In order to provide status on flights, we extend the first definition of class Flight with a couple of data-items, and later by some methods that provide the status:
class FlightRoute(FlightNumber, origin, destination: var String):
scheduledDepartureTime: var TimeOfDay
scheduledArrivalTime: var TimeOfDay
-"-
class Flight(departureDate: var Date):
departureTime: var TimeOfDay
arrivalTime: var TimeOfDay:
flightTime: -> ft: var Time.Hours
ft := arrivalTime - departureTime
delayed: var Boolean
delayDeparture(newTime: var TimeOfDay):
-- this is called in case the departure is delayed
delayed := True
departureTime := newTime
delay -> period: var Time.Hours:
period := arrivalTime – scheduledArrivalTime
cancelled: var Boolean
cancel:
cancelled := True
hasArrived: var Boolean
hasTakenOff: var Boolean In the event of cancellation, the method cancel is called.
At take off, departureTime is set to the time of take off, hasTakenOff is set to True, and hasArrived is set to False. While flying the attribute arrivalTime is set based on weather condition and the landing condition of the destination airport. It is therefore assumed that this is set based on real time information from the plane. At arrival, hasArrived is set to True and hasTakenOff to False.
Status of flights are provided in two different ways, either given the origin/destination airport at a given date, or given the name of the flight route, e.g. SK1926.
The method departureStatus defined below is called with some interval before take off, to provide the text that may be displayed:
class Flight(departureDate: var Date):
-"-
departureStatus -> info: var String:
info := ("Flight " + FlightNumber + " at: " + departureDate.asString)
if cancelled :then
info := info + "is cancelled"
:else
if delayed :then
info := info + "Estimated departure time: "+
departureTime +
" expected arrival time: " +
(departureTime + flightTime)
:else
info := info + " On schedule: " +
scheduledDepartureTime.t.magnitudeThe next method is called after take off:
class Flight(departureDate: var Date):
-"-
arrivalStatus -> info: var String:
info := ("Flight " + name + " at: " + departureDate.asString)
info := info + "Departed at: "+ departureTime
if (not hasArrived) :then info := info + " expected at: " + arrivalTime :else
info := info + " arrived at: " + ArrivalTime +
" delayed: " + delayGiven the above status methods in Flight, we have three ways of selection which flights we want the status: for all flights in all flight routes of a time table, for flights departing or arriving from a given airport at a given date, or flights of a given route at a given airport and date.
Status of flights in the time table
Based upon the entries in the time table, flight status for all flights is provided by the following method:
showFlightStatus:
timeTable.scanTimeTable
fr: ref FlightRoute
fr := current
fr.scan
if (not hasTakenOff) :then
currentFlight.departureStatus.print
:else
currentFlight.arrivalStatus.print
newline The method showFlightStatus is a submethod of the method scanTimeTable in timeTable. The method scanTimeTable scans the entries list of FlightRoute objects; for each FlightRoute, held by fr, a singular method being a submethod of fr.scan scans the Flight objects of the flights list in the FlightRoute held by fr.
As described above, the method showFlightStatus is based upon a scanTimeTable method in timeTable:
timeTable: obj
entries: obj OrderList(FlightRoute)
scanTimeTable:
current: ref FlightRoute
entries.scan
this(scanTimeTable).current := current
inner(scanTimeTable)As explained before, the inner(scanTimeTable) is executed for each element in entries, and what is executed is the statements of the showFlightStatus submethod of timeTable.scanTimeTable
The above is in turn based upon a scan method of FlightRoute, scaning all the Flight objects of the list flights:
class FlightRoute(flightNumber, origin, destination: var String):
-"-
scan:
currentFlight: ref Flight
flights.scan
currentFlight := current
inner(scan)From/to a given airport, at a given date
The following method delivers the list of flights from a given airport at a given date:
fromAirport(ap: var String, d: var Date)
-> flights: ref OrderedList(Flight):
timeTable.routesFrom(ap).scan
current.flights.scan
if (current.date = d) :then
flights.insert(current)This is based upon the method routesFrom in timeTable, delivering the list of routes departing from a given airport:
timeTable: obj
-"-
routesFrom(ap: var String) -> routes: OrderedList(FlightRoute):
entries.scan
if (current.origin = ap :then
routes.insert(current)It is left as a simple exercise to make the method that delivers the list of flights to a given destination airport at a given date.
Answer:
toAirport(ap: var String, d: var Date)
-> flights: ref OrderedList(Flight):
timeTable.routesTo(ap).scan
current.flights.scan
if (current.date = d) :then
flights.insert(current)based upon:
timeTable: obj
-"-
routesTo(ap: var String) -> routes: OrderedList(FlightRoute):
entries.scan
if (current.destination = ap :then
routes.insert(current)Before the list of Flight objects delivered by these two methods are used for producing the status website, the list delivered by fromAirport should be sorted according to departure time, while the list of Flight objects delivered by toAirport should be sorted according to arrival time.
Given these two lists of Flight objects, the status website can produce the two strings delivered by the methods departureStatus and arrivalStatus.
fromAirport("OSL", Date(6, 6, 2024)).scan
current.departureStatus.print
fromAirport("OSL", Date(6, 6, 2024)).scan
current.arrivalStatus.print
fromAirport("ARR", Date(6, 6, 2024)).scan
current.departureStatus.print
fromAirport("ARR", Date(6, 6, 2024)).scan
current.arrivalStatus.print Given the flight number, airport, and a given date
The following method produces the list of flights given a certain route, from a given airport at a certain date:
onFlightNumberFrom(fn: var String, from: var String d: var Date)
-> flights: ref OrderedList(Flight):
theRoute: ref FlightRoute
theRoute := timeTable.lookupRoute(fn)
if theRoute.origin = from :then
theRoute.flights.scan
if (current.date = d) :then flights.insert(current)This is based on a simple lookupRoute in TimeTable:
timeTable: obj
entries: obj OrderList(FlightRoute)
scanTimeTable:
current: ref FlightRoute
entries.scan
this(scanTimeTable).current := current
inner(scanTimeTable)
lookupRoute(fn: var String) -> theRoute: ref FlightRoute: scanTimeTable
if current.flightNumber = fn :then
theRoute := current
leave(lookupRoute) It is left as a simple exercise to make the method that produces the list of flights given a certain route, to a given airport at a certain date:
Answer:
onFlightNumberTo(fn: var String, to: var String d: var Date)
-> flights: ref OrderedList(Flight):
theRoute: ref FlightRoute
theRoute := timeTable.lookupRoute(fn)
if theRoute.destination = to :then
theRoute.flights.scan
if (current.date = d) :then flights.insert(current)Given these two lists of Flight objects, the status website can produce the two strings delivered by the methods departureStatus and arrivalStatus.
onFlightNumberFrom("SK1926", "ARR" Date(6, 6, 2024)).scan
current.departureStatus.print
onFlightNumberTo("SK1926", "OSL" Date(6, 6, 2024)).scan
current.arrivalStatus.print 