validation.scala

def validateAmmo(ammo: => Long): Validation[List[String]] = {
  if (ammo > 0) Success[List[String]]()
  else Failure(List("Negative ammo"))
}

def validateName(name: => String): Validation[List[String]] = {
  if (!name.isEmpty) Success[List[String]]()
  else Failure(List("Empty Name"))
}