if you tell me which API is necessary to wrap, I c...

# coroutines

[pakoito]

if you tell me which API is necessary to wrap, I could take a look for the next version

[groostav]

I believe the one both me and @kingsley were thinking of is Channel, where

val x = produce { send(3), send(4), send(5) }

val mapped = x.map { it * 2 }

would provide a channel containing 6, 8 and 10, while preserving the suspend (and close) semantics

meaning, I believe, its safely implemented with

inline fun <T, R> Channel<T>.map(
    crossinline transform: (T) -> R
): Channel<R> = produce { 
  for(message in this){
    val next = recieve()
    //try-catch might be a big problem here.
    send(transform(next))
  }
  send(transform(recieve())) 
}

[groostav]

and actually, maybe this is why we wouldnt want to use channels here, because they have no error mechanism for currying exceptions

[groostav]

further, the functional programmers favourite flatMap get a little confusing here

[groostav]

Actually I think this is a fascinating point because I think its raising the question of whether we can express suspension as a monad

[pakoito]

you mean this? http://arrow-kt.io/docs/patterns/monad_comprehensions/

[pakoito]

we can express any monad as a comprehension

[pakoito]

as long as the semantics remain on the same thread

[pakoito]

the moment you jump thread you get a divide between datatypes that support asynchrony and those who don't

[pakoito]

I'm exploring that at the moment

[pakoito]

if you mean the other way around, we have the wrapper for Deferred: https://github.com/arrow-kt/arrow/blob/master/modules/effects/arrow-effects-kotlinx-coroutines/src/main/kotlin/arrow/effects/DeferredK.kt

[pakoito]

job may have a monad, we had it at some point IIRC

[pakoito]

dunno about channels tho

[groostav]

also, regarding exceptions, Our illustrious coroutine commander-in-cheif has outsmarted me. This is from the docs of produce

Uncaught exceptions in this coroutine close the channel with this exception as a cause and the resulting channel becomes failed, so that any attempt to receive from such a channel throws exception.

[groostav]

meaning you dont need special try-catch semantics on Channel.map

[kingsley]

@groostav you mean this one
https://kotlin.github.io/kotlinx.coroutines/kotlinx-coroutines-core/kotlinx.coroutines.experimental.channels/map.html