// represents a filter function that take a collection of cabs, filters and returns the result
  type Filter = List[Cab] => List[Cab]

/* a simple filter to filter cabs based on source and destination, */
  def matchRoutes(source: Source, destination: Destination): Filter = {
    cabs: List[Cab] => cabs.filter(c => c.finalDestination == destination && isWithinRange(c.currentLocation, source))
  }

  def isWithinRange(cabLoc: Location, myLoc: Location) = true

  /* a simple filter to filter cabs based on service type - pool, premier, etc, */
  def matchClass(typName: String): Filter = {
    cabs: List[Cab] => cabs.filter(_.typ.equalsIgnoreCase(typName))
  }

  /* a simple filter to filter cabs based on some kind of promotion */
  def matchPromotionCabs: Filter = {
    cabs: List[Cab] => cabs.filter(_.isOnPromotion)
  }

  /*  a long laborious process of matching the best cabs based on multitude of factors
  *  such as driver ratings, user ratings, co-passenger ratings, traffic conditions, etc
  * */
  def matchSeats(numOfSeats: Int): Filter = {
    cabs: List[Cab] => cabs.filter(_.seatsAvlbl == numOfSeats)
  }

  def matchDistanceToPickUp(here: Location, dis: Double): Filter = {
    cabs: List[Cab] => cabs.filter(_.distanceFromHere(here) == dis)
  }

  def matchTimeToDrop(here: Location, time: Int): Filter = {
    cabs: List[Cab] => cabs.filter(_.timeToDrop(here) <= time)
  }