Rust @programming.dev van2z @lemmy.world 10 mo. ago

Coroutines / Generators - Resume with a value after a Yield?

Please let me know if this is possible...

I would like to be able to have a coroutine / generator yield to resume with a value.

This is a simplified version of what I am looking for:

https://play.rust-lang.org/?version=nightly&mode=debug&edition=2021&gist=8be2f397f600236b66970fce5c0ecab6

In this example, yield would end up requesting from the parent, that it wants to read the next byte, and the parent would resume the coroutine with the next byte. (In this case, it's hardcoded to 54, but it can be any value.)

Yet it seems like Rust doesn't have the ability to resume a yield with a value.

Is there any way I can get this to work?

7 comments

I think your playground link might be broken because of all the amp bits.
- You are right. I fixed it just now. That is an annoying "feature" of lemmy...
  
  Converting ampersands to say amp instead is a bug that got fixed in version 0.19, world hasnt upgraded yet though
  
  Amp is a Google thing, not a Lemmy thing. I can't see the original, so I can't tell if it's a Lemmy thing or some client that has issues.
Is there any way I can get this to work?

Probably not, but it has been suggested. I'm a little surprised that yield is an expression here, because the RFC seems to only allow it as a statement.

The only way I can think of doing it is to use something like a channel (send the receive end to the coroutine) and read right after yielding. Nothing in the API suggests that they've taken that into account yet.

Maybe it's going to be addressed in a follow-up RFC? Like maybe there will be an optional resume_with_value() or something?

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