> async/await is also available in a bunch of other languages, including F#, C#8, Haskell[...]
Haskell (GHC) does not provide async/await but uses a green thread model.
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Haskell (GHC) does not provide async/await but uses a green thread model.
As I understand it async-await is syntax sugar to write a state machine for cooperative multitasking. Green "threads" are threads implemented in user code that might or might not use OS threads. E.g.:
- You can use Rust tokio::task (green threads) with a manually coded Future with no async-await sugar, which might or might not be parallelized depending on the Tokio runtime it's running on.
- ...or with a Future returned by an async block, which allows async-await syntax.
- You can have a Future created by an async function call and poll it manually from an OS thread.
- Node has async-await syntax to express concurrency but it has no parallelism at all since it is single-threaded. I think no green threads either (neither parallel or not) since Promises are stackless?
Is this a new usage of the term I don't know about? What does it mean? Or did I misinterpret the "but"?
As a non-Haskeller I guess it doesn't need explicit async-await syntax because there might be some way to express the same concept with monads?
[1] https://www.cambridge.org/core/services/aop-cambridge-core/c...
Well, I haven't used Haskell in a few years, so I could absolutely be wrong. That being said, I'm almost sure that I saw a presentation by Simon Marlowe 15-20 years ago demonstrating GHC with a multicore scheduler (alongside `seq` and `par`). Also, from the very same Simon Marlowe, there's a package called `async` https://hackage.haskell.org/package/async which basically provides async (no await, though).