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travisbrown/Command.scala

Created April 15, 2015 21:49
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Command.scala
import scalaz._, Free.Trampoline, Scalaz._
sealed trait Command[T]
case class Wait(ms: Long) extends Command[Unit]
case object Evaluator extends (Command ~> Trampoline) {
override def apply[T](cmd: Command[T]) = cmd match {
case Wait(t) => Trampoline.done(Thread.sleep(t))
}
}
object Api {
def sleep(ms: Long): Free.FreeC[Command, Unit] = Free.liftFC(Wait(ms))
}
val sleep: Free.FreeC[Command, Unit] =
Api.sleep(1).flatMap { _ => sleep }
Free.runFC(sleep)(Evaluator).run
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