Speculation.scala

package speculation

import java.util.concurrent.{ Callable, ExecutorService, Future }

class Speculation(val executor: ExecutorService, val mayInterruptIfRunning: Boolean) {
  def spec[A,B](guess: => A)(f: A => B)(actual: => A): B = {
    val g = executor.submit(new Callable[A] {
      def call = guess
    })
    val speculation = executor.submit(new Callable[B] {
      def call = f(g.get())
    })
    val a = actual
    val guessed = g.get()
    if (a == guessed) {
      speculation.get()
    } else {
      speculation.cancel(mayInterruptIfRunning)
      f(actual)
    }
  }
}