1) if you don't write your own collection you don't need CanBuildFrom 2) What is so hard to understand about CanBuildFrom[-From, -Elem, +To]. It's an object tha

1) if you don't write your own collection you don't need CanBuildFrom 2) What is so hard to understand about CanBuildFrom[-From, -Elem, +To]. It's an object that will return a builder for a collection: See http://www.dotkam.com/2012/05/08/scala-fun-with-canbuildfrom/ http://www.dotkam.com/2012/05/08/scala-fun-with-canbuildfrom... for an explanation. In Java one would call it a Factory ;-)