Hi - I’m experimenting with

sequence {}

but getting “Restricted suspending functions can only invoke member or extension suspending functions on their restricted coroutine scope”. I can’t seem to find any information about this. Any pointers please? https://pl.kotl.in/B1hRgy_2m Presumably I need to use a suspending extension function of CoroutineScope?

See

@RestrictsSuspension

annotation docs https://kotlinlang.org/api/latest/jvm/stdlib/kotlin.coroutines/-restricts-suspension/index.html

Ok thanks. I was thinking/hoping it was just some kind of channel where the provider is lazily creating/sending items in the background and the receiver is picking up the items as it needs them

If it would work like that

toList()

would be lock the thread and it doesn’t sound as a good idea

Yeah, the toList() was just playing around in case the compiler worked out that the sequence was never accessed

any operation on such sequence would be block thread, not only toList()

Okay, but a launch/async would deal with that

to provide fully asynchronous sequences, all sequence operators also should be suspending to avoid problem with blocking And we have such API already it called

Channels

Okay, so I guess

sequence{}

is only useful for when calculating the next item is reasonably fast (i.e. non IO-blocking)?

Thanks for that. And with the default buffer, that would suspend so that items are only calculated when required?

by default produce uses Rendezvous channel

Ok, thanks Andrey, I’ll dive into that

and yeah, with Rendezvous channel

send

will suspend until someone consumes this value

It suspends before calculating the next value or after?

when you call

send

Right, so it’s kind of got it there ready for the next consumption

channels are “hot”