My implementation of a post on the Daily Scala

MooCowCustColl.scala

import scala.collection._
import scala.collection.generic._

//
// Simple example of custom Traversable that is provided by the Daily Scala:
// http://daily-scala.blogspot.com/2010/04/creating-custom-traversable.html
//

class MooCow[A](seq: A*) extends Traversable[A] with GenericTraversableTemplate[A, MooCow] with TraversableLike[A, MooCow[A]]{
    override def companion = MooCow
    def foreach[U](f: A => U) = seq.reverse.foreach(f)
}

// These are minimal implementations as indicated by the sources.
object MooCow extends TraversableFactory[MooCow] {
    implicit def canBuildFrom[A]: CanBuildFrom[Coll, A, MooCow[A]] = new GenericCanBuildFrom[A]

    def newBuilder[A] = new scala.collection.mutable.LazyBuilder[A, MooCow[A]] {
        def result = {
            val data = parts.foldLeft(List[A]()){(l,n) => l ++ n}
            new MooCow(data:_*)
        }
    }
}