I'm searching a way to zip two HList together. The first one is generated from a case class converted in its generic representation, and the second one is defined manually as an HList of Nat.
As a result, I expect a tuple (or 2-members HList) with one field from the case class, and the Nat associated.
The goal is to create a "customizable" ZipWithIndex.
def derive[A, I <: HList, R <: HList, Z <: HList](implicit
gen: Generic.Aux[A, R],
zipper: Zip.Aux[R, I, Z],
enc: Lazy[Encoder[Z]])(a: A): Deriver[A] = {
val genRepr = gen.to(A)
val zipped = zip(genRepr :: ??? :: HNil)
enc.value(zipped)
}
case class Foo(a: String, b: String, c: String)
derive[Foo, Nat._1 :: Nat._3 :: Nat.7 :: HNil]
The result will have to match an encoderTuple[H, N <: Nat, T <: HList]: Encoder[(H, N) :: T] or and encoderHList[H, N <: Nat, T <: HList]: Encoder[(H::N::HNil) :: T].