anchor.diff:      | Success _   -> ()
       | Failure msg -> eprintfn "Failure during route processing: %s" msg
   
  -[<EntryPoint>]
  -let main args =
  +let checkAndupdateAirportData () =
       match Airport.isOldDataFile airportDataPath with
       | true ->
           printfn "Airport data out of date. Updating.."
  
positive.code:         | Failure msg -> eprintfn "Error updating airport data: %s" msg
      | false -> ()
  
      args
      |> readArguments
      |> Option.iter processAirports
  
      0
negative.code: let readArguments args =
      let parser = ArgumentParser.Create<CmdArguments>()
      try
          parser.Parse(args) |> Some
      with
      | :? ArgumentException ->
          parser.Usage() |> eprintfn "Usage:%s"
  