I'm trying to implement ```suspend fun <R> race(vararg races: suspend () -> R): R { retur...

# coroutines

[reactormonk]

I'm trying to implement

suspend fun <R> race(vararg races: suspend () -> R): R {
  return channelFlow {
    for (race in races) {
      launch { send(race()) }
     }
   }.first()
 }

for my little interpreter:

@Serializable
    sealed interface Logic: Command {
        @Serializable
        @SerialName("Race")
        // race any number of commands, will return as soon as the first one happens.
        data class Race(val commands: List<Command>): Logic
    }

But the run doesn't really make the types align:

is Command.Logic.Race -> {
            race(commands.map { command -> command.run() }.toTypedArray())
        }

[Dmitry Khalanskiy [JB]]

That's because race accepts functions, but you're passing it an array of values. Please try { command -> { command.run() } } instead of { command -> command.run() }.

[reactormonk]

Not sure how to align the syntax properly.

[Dmitry Khalanskiy [JB]]

{ command -> suspend { command.run() } } ?

[reactormonk]

That worked, had to add * for the varargs

[Jilles Soeters]

Wouldn't you want to use someting like select for this?

[Dmitry Khalanskiy [JB]]

See https://github.com/Kotlin/kotlinx.coroutines/issues/2867 for a discussion of the topic.