simple blocking future with scala

simpleFuture.scala

import scala.annotation.tailrec
import scala.concurrent._
import scala.concurrent.duration._

import ExecutionContext.Implicits.global

import java.io.EOFException
import java.lang.NumberFormatException

object Sandbox extends App {

  abstract class IOResult
  case class IOSucceeded(userInt: BigInt) extends IOResult
  case class IOFailed() extends IOResult

  override def main(args: Array[String]) = {
    print("enter an int, and I'll compute the factorial: ")

    val userIntFuture: Future[IOResult] = future {
      try { IOSucceeded(readInt()) }
      catch {
        case eof: EOFException =>
          println("EOF")
          IOFailed()
        case nfe: NumberFormatException =>
          println("NaN")
          IOFailed()
      }
    }

    userIntFuture onFailure {
      case err =>
        println("couldn't get int: " + err.getMessage())
    }

    val userIO = Await.result(userIntFuture, Duration.Inf)

    userIO match {
      case success: IOSucceeded =>
        if (success.userInt >= 0) {
          println(success.userInt + "! = " + fact(success.userInt))
        } else {
          println("factorial is undefined for " + success.userInt)
        }
        Unit
      case failure: IOFailed =>
        Unit
    }
  }

  def fact(x: BigInt) = {
    @tailrec
    def factRec(x: BigInt, acc: BigInt): BigInt = {
      if (x > 0) factRec(x - 1, acc * x)
      else return acc
    }

    factRec(x, 1)
  }
}