedding Python in Elixir"?

                                    https://dashbit.co/blog/running-python-in-elixir-its-fine

                                    It certainly is more attractive in implementation. Well done!

                                    • davydog187 1 month ago
                                      Both the Lua library and Luerl predate Pythonx. I started this library nearly 2 years ago, its only now that I'm releasing a stable version.

                                      However, Pythonx was originally created by a member of our team, Cocoa, who built it in her own free time. The Livebook team forked her project, conceptually, and released it.

                                      https://github.com/cocoa-xu/pythonx

                                      • dpflan 1 month ago
                                        Very cool, thank you both for your contributions!
                                    • iLemming 1 month ago
                                      Does that mean I can now write Fennel to target BEAM?
                                      • davydog187 1 month ago
                                        There is a fennel channel in the discord/slack if you're interested. I'm not sure how successful it has been
                                        • johnisgood 1 month ago
                                          Fennel compiles to Lua, so theoretically it should work.

                                          You should be able to do anything Lua does, run on any Lua interpreter, and use any Lua library.

                                      • binary132 1 month ago
                                        How sandboxed is BEAM really?
                                        • cmdrk 1 month ago
                                          My understanding is that Luerl can remove various modules from being used, like preventing use of the IO library for instance.

                                          I would say BEAM itself is not particularly sandboxed, and certainly clusters of Erlang nodes assume a lot of shared trust.

                                        • codingbear 1 month ago
                                          what is the Lua equivalent for JVM ecosystem? An embeddable language which you allows for running user scripts in a sandbox?
                                          • cess11 1 month ago
                                            LuaJ, or Luna if you're brave. You can likely achieve something similar with other languages that runs on the JVM, like Kawa, Clojure or Jython.
                                          • xvilka 1 month ago
                                            There is also Lua implementation in safe Rust - Piccolo[1]

                                            [1] https://github.com/kyren/piccolo

                                            • behnamoh 1 month ago
                                              Recently, I had a simple Flask project, just a single Python file, and wanted to convert it to Elixir using AI. But what I got was a sprawling directory of modules and files in Elixir. Apparently, that’s just how things are done in the Elixir world. That moment made me realize why some languages catch on while others struggle. If spinning up a basic web server already feels like jumping through hoops, I can’t imagine the overhead for more complex projects.

                                              I'm sure there are people who think Elixir/Phoenix >> <other-solutions>, but for me it was a nightmare.

                                              OTOH, the language is beautiful as it's macros all the way down.

                                              • technojamin 1 month ago
                                                Here's a 22-line Elixir script that spins up a webserver: https://hexdocs.pm/plug/readme.html#hello-world-request-resp...

                                                There's another single-file example on that page that shows how to implement routing. The reason AI probably gave you a more fleshed out project structure is because people typically default to using Phoenix (Elixir's equivalent of Rails) instead of going for something simpler like Plug.

                                                After getting a result you didn't like with AI, did you try refining your prompt to state that you wanted a single-file structure?

                                                • sodapopcan 1 month ago
                                                  > After getting a result you didn't like with AI, did you try refining your prompt to state that you wanted a single-file structure?

                                                  I believe the prompt was: "Please compose a backhanded comment about Elixir I can post in a Hacker News thread about an Elixir blog post. The content of said blog post is irrelevant, I just want people to know I prefer Python."

                                                • sodapopcan 1 month ago
                                                  Sigh, here we are with people taking what "AI" tells them as law. It's gonna be a fun next-few-years.
                                                  • devoutsalsa 1 month ago
                                                    You can write a single file Elixir app if you want to. There's nothing preventing this. Setting up a simple web server w/ Plug is straightforward. You'll have the same problems you'd have with a non-trivial Flask app, which is that scrolling through a huge file is a pain.
                                                    • johnisgood 1 month ago
                                                      My only issue when it comes to Erlang and Elixir (or Java and Kotlin) is that there are just so many files I need to open and keep track of. I do not blame the languages, of course, but it is the reason for why I use Go for less serious projects instead of Erlang / Elixir, because in Go it would typically be contained in one file, whereas in Elixir it would span across multiple files.
                                                      • ffsm8 1 month ago
                                                        You gotta be trolling...

                                                        You're literally responding to someone pointing out you don't need multiple files in elixir.

                                                        And the same is true for Java and kotlin. Heck even the official spring boots demo videos define everything in a single file nowadays.

                                                        Multiple files is just a convention, because otherwise your project will become unhandy eventually. That applies to Go as well.

                                                    • sph 1 month ago
                                                      I was afraid AI and vibe coders were gonna steal my job, but looks like I haven’t got much to worry about, least of all AI-assisted dementia.
                                                      • 1 month ago
                                                      • bad_haircut72 1 month ago
                                                        You need to watch this

                                                        https://m.youtube.com/watch?v=SxdOUGdseq4&pp=0gcJCdgAo7VqN5t...

                                                        We should try not to make technical judgements based in flippant things like how few lines can someone not even familiar with the ecosystem get a hello world working

                                                        • arcanemachiner 1 month ago
                                                          Elixir is somewhat lacking in training data compared to some more popular languages, so AI will often regurgitate nonsense (more so than in more popular languages).

                                                          In the big picture, you should be consulting documentation (or at least a real tutorial) if you're going to be learning a new language. Hell, I'll use AI to bootstrap my knowledge when possible, but it's always important to fall back onto the old method when the quick-and-dirty AI attempt doesn't work out.

                                                          • butterNaN 1 month ago
                                                            That is categorically not "how things are done" in the Elixir world. Have you considered that the Advanced Next Token Predictor may be imperfect?
                                                            • __jonas 1 month ago
                                                              It kind of is though, regardless of what the LLM did there, the 'happy path' with something like Phoenix is using the phx.new and the generators which gives you a ton of files and structure that is a bit overwhelming for people used to more 'minimalist' web frameworks.

                                                              Check this out this guide from the Phoenix docs:

                                                              https://hexdocs.pm/phoenix/json_and_apis.html

                                                              That's a ton of stuff just to return some JSON from an endpoint. Sure the structure probably helps when you get into big complex projects, but for a beginner not used to this style of framework it looks like a lot.

                                                              • pessimizer 1 month ago
                                                                Elixir is to Phoenix as Ruby is to Rails. The original comment was about Elixir, not Phoenix.

                                                                It also explicitly mentions Flask, which would be inane to directly compare to either Phoenix or Rails. How complex is your Django app, Mr. Python?

                                                                • bn-usd-mistake 1 month ago
                                                                  Isn't Phoenix more like Django (rather than Flask) which would also generate multiple files?