custom scala set collection example.

gistfile1.scala

// ============================= NamedCustomSet ===================================
object NamedCustomSet {
  
  def apply[A](name:String, s:A*) = new NamedCustomSet(name, s.toSet)
  
  implicit def canBuildFrom[A,B]: CanBuildFrom[NamedCustomSet[B], A, NamedCustomSet[A]] = 
    new CanBuildFrom[NamedCustomSet[B], A, NamedCustomSet[A]] {
      def apply(from: NamedCustomSet[B]) = newBuilder(from.name)
      def apply() = newBuilder
  }
  def empty[A] = new NamedCustomSet[A]("empty")
  
  def newBuilder[A]: Builder[A, NamedCustomSet[A]] =  
    new SetBuilder[A, NamedCustomSet[A]](empty)
    
  def newBuilder[A](name:String): Builder[A, NamedCustomSet[A]] =  
    new SetBuilder[A, NamedCustomSet[A]](new NamedCustomSet[A](name))
}


class NamedCustomSet[A](val name:String, protected val backend:Set[A]=Set.empty[A])
  extends Set[A]
  with SetLike[A, NamedCustomSet[A]] {
  
  def contains(key: A): Boolean = backend.contains(key)
  def iterator: Iterator[A] = backend.iterator
  def +(elem: A)  = if ( contains(elem)) this else new NamedCustomSet(name, backend+elem)
  def -(elem: A)  = if (!contains(elem)) this else new NamedCustomSet(name, backend-elem)
  override def empty = NamedCustomSet.empty
  override def toString = {
    val content = size match {
      case 0 => ""
      case x if x < 10 => mkString(",",",","")
      case _ => take(9).mkString(",",",","...")
    }
    "NamedCustomSet("+name+content+")"
  }
}