trait Obs[+A] { def value: A }
 
object Obs {
  import shapeless._, poly._, ops.hlist.Mapper, ops.function.FnToProduct
 
  object values extends (Obs ~> Id) {
    def apply[T](t: Obs[T]) = t.value
  }
 
  def calculate[T, V <: HList, L <: HList, F, Z](obss: T)(f: F)(implicit
    gen: Generic.Aux[T, L],
    mapper: Mapper.Aux[values.type, L, V],
    ftp: FnToProduct.Aux[F, V => Z]
  ): Z = ftp(f)(mapper.apply(gen.to(obss)))
}
 
object ObsExample {
  import Obs._
 
  val obs1: Obs[Double] = new Obs[Double] { val value = 10.0 }
  val obs2: Obs[Option[Int]] = new Obs[Option[Int]] { val value = Some(1) }
 
  def func(d: Double, i: Option[Int]) = d + i.getOrElse(0).toDouble

  println(calculate(obs1, obs2)(func _))
}