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Generators are dead, long live coroutines, generators are back | Inside Rust Blog

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Generators are dead, long live coroutines, generators are back | Inside Rust Blog

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  • The section titled “what is the difference” doesn’t explain what the difference is, only what a generator is (which I already knew).

  • The only language to get it right was Simula 67.

  • Simulation 67 keeps the coroutine data on the heap (it is garbage collected).

  • Guys and girls, This problem has been solved in 1980 already. Why are we still struggling?

    It's called Communicational Sequential Routines. Like, why do we have to come to full circles and Rust after a decade still hasn't solved the "Async"/Multithreading problem. It's mind boggling to me, Im sorry, people are gonna hate me for me being frustrated, but I just can't say that it's irritating that Rust, a language that really has offered many great ideas, STILL hasn't figured out how to properly do things like channels and sequential communication? A concept that has been invented since the 80's? Or if that doesn't fit at least see how it could fit Rust's standards?

    It's HORRIBLE that Rust as a language and community STILL uses Tokio and Async-Std and we can't even decide always which one of the two to use and while they also have some incompatibilities afaik, and this is just for ASYNC. Multithreading and Async? God bless your soul if you're going to do that in Rust, because prepare for debugging for days and for many weird issues and caveats.

    Go, a much MORE inferior in features language has done it. What makes it so difficult to inherent such or a similar approach? It's a simple concept. Channels. In and out. And syntax and scheduler like Goroutines to make it easy to have async AND multithreading without the caveats Rust has nowadays if you were going to do such thing.

    http://www.usingcsp.com/cspbook.pdf

    • First, this post has enough misconceptions about the state of async Rust that I don't think you've used it much, or at least not recently. Second, it demonstrates a huge misunderstanding of how Rust works vs Go that I don't think you appreciate why the feature set is different.

      To answer the first, tokio is compatible with Rust's standard async support, and there are alternative runtimes to tokio as well that are also compatible with std. I'm currently working on an async-heavy project, and tokio is an implementation detail and only imported when initializing the runtime loop, most of it is just standard async/await syntax. So the user doesn't need to care most of the time what async engine is running.

      Tokio and other runners can be configured to be single or multithreaded, the API is designed such that it doesn't matter which you pick. I run it multi-threaded, and I use channels as well to communicate across async contexts. My code is structured very similarly to how I'd structure it in Go, it just doesn't have the same, clean syntax.

      What makes it so difficult

      A few things:

      • Go has a massive runtime which handles everything from memory management to scheduling
      • Go has very limited memory safety guarantees, and nothing to prevent you from shooting yourself in the foot with concurrent memory access
      • Go was designed around goroutines and channels as first class features, Rust adds it as an option (compare regex in perl vs other languages, lists in lisp vs other languages, etc)

      The first two are the most important here.

      Rust has no runtime, so it can't and won't do things like provide a default async runtime or scheduler implementation. This means you'll always need to configure and start your async engine, which means it needs to be modular. It turns out Rust doesn't need a default implementation to help libraries abstract over async, it just needs a handful of traits. This also means standard libraries won't plug in to the scheduler (e.g. when a socket or file read blocks in Go, it yields to the scheduler, whereas in Rust it just blocks), so you'll need an async-aware alternative if you want to avoid blocking. With Rust, you don't pay a penalty if you don't want async, but you do in Go because it's baked in to the scheduler, standard library, and language syntax.

      One final quip about Go since I have used and loved it since day 1 (convinced boss to switch once 1.0 landed and we didn't look back). For all of the features Go provides over async, there are still a lot of surprises. For example, why is map not threadsafe? The standard library bakes in async, why not make map atomic? Slices have a mostly safe interface, but they also do surprising things (e.g. you can copy over its backing array outside the bounds of the slice), and they could easily be made atomic and thus (mostly) async-safe. So Go gives you a lot of built-in features, but doesn't go far enough to make it actually safe.

      And that brings me to my second point: memory safety. Rust won't let you do stupid things like write to a Vec or HashMap from multiple parallel execution contexts, whereas Go will. So while you give up certain syntax niceties, you preserve memory safety, so your code in Rust will always be memory safe even if you get lost in the syntax (which isn't that bad imo). And since everything is modular, you can replace parts as needed if you need to hit certain performance targets or something.

      You can still use channels and spawn coroutines, the syntax just isn't built in. And that's my third point, Rust isn't designed around any given use case, whereas Go is. So if syntax matters more than the benefits Rust provides, use Go. But if correctness is more important and you're willing to put up with some verbosity, use Rust.

      • Bro, it's not a battle. Like Golang Vs Rust. You treat it like a battle. "Go has very limited safety guarantees in comparison to Rust", "Go was designd around go routines, Rust adds it as an option" as if this is an advantage? How exactly?

        In any case, just look at Primeagen, any Rust programmer. Or do your own websocket server in Rust vs Go.

        Go = 10 minutes Rust = 10-20 hours.

        Does that mean that Rust is worse? NO. Absolutely No.

        You though make it seem like a hecking war like Go Vs Rust. Jesus chill bois. I know Rustacians are fanatics but chill.

        Go provides you a type-safe way and a clean-very-self-documentable, efficient, multithreaded/async/parallel way (yes yes ... I know ... yes ... they're all different, don't be nitpicky jesus christ, I know somebody in the commends will try to "correct me"), to write programs VERY fast in a as type safe way as a company usually needs.

        I'm not paid by the hour, I'm paid by the month. I'm not gonna spend 3 months just dealing with Tokio, Features, "async" which is not a feature but an option in Rust which is horrible nowadays, our machines are VERY powerful to be able to do async things very fast, it should have been a feature which you might use it or not like in Go. NOBODY forces you in Go to write a Goroutine, it's just a language feature, get it? Mutlthreading, a hell in comparison with go.

        Like, sometimes we just have to accept ... each tool is best for its own job.

        You want a VERY performant CLI tool? A system kernel mod or something that has to do with memory so much that Go will just be really bad decision? Go to Rust or C++. EACH TOOL, FOR ITS OWN JOB. It is not a heckin battle.

        And sometimes we just have to accept, that no language is flawless. Stop trying to excuse the fact that Rust is very slow to program on and document in comparison with languages like Go. Go is not flawless either, what language is?

        Go

        • has no pattern matching
        • has garbage collection. horrible if you want an app which is very memory heavy and with many arrays, structs and lists.
        • Structs - Structs fucking amazing in Rust. I love them to the point I almost said to myself "Im not going back to Golang".
        • Enums ... same with structs. They're very powerful
        • Generics - Whoever "Go" elitist says "But but ... Go has generics" ... I swear to god, I will pick his nails and throw his body to the ocean. Generics in Go suck. Still. Even 1-2 years after their release (1.18 was it? and we're at 1.21 at go?) Rust has proper generics

        Like do you get me? You make it seem like a battle between languages. Stop being fucking elitists. No language is perfect. Rust is SLOW to PROGRAM on. FAST on performance, but just to deal with the borrow checker its like it's programming for you instead of you programming for the compiler and some changes require massive changes. And this steap learning curve, and mistakes, and really big complexity, make Rust just a NONO for small project. Do you really wanna make a websocket server in Rust? Be my guest. In Golang I can make it in ~50-100 lines and it's perfect. But in Golang, when memory performance starts to matter and it's not insignificant, which happens after decades most likely when you already have the budget to refactor, like Discord did (which just burns money of its investors btw it has no profit).

        My point being 1 -> STOP being fucking elitists and "RUST IS THE BEST FUCKING LANGUAGE". No its fucking not. No language is. Or trying to excuse the choice of not having Async by default and being so overly complex at times you just require hours to debug some sht.

        1. -> EVERY language has its advantages and its disadvantages. CAN you please ... for god's sake ... accept that? Just for once? Rust has big flaws when it comes to async, parallel and multithreading programming. It's a mess. You'll be debugging for hours or days.

        2. -> Every language = a tool. Every tool has is used for a specific reason. It seems that Rustaceans fell in love with Rust so much they wanna make Rust everything. Dude or girl, girl or dude, that's just ... bogus and out of mind. It means you're the cult. You're not in a cult, you're the cult when you do that. No language is perfect for anything.

        3. Accept judgement. Okay? Languages just suck at somethings. Every - single - one - of them. NodeJS at multithreading, typesafety, documentation, memory (copying everything) and making programmers careless. Go at not having enums, proper generics, pattern matching, garbage collector etc. Rust at multithreading + async + parallel + making simple servers + borrow checker making it a PITA to program and design things the way you want to, instead you design things the way the borrow checker wants and it drains MUCH of your time redesigning things when you make mistakes, youre a human, u will make mistakes. ... C++ and being so overly complicated you can barely read it and it makes stupid people think they're smart because they used the "new C++22 feature" while there was a much simpler and efficient way to do it. But hey, they're smart because "they follow the news and C++ has a new feature they wanna use in production which makes code slower". C for being so simple and barebones and without language tools, like C++ too, it requires things like Ninja etc. to compile the headers etc. or do anything complicated. Thus why it's not used by companies to make simple microservices. hello? It's a PITA to write in languages like C++/C/Rust for a simple micro-service, and insignificant until you are actually a multi-million-hundrends or billion company with much traffic. Like, accept fucking judgement. It's not bad for once. Some languages just such at some things. Even my brother, who works at Cadence, a software company for firmware for Chips and testing chips like ARM for Apple etc. a fortune 500 company, used python because it's just ... more convenient instead of having to recompile C++ every f'in time on each client's CPU and there are countless when you're such company. But Python is really bad at many things as well, but see? It has its own very nice uses despite that my brother works for almost a decade with C++, he chose python for that job because he knew it was the correct choice. Stop trying to excuse everything.

        Rust sucks at async & multithreading. Period. In comparison with other languages, it's a PITA to debug and deal with. That's why the main rule in multithreading is "do not use multithreading unless you have to". Well, in Go, you kinda dont have to think about that despite that you have to learn some patterns for data-races safety. I can make you a multithreaded program barely thinking about the multithreaded-side of things because that's the scheduler's job. It was built for it. But it sucks at many other things. Like Rust, just accept that and we can keep going on with our lives

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