[shandrin]

The problem is that you're declaring pointers to DigitalInputs, and then trying to initialize them in the initialization list. You either need to declare them as actual DigitalInput objects (no *) or instead of left(1), middle(2), right(3), you need to have inside the constructor (where you note "error here"):
left = new DigitalInput(1);
middle = new DigitalInput(2);
right = new DigitalInput(3);

Hope that helps!