CompositionPostInline

FirstAttemptInline.scala

// first attempt: let's just write it down and make the compiler happy:
def processRequest(a: A): Future[Result] = f1(a).flatMap {
  case Right(b) => f2(b).flatMap {
    case Right(c) => f3(c).flatMap {
      case Right(d) => 
        f4(d).map(either => either.getOrElse(either.left.get))
      case Left(f) => Future.successful(f) // we "satisfy" Future.flatMap by wrapping
                                           // the left result with a successful future
    }
    case Left(f) => Future.successful(f) // and again..
  }
  case Left(f) => Future.successful(f) // and again
}