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Datei: Bus.vdmpp Sprache: VDM

Original von: VDM^©

class Bus

instance variables
  seats : set of Passenger;
  inv card seats <= Config`BusCapacity;

  --bus line number
  line : nat;

  -- the route of road the bus is moving along
  route : seq of Road;
  -- what roads are left in the current pass of the route
  curRoute : seq of Road;
  -- where are we heading
  nextWP : Waypoint;
  -- what road are we currently on
  currentRoad : Road;
  --waypoints passed by the bus
  wps : seq of Waypoint;

operations
  public Bus : nat * seq of Road * seq of Waypoint ==> Bus
  Bus(linenumber, busroute, waypoints)==
  (
   line := linenumber;
   route := busroute;
   curRoute := busroute;
   nextWP := hd waypoints;

   wps := waypoints;
   seats := {};
  )
  pre len waypoints > 1 --ensure bus has somewhere to go
  and waypoints <> [];

  public GetOn : set of Passenger ==> ()
  GetOn(ps) ==
  (
   seats := seats union ps;
   World`graphics.busPassengerCountChanged(line, card seats);
  )
  pre card seats + card ps <= Config`BusCapacity;

  public GotOff : set of Passenger ==> ()
  GotOff(p) ==
  (
   seats := seats \ p;
   World`graphics.busPassengerCountChanged(line, card seats);
  )
  pre p inter seats <> {};

  pure public GetWaypoints : () ==> seq of Waypoint
  GetWaypoints()==
   return wps;

  pure public GetStops : () ==> seq of Busstop
  GetStops()==
   return [wps(i) | i in set inds wps & wps(i).IsStop() ];


  private NextWaypoint : () ==> Waypoint
  NextWaypoint()==
  (
   --start route over
   if(len curRoute = 0) then
     curRoute := route;

   --next road
   let nextRoad = hd curRoute in
   (
    --move along route
    curRoute := tl curRoute;
    --what road are we on
    currentRoad := nextRoad;
    -- update waypoints
    let currentWp = nextWP  in
    (
     nextWP := currentRoad.OppositeEnd(currentWp);
     return currentWp;
    )
   );
  );

  --functionality to ensure thread start
  public WaitForThreadStart : () ==> ()
  WaitForThreadStart() == skip;

  private ThreadStarted : () ==> ()
  ThreadStarted() == skip;

sync
  per GetOn => card seats < Config`BusCapacity;
  per WaitForThreadStart => #fin(ThreadStarted) > 0

thread
(
  dcl passGettingOn : set of Passenger;
  ThreadStarted();
  let - = NextWaypoint() in skip; --prevent return

  --loop which moves bus along route, and lets passengers on and off at stops
  while true do
  (
   Printer`OutWithTS("%Bus " ^ Printer`natToString(line) ^ ": running on " ^
         VDMUtil`val2seq_of_char[Road`RoadNumber](currentRoad.GetRoadNumber()) ^
         " with length " ^ Printer`natToString(currentRoad.GetLength()) ^ " and speedlimit " ^
          Printer`natToString(currentRoad.GetSpeedLimit()) ^
          " Next: " ^ VDMUtil`val2seq_of_char[Waypoint`WaypointsEnum](nextWP.GetId()) ^
          " Time: " ^ Printer`natToString(currentRoad.GetTimePenalty())
       );

   World`graphics.busInRouteTo(line,
    VDMUtil`val2seq_of_char[Road`RoadNumber](currentRoad.GetRoadNumber()),
    VDMUtil`val2seq_of_char[Waypoint`WaypointsEnum](nextWP.GetId()),
    currentRoad.GetTimePenalty());

   --add to penalty for moving along road
   World`timerRef.WaitRelative(currentRoad.GetTimePenalty());
      World`timerRef.NotifyAll();
      World`timerRef.Awake();

   --next on bus route
   let next = NextWaypoint() in
   (
    Printer`OutWithTS("%Bus " ^ Printer`natToString(line) ^
    " arrived at " ^
    VDMUtil`val2seq_of_char[Waypoint`WaypointsEnum](next.GetId()));

    let nextId = next.GetId() in
    (
     --let passengers in at central station if
     --their destination is on the bus' route
     if nextId = <Central> then
     (
      --bus returned with passengers; in the current model this should not be possible
      --if(seats <> {}) then exit "Bus returned with passengers";

      let central : Busstop = next in
      (
       --find passengers for bus
       let potentialPassengers : set of Passenger = central.GetWaitingOn(wps) in
       (
        if(card potentialPassengers > 0) then
        (
         --count available sets in bus
         if((Config`BusCapacity - card seats) < card potentialPassengers) then
          --not room for all, select some
          passGettingOn := SelectSubset(potentialPassengers, Config`BusCapacity - card seats)
         else
          passGettingOn := potentialPassengers;

         -- leave busstop and enter bus seats
         central.PassengerLeft(passGettingOn);
         GetOn(passGettingOn);
         for all p in set passGettingOn do p.GotOnBus();

         Printer`OutWithTS("%Bus " ^ Printer`natToString(line) ^ ": " ^
          Printer`natToString(card passGettingOn) ^ " got on");

         --add to time penalty for stopping
         World`graphics.busStopping(line);
         World`timerRef.WaitRelative(3);
            World`timerRef.NotifyAll();
            World`timerRef.Awake();
        )
       );
      );
     );

     -- let passengers off at their destination
     let gettingOff = { p | p in set seats & p.GetDestination() = next} in
     (
      if(card gettingOff > 0) then
      (
       GotOff(gettingOff);
       Printer`OutWithTS("%Bus " ^ Printer`natToString(line) ^ ": " ^
        Printer`natToString(card gettingOff) ^ " got off");

       World`env.TransportedPassengers(card gettingOff);

       --add to time penalty for stopping
       World`graphics.busStopping(line);
       World`timerRef.WaitRelative(3);
          World`timerRef.NotifyAll();
          World`timerRef.Awake();
      );
     );
    );
   );

  );
);

operations
  pure private SelectSubset : set of Passenger * nat ==> set of Passenger
  SelectSubset(ps, limit)==
  (
   --base case
   if limit = 0 then
    return {};

   --smaller than limit, return
   if card ps <= limit then
    return ps;

   --recusive
   let sub in set ps in
     return {sub} union SelectSubset(ps \ {sub}, limit -1);
  )

end Bus

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