@Override
    public int eval(Critter c) {
        // TODO implement me!
        // returns the boolean value of this expression for Critter c
    	int value;
    	if (op.toString().equals("+"))
    		value = left.eval(c) + right.eval(c);
    	else if (op.toString().equals("-"))
    		value = left.eval(c) - right.eval(c);
    	else if (op.toString().equals("*"))
    		value = left.eval(c) * right.eval(c);
    	else if (op.toString().equals("/")){
    		int r = right.eval(c);
    		if(r == 0) return 0;
    		value = left.eval(c) / r;
    	}
    	else if (op.toString().equals("mod")){
    		int r = right.eval(c);
    		if(r == 0) return 0;
    		value = left.eval(c) % right.eval(c);
    	}
    	else {
    		System.out.println("Error in Arithmetic eval");
    		value = 0;
    	}
    	return value;
    }