// Warning: Microsoft Visual C++ Compiler cannot compile methods of inner
// nested classes inside a template defined outside of template body! For inner
// nested classes inside a template, you must define functions inside the class.
// Such functions automatically become inline functions. This error is
// generated for code allowed by the standard of C++ language, however, not
// yet supported by Microsoft Visual C++. So, if you get an error, just move
// the method into a nested class of a template.