adamw

run("Eval on and back") {
  printThread *> printThread.on(ec1) *> printThread
}

/*
Outputs:

-- Eval on and back --
main
ec1-1-716083600

adamw

def run(name: String)(th: IO[_, _]): Unit = {
  println(s"-- $name --")
  new DefaultRuntime {}.unsafeRun(th)
  println()
}

run("Eval on") {
  printThread.on(ec1)
}

adamw

run("async") {
  printThread *> a *> printThread 
}

/*
Outputs:

-- async --
main
ec3-1-785992331 (async)

adamw

val a = IO.async[Unit] { cb =>
  ec3.submit(new Runnable {
    override def run(): Unit = {
      println(Thread.currentThread().getName + " (async)")
      cb(Right(()))
    }
  })
}

adamw

run("caveat 1") {
  val someEffect = IO.shift(ec1) *> printThread
  printThread *> someEffect *> printThread
}

/*
Outputs:

-- caveat 1 --
main

adamw

printThread *> printThread

adamw

run("Eval on") {
  printThread *> cs1.evalOn(ec2)(printThread) *> printThread
}

/*
Outputs:

-- Eval on --
main
ec2-1-1945604815

adamw

val cs1 = IO.contextShift(ec1)
val cs2 = IO.contextShift(ec2)

def run(name: String)(th: IO[_]): Unit = {
  println(s"-- $name --")
  th.unsafeRunSync()
  println()
}

run("Shift") {

adamw

val printThread = IO { println(Thread.currentThread().getName) }

adamw

val ec1 = ExecutionContext.fromExecutor(Executors.newCachedThreadPool(
  new NamedThreadFactory("ec1", true)))
val ec2 = ExecutionContext.fromExecutor(Executors.newCachedThreadPool(
  new NamedThreadFactory("ec2", true)))
val ec3 = Executors.newCachedThreadPool(new NamedThreadFactory("ec3", true))