Factorial in Scala

Factorial.scala

object Factorial {
  implicit class LongFactorialPimp(x: Long) {
    require(x >= 0)
    def ! : Long = {
      if (x < 2) 1
      else x * ((x-1)!) // ! has the wrong precedence compared to * :(
    }
  }
  println(11!)
}

object Factorial2 {
  import math.Ordering.Implicits._
  import math.Integral.Implicits._

  implicit def fromInt[A](x: Int)(implicit i: Integral[A]): A = i.fromInt(x)

  implicit class IntegralFactorialPimp[A:Integral](x:A) {
    require(x >= fromInt(0))

    def ! : A = {
      if (x < 2) 1
      else x * ((x - fromInt(1))!)
    }
  }

  println(11!)
}