I submitted this because I've been getting really interested in effect systems, especially now that OCaml 5 has a working production quality example they'd been iterating on for years prior. I wanted to see what it'd look like in Rust too so maybe one day we can get rid of async function coloring, and with OxCaml by Jane Street maybe we could see how that would look in practice.

Another reason for submitting this is that React actually has a quite robust effect system, that people don't necessarily realize they're using one every day if they use hooks.

I've been using it for 5+ years and my 4 men team can scale to supporting 6 different products (each running millions $ in business, sometimes daily), as we reuse the same patterns and architecture. This would not be possible without Effect, even though I'm lucky to have terrific engineers as colleagues, we just wouldn't be able to without the endless goodies from Effect.

The amount of features is basically endless, as effects and runtimes weren't enough, from SQL to AI, from effectful schemas (encoders/decoders), first-class OTEL support, CLI, debuggers, editor extensions, and many others. There's still countless modules I have yet to see or use.

Runtimes are available for each platform, including cloudflare workers.

There's absolutely nothing in TypeScript land to have such a wide scope.

v4 will also bring durable workflows (I'm already using v4 beta and that feature in prod) and many other goodies. That's quite important for us needing to have procedures that need to survive redeploys, crashes, etc.

I would never go back to writing standard TypeScript.

There is a learning curve, but you can adopt it incrementally. Nobody adopting it has ever gone back.

That being said, it would be great if there was a proper effect-based language (I've seen few projects like Effekt, but there's way too many things missing) as TypeScript is verbose, and effect adds its own verbosity.

[1] https://effect.website/

No ASM involved so technically portable (although it depends on built-in).

Flix equivalent (copy paste to https://play.flix.dev/):

    eff Pick {
        def pick(): Int32
    }

    def body(): (Int32, Int32, Int32) \ Pick = {
        let a = Pick.pick();
        let b = Pick.pick();
        let c = Pick.pick();
        (a, b, c)
    }

    def handlePick(f: Unit -> a \ ef): List[a] \ ef - Pick =
        run {
            f() :: Nil
        } with handler Pick {
            def pick(_, resume) =
                resume(1) ::: resume(2) ::: resume(3)
        }

    def main(): Unit \ IO =
        println(handlePick(body))