private DrawCanvas drawVar(String string, int i) {
        DrawCanvas drawCanvas = null;
        switch (string.charAt(i)) {
            case 'F':
                drawCanvas = drawStep();
                break;
            case 'b':
                moveStep();
                break;
            case '+':
                rotateRight();
                break;
            case '-':
                rotateLeft();
                break;
            case '[':
                pushState();
                break;
            case ']':
                popState();
                break;
            default:
                break;
        }
        return drawCanvas;
    }