Scala equivalent of C#’s extension methods?

The Pimp My Library pattern is the analogous construction:

object MyExtensions {
  implicit def richInt(i: Int) = new {
    def square = i * i
  }
}


object App extends Application {
  import MyExtensions._

  val two = 2
  println("The square of 2 is " + two.square)

}

Per @Daniel Spiewak's comments, this will avoid reflection on method invocation, aiding performance:

object MyExtensions {
  class RichInt(i: Int) {
    def square = i * i
  }
  implicit def richInt(i: Int) = new RichInt(i)
}

Since version 2.10 of Scala, it is possible to make an entire class eligible for implicit conversion

implicit class RichInt(i: Int) {
  def square = i * i
}

In addition, it is possible to avoid creating an instance of the extension type by having it extend AnyVal

implicit class RichInt(val i: Int) extends AnyVal {
  def square = i * i
}

For more information on implicit classes and AnyVal, limitations and quirks, consult the official documentation:

• http://docs.scala-lang.org/overviews/core/implicit-classes.html
• http://docs.scala-lang.org/overviews/core/value-classes.html