anchor.diff:                  | Min _          -> "specify the minimum time for routes"
                   | Max _          -> "specify the maximum time for routes"
                   | ArriveBefore _ -> "set the local time that routes must arrive by"
  +                | Arrival _      -> "set the arrival airport"
                   | DepCont _      -> "set the continent for the departure airport"
                   | ArrCont _      -> "set the continent for the arrival airport"
                   | DepType _      -> "set the type of airport for the departure"
  
positive.code:     | [<PrintLabels>] Min          of hours:string
      | [<PrintLabels>] Max          of hours:string
      | [<PrintLabels>] ArriveBefore of hour:string
      | DepCont      of string
      | ArrCont      of string
      | DepType      of string
      | ArrType      of string
      | Sort         of string
      with
          interface IArgParserTemplate with
              member s.Usage =
  
negative.code:             | Min          (Time t)   -> Filter.MinTime t            |> Some
              | Max          (Time t)   -> Filter.MaxTime t            |> Some
              | ArriveBefore (Time t)   -> Filter.ArriveBefore t       |> Some
              | Arrival icao            -> Filter.ArrivalAirport icao  |> Some
              | DepCont c               -> Filter.DepartureContinent c |> Some
              | ArrCont c               -> Filter.ArrivalContinent c   |> Some
              | DepType (AirportType t) -> Filter.DepartureType t      |> Some
  