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Coroutines really are powerful. Here's to hoping Rust stabilizes generators (full semicoroutines, not the enhanced iteration construct) sooner rather than later

Coroutines really are powerful. Here's to hoping Rust stabilizes generators (full semicoroutines, not the enhanced iteration construct) sooner rather than later. It would give programmers greater control to express state machine logic without being boxed into async/await. I do wonder if the `Context` parameter used for async tasks is appropriate for arbitrary generators, so if someone could chime in on this I would be grateful.

mratsim 3y ago
Or provide continuations and use them to implement coroutines.
- qudat 3y ago
  A couple of us have been experimenting with deliminited continuations and I think it’s gonna take off soon in TS https://youtu.be/uRbqLGj_6mI?si=kgKKjpCnehJ9bpIG https://youtu.be/uRbqLGj_6mI?si=kgKKjpCnehJ9bpIG https://github.com/neurosnap/starfx https://github.com/neurosnap/starfx https://github.com/thefrontside/effection/tree/v3 https://github.com/thefrontside/effection/tree/v3
  - vacuity 3y ago
    To my understanding, delimited continuations and coroutines are equivalent in power. Out of curiosity, can delimited continuations be implemented as efficiently (in Rust or otherwise) as stackless coroutines?
  - vore 3y ago
    These don’t look like continuations to me, just ways to use generators? Continuations would involve reifying the current control flow into a value, which these examples don’t seem to do and still rely on generators to yield control.
    - qudat 3y ago
      These libraries rely on deliminited continuations: https://github.com/thefrontside/continuation https://github.com/thefrontside/continuation Because of this tiny implementation we are able to express any async flow construct with less code than relying on something like async/await or callbacks.
- smasher164 3y ago
  Single-shot continuations in the form of lexical effect handlers would be a good fit for a systems language nowadays. I feel it's a bit too late to staple that onto Rust though.
pflanze 3y ago
I've been using genawaiter[1] for writing generators in Rust. Are there things you can't build on top of async-await? Or is it just that it's simpler without that indirection? [1]: https://crates.io/crates/genawaiter https://crates.io/crates/genawaiter
- vacuity 3y ago
  I was thinking that the semantics around async/await (function coloring) would make some usages more frustrating. This crate probably sidesteps that, if it is a problem at all. I have a bad habit of not dabbling around when I lack understanding.
- duped 3y ago
  This feels circular, since async/await is futures which are generators
SkiFire13 3y ago
I don't think `Context` is appropriate for generic generators, since it has no way to get data in or out of the `async` block. The more general `generator` feature allows a custom context type though.
- vacuity 3y ago
  I must've looked at an outdated design or something. Thanks for the info.

mratsim 3y ago

Or provide continuations and use them to implement coroutines.

qudat 3y ago
A couple of us have been experimenting with deliminited continuations and I think it’s gonna take off soon in TS https://youtu.be/uRbqLGj_6mI?si=kgKKjpCnehJ9bpIG https://youtu.be/uRbqLGj_6mI?si=kgKKjpCnehJ9bpIG https://github.com/neurosnap/starfx https://github.com/neurosnap/starfx https://github.com/thefrontside/effection/tree/v3 https://github.com/thefrontside/effection/tree/v3
- vacuity 3y ago
  To my understanding, delimited continuations and coroutines are equivalent in power. Out of curiosity, can delimited continuations be implemented as efficiently (in Rust or otherwise) as stackless coroutines?
- vore 3y ago
  These don’t look like continuations to me, just ways to use generators? Continuations would involve reifying the current control flow into a value, which these examples don’t seem to do and still rely on generators to yield control.
  - qudat 3y ago
    These libraries rely on deliminited continuations: https://github.com/thefrontside/continuation https://github.com/thefrontside/continuation Because of this tiny implementation we are able to express any async flow construct with less code than relying on something like async/await or callbacks.
smasher164 3y ago
Single-shot continuations in the form of lexical effect handlers would be a good fit for a systems language nowadays. I feel it's a bit too late to staple that onto Rust though.

pflanze 3y ago

I've been using genawaiter[1] for writing generators in Rust. Are there things you can't build on top of async-await? Or is it just that it's simpler without that indirection? [1]: https://crates.io/crates/genawaiter https://crates.io/crates/genawaiter

vacuity 3y ago
I was thinking that the semantics around async/await (function coloring) would make some usages more frustrating. This crate probably sidesteps that, if it is a problem at all. I have a bad habit of not dabbling around when I lack understanding.
duped 3y ago
This feels circular, since async/await is futures which are generators

SkiFire13 3y ago

I don't think `Context` is appropriate for generic generators, since it has no way to get data in or out of the `async` block. The more general `generator` feature allows a custom context type though.

vacuity 3y ago
I must've looked at an outdated design or something. Thanks for the info.