Scala cake pattern

gistfile1.scala

abstract class Cake {
  def top: String
  def middle: String
  def bottom: String
  override def toString = top
}
 
trait Cherry { this: Cake =>
  def top = "cherry on top of " + middle
}
 
trait Cream { this: Cake =>
  def middle = "creamy " + bottom
}
 
trait Biscuit { this: Cake =>
  def bottom = "biscuit"
}
 
(new Cake with Cherry with Cream with Biscuit).toString // “cherry on top of creamy biscuit”