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sealed trait HList
final case class HCons[H, T <: HList](head : H, tail : T) extends HList
case object HNil extends HList
object HList {
type ::[H, T <: HList] = HCons[H, T]
type HNil = HNil.type
implicit def hlistOps[L <: HList](l : L): AnyRef{def ::[H](h: H): HList.::[H,L]; def last(implicit last: HList.Last[L]): Unit} = new {
def ::[H](h : H) : H :: L = HCons(h, l)
def last(implicit last : Last[L]): Unit = {}
}
class Last[L <: HList]
implicit def hsingleLast[H]: HList.Last[HList.::[H,HList.HNil]] = new Last[H :: HNil]
implicit def hlistLast[H, T <: HList](implicit lt : Last[T]): HList.Last[HList.::[H,T]] = new Last[H :: T]
type III = Int :: Int :: Int :: HNil
val iii : III = 0 :: 0 :: 0 :: HNil
val l = iii.last
}
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