Georges Boris (May 28 2022 at 14:55): Georges Boris (May 28 2022 at 14:55):Hey folks!
Would it be possible, in theory, for Roc to be compiled to JS through a platform?
I can imagine that platforms can only access their API's, right? So the compiled Roc itself would still be in another format (binary?) so a platform by itself would never be able to do it?
I'm 100% sure this has been asked before but I couldn't find it... thanks! :grinning_face_with_smiling_eyes:
Brian Carroll (May 28 2022 at 17:51):Interesting question! Are you aware that we already compile to WebAssembly? That's a much more practical target for Roc, since a lot of the compiler is focused on things that make sense for binary output formats that operate on bytes in memory.
In JS it's a bit unnatural to express things like that... Although I suppose it must be possible using a Uint8Array. But you'd end up recreating a slower implementation of WebAssembly!
Brian Carroll (May 28 2022 at 17:54):In the examples folder in the repo, one of the examples displays the words "hello world" on a web page using WebAssembly.
Georges Boris (May 28 2022 at 18:10):hey @Brian Carroll ! thanks for the reply!
I'm aware of WASM support but I was wondering how practical would be for other runtime representations - even if slower! currently WASM is slower in theory but since DOM manipulation still needs JS you end up slowing things down if you need a lot of interop, right? and you end up with larger bundles.
I'm aware it has been stated before that Roc doesn't aim at replacing web languages like Elm but I wonder if that is a non-goal or if it's not even a possibility if someone tried to do it. Makes sense?
Brian Carroll (May 28 2022 at 18:23):Yes that's right, you need JS/Wasm interop stuff to manipulate the DOM. I built a C backend for the Elm compiler to target Wasm and that was the main issue with it.
From that experience I concluded that if you try to convert complex Wasm structures to complex JS structures, it will be slow.
I think it can be fast if you design the whole system around that Wasm/JS boundary and minimise the JS. All you really need in JS is a small number of DOM API functions and a TextDecoder.
You don't want an overly general system that can convert any Wasm structure to any JS structure, like wasm-bindgen tries to do. That's always going to be slow. You want something that a virtual DOM and nothing else, and is excellent at that one thing.
Brian Carroll (May 28 2022 at 18:25):So to your actual question on whether it's possible... Well in theory you can translate any set of bytes to any other set of bytes. You could build a new Roc compiler!
Georges Boris (May 28 2022 at 18:25):uhnn interesting! and with that in mind you can definitely make it a platform, right?
sorry for the ignorance but is the wasm bundling size these days still a "problem"? or is it something that has been getting better over time?
Brian Carroll (May 28 2022 at 18:25):Could you fit it into the current one without major surgery everywhere in a reasonable amount of time and effort? I'm not sure, I'd have to think about it a bit more!
Brian Carroll (May 28 2022 at 18:26):I don't understand the connection with platforms, can you elaborate?
Brian Carroll (May 28 2022 at 18:26):What would the platform do?
Brian Carroll (May 28 2022 at 18:27):The compiler is the thing that translates Roc code to some other code format like x86 instructions or Wasm instructions or JS. The platform doesn't do that
Brian Carroll (May 28 2022 at 18:29):If you're used to Elm then think of the platform as "the Elm runtime".
Brian Carroll (May 28 2022 at 18:30):In fact the elm runtime has a Platform module that is very similar to what we call a platform in Roc.
Georges Boris (May 28 2022 at 18:30):I'm just wondering about eventually using Roc fullstack for building the same things I currently use Elm for. I guess the platform could take a view abstraction and do whatever with it - but the runtime itself would continue to be WASM, right? (using the current wasm compiler)
Georges Boris (May 28 2022 at 18:31):for the bundle size to be more optimized (not use wasm) I would need to properly work on a compiler and not a platform afaik
Brian Carroll (May 28 2022 at 18:32):What gave you the idea that Wasm bundles are always larger than JS bundles?
Brian Carroll (May 28 2022 at 18:33):I don't see any reason for that, maybe I'm missing something
Georges Boris (May 28 2022 at 18:33):yeah! this is my assumed ignorance - this is 100% based on criticisms I have been hearing over time but not based on actual experience. (elm bundle sizes begin at sub-20kb as an example)
Brian Carroll (May 28 2022 at 18:37):It would be hard to get solid evidence for that, you'd need to compare the same app in each target somehow.
Brian Carroll (May 28 2022 at 18:38):I might be able to find some numbers actually, but they're on a machine I can't access this week.
Brian Carroll (May 28 2022 at 18:39):You might be hearing about very inefficient Wasm implementations with lots of big dependencies that aren't really necessary. Because rust and c libraries normally run on desktop where bundle size is irrelevant.
Georges Boris (May 28 2022 at 18:39):got it! but this is interesting - indeed there is nothing preventing wasm from anything. I had more blockers in mind for some reason.
Georges Boris (May 28 2022 at 18:40):things completely unrelated like GHCJS might have been mixed in my mind for some reason.
Brian Carroll (May 28 2022 at 18:40):If we do a web platform for Roc it would be completely dedicated and optimized for this, with no dependencies
Brian Carroll (May 28 2022 at 18:41):Or very few
Brian Carroll (May 28 2022 at 18:42):I have fairly clear ideas on how I would do it
Georges Boris (May 28 2022 at 18:42):and the roc runtime/compiled code wouldn't be large by itself by default, right?
Brian Carroll (May 28 2022 at 18:42):No I don't think so
Georges Boris (May 28 2022 at 18:53):@Brian Carroll awesome! got me excited to experiment :) thank you
Brian Carroll (May 28 2022 at 19:18):Great! I'm interested in this, so keep me informed and I'll be happy to chat about ideas if you like.
Last updated: Jul 26 2025 at 12:14 UTC