::                      Scope Resolution Operator

 class name::identifier

    The scope resolution operator is unique to C++. It lets you refer
    to a global identifier even if that identifier has been hidden by
    a local redeclaration. For example, you can define a member
    function (my_func()) of a class like this:

                class my_class
                {
                    int my_var;
                public:
                    int my_func();
                };


                int my_class::my_func()
                {
                    return 0;
                };