poly functions / map over HLists in shapeless

poly.scala

def publish = {
  val a AEvent("a")
  val b = BEvent("b")
  a :: b :: a :: HNil
}

def use = {
  object handler extends Poly1 {
    implicit def caseA = at[AEvent](_.toString)
    implicit def caseB = at[BEvent](_.toString)
  }
  publish.map(handler)
}