apply.scala

  import cats.syntax.all._
  import cats.data._
  import cats._

  val f = Validated.invalid[Eval[String], Eval[Int]](Eval.always { println("eval fail"); "oops" })
  val s = Validated.valid[Eval[String], Eval[Int]](Eval.always { println("eval succ"); 1 })

  val combine: Validated[Eval[String], Eval[Int]] = f *> s

  val res = combine.bimap(_.value, _.value) match {
    case Validated.Valid(a)   => println(a)
    case Validated.Invalid(e) => println(e)
  }

compare to

 val f: Either[Eval[String], Eval[Int]] = Left[Eval[String], Eval[Int]](Eval.always { println("eval fail"); "oops" })
  val s: Either[Eval[String], Eval[Int]] = Right[Eval[String], Eval[Int]](Eval.always { println("eval succ"); 1 })

  val combine = f >> s

  val res = combine.bimap(_.value, _.value) match {
    case Left(a)  => println(a)
    case Right(e) => println(e)
  }

f and s both evaluated in Validated. only f is evaluated in Either