ada - 如何阻止 ADA Spark 中的以下示例中的先决条件失败

Question

对于一个项目，我目前正在尝试为一架假想的飞机编写一个迷你飞行员辅助系统。任务是学习 Ada Spark，而不是航空电子设备。我已经对我希望使用的飞机组件进行了建模，在主文件中进行了一些测试以检查组件是否按预期工作，一切都很好，现在我要向函数添加前置和后置条件，以确保我的飞机 super 安全的。其中一项安全措施是确保在飞机牵引时无法启动发动机，反之亦然，在发动机启动时切换到牵引。

我将引擎建模为高度复杂的记录，具有一个属性，类型为 OnOff，它采用 On 或 Off 值之一。请注意，我计划扩展属性，因此它不会保留单一属性记录。

这是引擎规范文件

package engines with SPARK_Mode
is

type OnOff is (On, Off);
type Engine is record
  isOn: OnOff;
end record;


procedure switchOn (x : in out Engine);
procedure switchOff (x : in out Engine);

end engines;

我的飞机是这样组装的:

   type Plane is record
     engine1: Engine;
     engine2: Engine;
     gearOfLanding: LandingGear;
     doorPax1, doorPax2, doorServ1, doorServ2, 
     doorCockpit: Door;
     panelOfReadings: ReadingsPanel;
     panelOfAlerts: AlertsPanel;
     planOfFlight: FlightPlan;
     speedLimits: SpeedLimit;
     altitudeLimits: AltitudeLimit;
     attitudeLimits: AttitudeLimit; 
     litresPerMile: Integer;
     fuelTank1: FuelTank;
  end record;

planes 文件中的过程 switchOnEngine 将引擎作为输入，并从引擎文件中调用 switchOn。这是规范，下面是正文:

  procedure switchOnEngine (x : in out Engine; y : in Plane) with
    Pre => y.panelOfReadings.mode /= Tow,
    Post => x = (isOn => On) and y.panelOfReadings.mode /= Tow;



  procedure switchOnEngine (x : in out Engine; y : in Plane)
  is
  begin
      switchOn(x);
  
  end switchOnEngine;

飞机作为变量传入，因此我可以检查前置条件和后置条件的各种属性，但我收到警告消息，但不确定如何解决。

precondition might fail
cannot prove y.panelOfReadings.mode /= Tow e.g when .......mode =>Tow

以下行也从我控制飞机的主文件中给出错误

switchOnEngine(AirForceOne.engine1, AirForceOne);

formal parameters x and y are aliased, and this is being marked as a 'high' priority warning.

这是主文件中飞机的初始化

AirForceOne : Plane := (
   engine1 => (isOn => Off),
   engine2 => (isOn => Off),
   litresPerMile => 5,
   gearOfLanding => (isExtended => Extended),
   doorPax1 => (isClosed => Closed, isLocked => Unlocked),
   doorPax2 => (isClosed => Closed, isLocked => Unlocked),
   doorServ1 => (isClosed => Closed, isLocked => Unlocked),
   doorServ2  => (isClosed => Closed, isLocked => Unlocked),
   doorCockpit => (isClosed => Closed, isLocked => Unlocked),
   fuelTank1 => (capacity=>26000, currentFuel=>26000),
   planOfFlight => (distFromDest => 1500),
   panelOfReadings =>
       (mode => Tow,
        currentSpeed => 0,
        altitud => 0,
        attitud =>
            (currentPitch=>0,
             currentRoll =>0)
       ),
   panelOfAlerts =>
       (approachingStallSpeed => Off,
        unRestrictedSpeed => Off,
        withinLandingSpdRange => Off,
        withinOptCruiseAlt => Off,
        withinOptCruiseSpeed => Off,
        takeoffSpeedReached => Off,
        fuelStatus => Off,
        maxPitchAngleExceeded => Off,
        maxRollAngleExceeded => Off),
   speedLimits =>
       (minLanding => 180,
        maxLanding => 200,
        minStall => 110,
        minTakeoff => 130,
        maxRestricted => 300,
        maxGroundMode => 10),
   altitudeLimits =>
       (minFlight => 500,
        maxFlight => 41000,
        optCruiseAlt => 36000,
        maxRestrictedSpeed => 10000,
        maxInitiateFlareMode => 100),
   attitudeLimits =>
       (maxRoll => 30,
        maxPitch => 30,
        minRoll => -30,
        minPitch => -30)
 );

任何帮助都会很棒。我以为在前提条件下建议飞机不能被拖走就足够了，但似乎还不够。

Answer 1

Switchonengine的目的是改变飞机的状态。编写它来改变引擎的状态会让事情变得复杂。

Max_Engines : constant := 100; -- The Lillium jet has 36, so I hope this is enough

type Engine_Num is range 1 .. Max_Engines;

type Engine_Info is ...

type Engine_Map is array (Engine_Num range <>) of Engine_Info with
   Dynamic_Predicate => Engine_Map'First = 1;

type Plane_Info (Num_Engines : Engine_Num) is record
   Engine : Engine_Map (1 .. Num_Engines);
   ...

procedure Turn_On (Engine : in Engine_Num; Plane : in out Plane_Info) with
   Pre => Engine in 1 .. Plane.Num_Engines and then
          (not Running (Plane.Engine (Engine) ) and not Under_Tow (Plane),
   Post => Running (Plane.Engine (Engine) );

Air_Force_One : Plane_Info (Num_Engines => 4);