Quelle flaredispenser.vdmpp Sprache: VDM

\begin{vdm_al}
class FlareDispenser is subclass of GLOBAL

values

responseDB : map MissileType to Plan =
  {<MissileA> |-> [mk_(<FlareOneA>,900),
                   mk_(<FlareTwoA>,500),
                   mk_(<DoNothingA>,100),
                   mk_(<FlareOneA>,500)],
   <MissileB> |-> [mk_(<FlareTwoB>,500),
                   mk_(<FlareTwoB>,700)],
   <MissileC> |-> [mk_(<FlareOneC>,400),
                   mk_(<DoNothingC>,100),
                   mk_(<FlareTwoC>,400),
                   mk_(<FlareOneC>,500)] };

missilePriority : map MissileType to nat =
  {<None>     |-> 0,
   <MissileA> |-> 1,
   <MissileB> |-> 2,
   <MissileC> |-> 3 }

types

public Plan = seq of PlanStep;

public PlanStep = FlareType * Time;

instance variables

public curplan : Plan := [];
curprio        : nat := 0;
busy           : bool := false;
aperture       : Angle;
eventid        : [EventId];

operations

public FlareDispenser: nat ==> FlareDispenser
FlareDispenser(ang) ==
  aperture := ang;

public Step: () ==> ()
Step() ==
  if len curplan > 0
  then (dcl curtime : Time := World`timerRef.GetTime(),
            first : PlanStep := hd curplan,
            next : Plan := tl curplan;
        let mk_(fltp, fltime) = first in
          (if fltime <= curtime
           then (releaseFlare(eventid,fltp,fltime,curtime);
                 curplan := next;
                 if len next = 0
                 then (curprio := 0;
                       busy := false ) )
           )
    );

pure public GetAngle: () ==> nat
GetAngle() ==
  return aperture;

public addThreat: EventId * MissileType * Time ==> ()
addThreat (evid, pmt, ptime) ==
  if missilePriority(pmt) > curprio
  then (dcl newplan : Plan :=  [],
            newtime : Time := ptime;
        -- construct an absolute time plan
        for mk_(fltp, fltime) in responseDB(pmt) do
          (newplan := newplan ^ [mk_ (fltp, newtime)];
           newtime := newtime + fltime );
        -- immediately release the first action
        def mk_(fltp, fltime) = hd newplan;
            t = World`timerRef.GetTime() in
          releaseFlare(evid,fltp,fltime,t);
        -- store the rest of the plan
        curplan := tl newplan;
        eventid := evid;
        curprio := missilePriority(pmt);
        busy := true )
pre pmt in set dom missilePriority and
    pmt in set dom responseDB;

private releaseFlare: EventId * FlareType * Time * Time ==> ()
releaseFlare (evid,pfltp, pt1, pt2) ==
  World`env.handleEvent(evid,pfltp,aperture,pt1,pt2);

public isFinished: () ==> bool
isFinished () ==
  return not busy;

pure public getAperture: () ==> Angle * Angle
getAperture () == return mk_(0,0);

end FlareDispenser
\end{vdm_al}

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