racePair

open fun <A, B> racePair(ctx: CoroutineContext, ioA: IOOf<A>, ioB: IOOf<B>): IO<RacePair<ForIO, A, B>>

Race two tasks concurrently within a new IO. Race results in a winner and the other, yet to finish task running in a Fiber.

import arrow.fx.*
import arrow.fx.extensions.fx
import kotlinx.coroutines.Dispatchers

fun main(args: Array<String>) {
  //sampleStart
  val result = IO.fx {
    val racePair = !IO.racePair(Dispatchers.Default, never<Int>(), just("Hello World!"))
    racePair.fold(
      { _, _ -> "never cannot win race" },
      { _, winner -> winner }
    )
  }
  //sampleEnd

  val r = result.unsafeRunSync()
  println("Race winner result is: $r")
}

Parameters

ctx - CoroutineContext to execute the source IO on.

ioA - task to participate in the race

ioB - task to participate in the race

Return IO either Left with product of the winner’s result ioA and still running task ioB, or Right with product of running task ioA and the winner’s result ioB.

See Also

arrow.fx.typeclasses.Concurrent.raceN