hlist

I would like to transform an HList type parameter to a nested Map-type, e.g. Int :: String :: String :: HNil should become Map[Int, Map[String, Map[String, T]]]] where T would be another type parameter of the same function, like: def somedef[T, L <: HList](t: T)(implicit f: ???): f.Out where f.Out is T in case of HNil or a nested Map-structure with dept L.size Is there any way this can be done? I'm not aware of a standard thing to do such a transformation, but you could roll out your custom converter in the same way as various HList ops (like map ) are implemented inside shapeless (see trait

I am trying to transform the following HList Some(C(15)) :: None :: Some(B(55)) :: None :: Some(A(195)) :: HNil to C(15) :: B(55) :: A(195) :: HNil Here is what I have at the moment : import shapeless._ case class A(value: Int) case class B(value: Int) case class C(value: Int) trait folderLP extends Poly2 { implicit def default[T, L <: HList] = at[T, L]((acc, t) => acc) } object folder extends folderLP { implicit def none[T, L <: HList] = at[None.type, L]((t, acc) => acc) implicit def someDiameter[T, L <: HList] = at[Some[C], L]((t, acc) => t.get :: acc) implicit def someRatio[T, L <: HList] =

This does not compile and I do not understand why: import shapeless._ import poly._ object option extends (Option ~> List) { def apply[T](t: Option[T]) = t.toList } val simple = Some(1) :: Some("hello") :: Some(true) :: HNil val opts: List[Int] :: List[String] :: List[Boolean] :: HNil = simple map option This is somewhat surprising, because this does compile: import shapeless._ import poly._ object choose extends (Set ~> Option) { def apply[T](s: Set[T]) = s.headOption } val sets = Set(1) :: Set("foo") :: HNil val opts: Option[Int] :: Option[String] :: HNil = sets map choose The problem is

I'm using libraryDependencies += "com.chuusai" %% "shapeless" % "2.2.4" Currently i have model HList types like sealed trait Section case class Header(...) extends Section case class Customer(...) extends Section case class Supplier(...) extends Section case class Tech(...) extends Section type ContractView = Header :: (Customer :: Supplier :: HNil) :: Tech :: HNil In my user code, i'd like to filter technical sections that are not supposed to view using foldRight as proposed in this answer : trait collectAllRF extends Poly2 { implicit def atAny[L <: HList, X] = at[X, L](_ :: _) } object