程序代码：

 namespace string
  {
    template<typename _Base, typename _Result>
    std::basic_string<_Result> convert(const std::basic_string<_Base> &base, unsigned int codepage = 1252)
    { }

    template<>
    std::basic_string<char> convert(const std::basic_string<char> &base, unsigned int codepage)
    { return base; }
}