LSD Specification for a Cat Flap

/*******************************************************************
        file    :       catflap.lsd
        date    :       1990
        author  :       S.Yung
        notes   :       Description of agents for a `catflap' system
********************************************************************/

AGENT flap() {
STATE
        (int)   lflap = 5       // the length of the flap
        (bool)  switch = true   // whether the electronic lock is operating
        (int)   fourWayLock = 0 // fourWayLock =
                                //    0 - the cat can pass through from either direction
                                //    1 - the cat can go out only
                                //    2 - the cat can go in only
                                //    3 - the cat cannot pass through from either direction
        (int)   Radius = 10     // range of the detector of the electronic lock
STATE-HANDLE
        (int)   angle = 0       // the inclination of the flap
STATE-ORACLE    
        (bool)  pushOut
        (bool)  pushIn
STATE
        (int)   pos
DERIVATE-STATE
        (bool) elecLock = abs(pos) > Radius AND switch
        (bool) canPushOut = angle != 0 OR !elecLock AND (fourWayLock == 0 OR fourWayLock == 1)
        (bool) canPushIn = angle != 0 OR !elecLock AND (fourWayLock == 0 OR fourWayLock == 2)
PROTOCOL
        pushOut AND canPushOut -> angle = |angle| + 1
        pushIn AND canPushIn -> angle = |angle| - 1
        !pushOut AND !pushIn AND angle > 0 -> angle = |angle| - 1
        !pushOut AND !pushIn AND angle < 0 -> angle = |angle| + 1
}




// the 4-way-lock is rotated only when the flap is closed
AGENT man() {
HANDLE-ORACLE
        (bool)  switch
        (int)   fourWayLock
ORACLE
        (int)   angle
PROTOCOL
        switch == false -> switch = true
        switch == true -> switch = false
        angle == 0 AND fourWayLock != 0 -> fourWayLock = 0
        angle == 0 AND fourWayLock != 1 -> fourWayLock = 1
        angle == 0 AND fourWayLock != 2 -> fourWayLock = 2
        angle == 0 AND fourWayLock != 3 -> fourWayLock = 3
} 




AGENT cat() {
STATE-HANDLE
        (int)   height = 2      // height of the cat
        (int)   pos             // pos > 0 - outside the house; < 0 inside the house
        (int)   intention       // intention =
                                //     1 - is going out
                                //     0 - is staying put
                                //    -1 - is coming in
ORACLE
        (int)   lflap, angle
DERIVATE-STATE
        (bool) obstructOut = lflap * tan(angle) > pos > (lflap - height) * tan(angle) - 1
        (bool) obstructIn = lflap * tan(angle) < pos < (lflap - height) * tan(angle) + 1
DERIVATE
        (bool) pushOut = intention > 0 AND obstructOut
        (bool) pushIn = intention < 0 AND obstructIn
PROTOCOL
        intention > 0 AND !obstructOut -> pos = |pos| + 1
        intention < 0 AND !obstructIn -> pos = |pos| - 1
        true -> intention = 1
        true -> intention = 0
        true -> intention = -1
}