我如何阻止先决条件在 ADA Spark 的以下示例中失败

问题描述

对于一个项目，我目前正在尝试为虚拟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。我已经为我想使用的飞机组件建模，在主文件中做了一些测试以检查组件是否按预期工作，一切都很好，现在我要为函数添加前置和后置条件以确保我的飞机超级安全的。其中一项安全措施是确保在飞机处于牵引状态时发动机不能打开，反之亦然，在发动机处于开启状态时切换到牵引状态。

我将引擎建模为一个高度复杂的记录，具有一个属性，类型为 OnOff，它采用值 On 或 Off 之一。请注意，我计划扩展属性，因此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;

飞机文件中的过程 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;

平面作为变量传入，因此我可以检查前后条件的各种属性，但我收到警告消息，我不确定如何解决。

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.

这里是主文件中平面的初始化

AirForceOne : Plane := (
   engine1 => (isOn => Off),engine2 => (isOn => Off),litresPerMile => 5,gearOfLanding => (isExtended => Extended),doorPax1 => (isClosed => Closed,isLocked => Unlocked),doorPax2 => (isClosed => Closed,doorServ1 => (isClosed => Closed,doorServ2  => (isClosed => Closed,doorCockpit => (isClosed => Closed,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。我认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。

解决方法

Switchonengine 的目的是改变飞机的状态。编写它来改变引擎的状态会使事情复杂化。

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);