shapeless_and_applicative_functor5.scala

import shapeless.{HList, ::, HNil }
import scalaz.syntax.applicative._
import scalaz.syntax.either._
import scalaz.syntax.validation._

implicit val hnilEncode: Validation[HNil] =
  Validation.createInstance( _.successNel[ValidationError]) //Yea, that's it

implicit def hlistEncoder[H, T <: HList] (
  implicit
    hEncoder: Validation[H],
    tEncoder: Validation[T]
  ): Validation[H :: T] =
   Validation.createInstance {
     case h :: t => (hEncoder.validate(h) |@| tEncoder.validate(t)){_ :: _}
   }