Assign a new random direction to data member that is different from the current in c++

Question

class Child:public Parent{
public:
    enum Direction { Left, Right, Up, Down };
    Direction direction;
    void Update();            
private:
    int x,y;
    void ChangeDirection();
    void Draw();

};

I need the Update() function which invokes ChangeDirection() and Draw() to increment and decrements the x y values upon current direction which i have done. My problem is that y or x cannot be (-)value.

And also ChangeDirection() should assign a random direction to direction data and again this direction must be different to current direction. I was able to cout random directions within the same ChangeDirection() function this way

Direction direction = static_cast<Direction>(rand() % 4);
cout << direction;

but again sometime it prints the same direction. Now what i want is, the random assignment to direction should occur in ChangeDirection() member function not allowing the current value again but it should display the results through the void Draw(); member function which increments or decrements the x y values without letting it to be (-)value (should be clamped to 0). this is what i have done for that.

if ( direction == 0 ){
    cout << "Right";
    x++;
}
else if (direction == 1 ){
    cout << "Down";
    y++;
}
else if (direction == 2 ){
    cout << "Up";
    y--;
}
else if (direction == 3 ){
    cout << "Left";
    x--;
}
Draw();

But it is giving (-)values. how do I step forward ..

Answer 1

Since you are assigning a random direction, it makes sense that the direction which is assigned sometimes is equal to the previous direction. Try something like:

Direction direction = static_cast<Direction>((currentDirection + 1 + (rand() % 3) ) % 4);

to ensure that you get a new direction

Edit: To answer the other part of your question, you must check the value of x and y prior to incrementing or decrementing to ensure that they are within the bounds of whatever you are currently using. Here is an example of what I am talking about:

 if(x > 0){
   x--;
 } else {
 //do something else
 }