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Kotlin has solved colouring before loom -> https://medium.com/@elizarov/how-do-you-color-your-functions-a6bb423d936d https://medium.com/@elizarov/how-do-you-col

Kotlin has solved colouring before loom -> https://medium.com/@elizarov/how-do-you-color-your-functions-a6bb423d936d https://medium.com/@elizarov/how-do-you-color-your-functions... Go was the first to solve colouring but they have it seems a less type safe solution

pron 6y ago
Kotlin, like C#, has a two-colour, double API system for synchronous code on threads and on coroutines.
- The_rationalist 6y ago
  I don't understand, you can call a coroutine from a synchronous function and call a normal or suspend function from a suspending one. By colorless we mean that you can use a suspend return type directly and not through the ugliness of a promise. Kotlin did choose to have the suspend keyword but it's just an explicit type, kotlin could have had no suspend keyword and be officially colorless, it is technically colorless and is I believe the best of both worlds
  - pron 6y ago
    > I don't understand, you can call a coroutine from a synchronous function and call a normal or suspend function from a suspending one. Not without a syntactic distinction, and not without losing the performance characteristics you want coroutines to begin with. > By colorless we mean that you can use a suspend return type directly and not through the ugliness of a promise. That's not colourless. Colourless means that there is no syntactic distinction between sleep and delay. Two subroutines that mean the same but have a different syntactic colour. > kotlin could have had no suspend keyword and be officially colorless, It could not. You'd need to control the JDK to do that, or depend on class reloading, or pay a very high price in performance. Not to mention that it still wouldn't help when calling Java code (directly or indirectly) nor would it change how, say, JFR observes your program. The problem is that Kotlin has very little influence over the platforms it targets -- Java, Android, JS and LLVM (well, maybe it has some influence over Android) -- and so must do its best to implement its functionality on top. > I believe the best of both worlds We don't want two worlds. We don't need two worlds. We want one that behaves as it should.
MrBuddyCasino 6y ago
Golang occupies an interesting spot here. They never had to migrate from a predominantly blocking, thread-based ecosystem to async. Does Golang really have two colors, is explicit threading a thing (I honestly don't know)? Or is it really just one color, namely the async one?
- Skinney 6y ago
  Golang only has one colour. `funcA` works the same way in sync (`funcA()`) or async (`go funcA()`) context.
  - aliceryhl 6y ago
    Golang doesn't really have a sync context. It has one color because everything is async. The `go` operation is not comparable to `await`, rather it is comparable to spawning.
    - Skinney 6y ago
      There’s a difference between sync and async code in Go, which is why you have all the normal threading primitives like mutexes, semaphores and blocking queues/channels. The point is that functions themselves don’t come in sync or async flavors. Just like in Java.
      - aliceryhl 6y ago
        I don't think the existence of mutexes, semaphores and queues/channels imply that there is a sync version of Go. You can totally use those primitives in asynchronous Rust too. You call the queues blocking, but they aren't really in the sense of "blocking" usually used when talking about async in Rust. The Go runtime can and will preempt your Go code in the middle of waiting for a channel to run some other task, and this preemption is what makes it different from a blocking Rust channel. An async Rust channel will also make the calling function wait for messages when you await the receive method. Basically my point is that because any Go code can be preempted at any point, that makes all Go code async. The language not making you type await on everything doesn't make it sync.
int_19h 6y ago
Green threads have been around for a very long time before Go, and there's nothing specific about Go that made them solve any problem they didn't solve before. It just so happens that this is a solution that comes with many downsides, which is why it's not universally adopted. Indeed, Java itself had green threads (only!) in the first couple of versions.
- pron 6y ago
  Its downsides depend on the language. It works better in languages with GC than languages without, and it works better in languages that rarely rely on FFI than in languages that rely on it a lot. One of its major "downsides" is that it's just harder to implement than async/await, and requires control over the backend, something few languages have (even Rust is on top of LLVM). For example, Koltin just couldn't implement useful usermode threads because it has no control over the JDK.

pron 6y ago

Kotlin, like C#, has a two-colour, double API system for synchronous code on threads and on coroutines.

The_rationalist 6y ago
I don't understand, you can call a coroutine from a synchronous function and call a normal or suspend function from a suspending one. By colorless we mean that you can use a suspend return type directly and not through the ugliness of a promise. Kotlin did choose to have the suspend keyword but it's just an explicit type, kotlin could have had no suspend keyword and be officially colorless, it is technically colorless and is I believe the best of both worlds
- pron 6y ago
  > I don't understand, you can call a coroutine from a synchronous function and call a normal or suspend function from a suspending one. Not without a syntactic distinction, and not without losing the performance characteristics you want coroutines to begin with. > By colorless we mean that you can use a suspend return type directly and not through the ugliness of a promise. That's not colourless. Colourless means that there is no syntactic distinction between sleep and delay. Two subroutines that mean the same but have a different syntactic colour. > kotlin could have had no suspend keyword and be officially colorless, It could not. You'd need to control the JDK to do that, or depend on class reloading, or pay a very high price in performance. Not to mention that it still wouldn't help when calling Java code (directly or indirectly) nor would it change how, say, JFR observes your program. The problem is that Kotlin has very little influence over the platforms it targets -- Java, Android, JS and LLVM (well, maybe it has some influence over Android) -- and so must do its best to implement its functionality on top. > I believe the best of both worlds We don't want two worlds. We don't need two worlds. We want one that behaves as it should.

MrBuddyCasino 6y ago

Golang occupies an interesting spot here. They never had to migrate from a predominantly blocking, thread-based ecosystem to async. Does Golang really have two colors, is explicit threading a thing (I honestly don't know)? Or is it really just one color, namely the async one?

Skinney 6y ago
Golang only has one colour. `funcA` works the same way in sync (`funcA()`) or async (`go funcA()`) context.
- aliceryhl 6y ago
  Golang doesn't really have a sync context. It has one color because everything is async. The `go` operation is not comparable to `await`, rather it is comparable to spawning.
  - Skinney 6y ago
    There’s a difference between sync and async code in Go, which is why you have all the normal threading primitives like mutexes, semaphores and blocking queues/channels. The point is that functions themselves don’t come in sync or async flavors. Just like in Java.
    - aliceryhl 6y ago
      I don't think the existence of mutexes, semaphores and queues/channels imply that there is a sync version of Go. You can totally use those primitives in asynchronous Rust too. You call the queues blocking, but they aren't really in the sense of "blocking" usually used when talking about async in Rust. The Go runtime can and will preempt your Go code in the middle of waiting for a channel to run some other task, and this preemption is what makes it different from a blocking Rust channel. An async Rust channel will also make the calling function wait for messages when you await the receive method. Basically my point is that because any Go code can be preempted at any point, that makes all Go code async. The language not making you type await on everything doesn't make it sync.

int_19h 6y ago

Green threads have been around for a very long time before Go, and there's nothing specific about Go that made them solve any problem they didn't solve before. It just so happens that this is a solution that comes with many downsides, which is why it's not universally adopted. Indeed, Java itself had green threads (only!) in the first couple of versions.

pron 6y ago
Its downsides depend on the language. It works better in languages with GC than languages without, and it works better in languages that rarely rely on FFI than in languages that rely on it a lot. One of its major "downsides" is that it's just harder to implement than async/await, and requires control over the backend, something few languages have (even Rust is on top of LLVM). For example, Koltin just couldn't implement useful usermode threads because it has no control over the JDK.