ScalaValidationHelper.scala

case class Transformer[From, To](input: List[From], f: From => To) {
  import scala.util.{Try, Success, Failure}

  lazy val transformedWithIndex: List[(Try[To], Int)] =
    input map { l => Try ( f(l) ) } zipWithIndex

  def failuresWithIndex =
    transformedWithIndex.filter { case (v, i) => v.isFailure }

  lazy val failuresExist: Boolean =
    ! failuresWithIndex.isEmpty

  def successfulOnly: List[To] =
    for {
      (e, _) <- transformedWithIndex
      value <- e.toOption
    } yield value
}

val lines = List("12", "13", "13a", "14", "foo")

val res = Transformer(lines, (l: String) => l.toInt)

println("FAILURES EXIST?: " + res.failuresExist)
println("PARSED LINES WITH INDEX: " + res.transformedWithIndex)
println("SUCCESSFUL ONLY: " + res.successfulOnly)

/*
Prints:

FAILURES EXIST?: true

PARSED LINES WITH INDEX: List((Success(12),0), (Success(13),1), (Failure(java.lang.NumberFormatException: For input string: "13a"),2), (Success(14),3), (Failure(java.lang.NumberFormatException: For input string: "foo"),4))

SUCCESSFUL ONLY: List(12, 13, 14)
*/