Non-homogeneous tree

gistfile1.scala

package socco

abstract class SoccoTree(val children:List[SoccoTree]) extends Seq[SoccoTree] with SoccoNode[SoccoTree] {
  def apply(n:Int) = children(n)
  def iterator = children.iterator
  def length = children.length
//  def add(t:SoccoTree)(implicit builder:SoccoTreeBuilder[B]) = builder.build(this.asInstanceOf[B], children :+ t)
}
trait SoccoNode[B <: SoccoTree] {
  def soccoCompanion:SoccoTreeCompanion[B]
}
trait SoccoTreeCompanion[A <: SoccoTree] {
  implicit val builder:SoccoTreeBuilder[A]
}
trait SoccoTreeBuilder[A <: SoccoTree] {
  def build(node:A, children:List[SoccoTree]):A
}


object Directory extends SoccoTreeCompanion[Directory] {
  def apply(name:String) = new Directory(name,List())
  implicit val builder = new SoccoTreeBuilder[Directory] {
    def build(node:Directory, children:List[SoccoTree]) = new Directory(node.name, children)
  }
}
class Directory(val name:String,
                    val _children:List[SoccoTree]) extends SoccoTree(_children) with SoccoNode[Directory] {
  def soccoCompanion = Directory
}