I would like to convert between std::wstring and std::string using lexical_cast and finally discovered in an old posting that you must manually provide template specializations for these types as below. My question is why these aren't provided in lexical_cast.hpp already? template<> inline std::wstring boost::lexical_cast(std::string source) { std::wstring result(source.size(), wchar_t(0)); typedef std::ctype<wchar_t> ctype_t; const ctype_t& ct = std::use_facet<ctype_t>(std::locale()); ct.widen(source.data(), source.data() + source.size(), &(*result.begin())); return result; } template<> inline std::string boost::lexical_cast(std::wstring source) { std::string result(source.size(), char(0)); typedef std::ctype<wchar_t> ctype_t; const ctype_t& ct = std::use_facet<ctype_t>(std::locale()); ct.narrow(source.data(), source.data() + source.size(), '\u00B6', &(*result.begin())); return result; }