Adding types to the std namespace

Question

Is it acceptable to add types to the std namespace. For example, I want a TCHAR-friendly string, so is the following acceptable?

#include 

        

Answer 1

[C++11: 17.6.4.2.1/1]: The behavior of a C++ program is undefined if it adds declarations or definitions to namespace std or to a namespace within namespace std unless otherwise specified. A program may add a template specialization for any standard library template to namespace std only if the declaration depends on a user-defined type and the specialization meets the standard library requirements for the original template and is not explicitly prohibited.