Attributed Things

object Attribute {

  
  case class Attributed[Thing, Attribute](val thing: Thing, val attributes: Set[Attribute] = Set[Attribute]()) {
  
    /** Add an attribute. */
    def +(a: Attribute) = copy(attributes = attributes+a)
    
    /** Change attributes for which the partial function is defined. */
    def change(pf: PartialFunction[Attribute,Attribute]) =
      new Attributed(thing, attributes.map { pf orElse {case v => v} })
  }
  

  val as1 = Attributed[String,String]("rofl")
  val as2 = as1 + "silly" + "funny" + "derp"
  val as3 = as2 change { case "derp" => "herp" }
  
}