Anonymous Unions

Members of an anonymous union look like members of the enclosing class.

Without using anonymous unions in classes, you need to use the union name when referencing a union member. For example: myObject.myUnion.myMember instead of myObject.myMember.

Reference: C++ Templates by David Vandevoorde and Nicolai M. Josuttis. Addison-Wesley, 2003, p. 143.