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3.4.2 Variable Examples

3.4.2.1 Simple state machine where the state is captured in a variable of enum type

This example shows a simple state machine for a siren where the state is captured in an enumeration. 

interface Siren
{
  in void turnOn();
  in void turnOff();
  behaviour
  {
    enum State { SirenOff, SirenOn }; // type declaration
    State state = State.SirenOff;     // variable declaration
    [state.SirenOff] // if the Siren is off, only allow to turn it on
    {
      on turnOn:  state = State.SirenOn;
      on turnOff: illegal;
    }
    [state.SirenOn] // if the Siren is on, only allow to turn it off
    {
      on turnOff: state = State.SirenOff;
      on turnOn:  illegal;
    }
  }
}

3.4.2.2 Simple state machine where the state is captured in a boolean type

This example shows a simple state machine for a siren where the state is captured in a variable of boolean type 

interface Siren
{
  in void turnOn();
  in void turnOff();
  behaviour
  {
    bool SirenOn = false;
    [SirenOn] // if the Siren is on, only allow to turn it off
    {
      on turnOff: SirenOn = false;
      on turnOn:  illegal;
    }
    [otherwise]
    {
      on turnOn:  SirenOn = true;
      on turnOff: illegal;
    }
  }
}

3.4.2.3 Limited retrying activation of a device using a variable of integer type

This example shows how a counter based on an integer type can be used to limit retrying activation of a device. 

component AlarmSystemComp
{
  provides AlarmSystem alarmSystem;
  requires Sensor sensor;
  requires Siren siren;
  behaviour
  {
    enum State
    {
      NotActivated,
      Activated_Idle,
      Activated_AlarmMode,
      Deactivating
    };
    subint myInt {0..10};                 // myInt is defined as integer within the range 0-10
    myInt counter = 0;                    // myInt is initialised with value 0.
    State state = State.NotActivated;
    void activating(Sensor.Values value)  // recursive function to activate the sensor, it will retry 10 times.
    {
      if (value == Sensor.Values.OK)
      {
        reply(AlarmSystem.Values.Ok);
        state = State.Activated_Idle;
      }
      else
      {
        if (counter <10)
          {
          counter = counter + 1;
          Sensor.Values val = Sensor.Activate();
          activating(val);                 // try again
          }
        else
          {
          reply(AlarmSystem.Values.Failed);
          }
       }
    }
    [state.NotActivated]
    {
      on alarmSystem.SwitchOn():
      {
        Sensor.Values val = Sensor.Activate();
        activating(val);                    // call the activation function
      }
      on alarmSystem.SwitchOff(), sensor.DetectedMovement(), sensor.Deactivated():
      {
        illegal;
      }
    }
    /* ...  */
    /* ...  */
  }
}

See also:

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