Q: Convert std::string to std::wstring using std::ctype widen()

Hi All,

I've done a little homework (I've read responses to similar from P.J.
Plauger and Dietmar Kuehl), and wanted to verify with the Group. Over
in comp.lang.c++, I'm getting a lot of boot Microsoft answers (which
does not help me). Below is what I am performing (Stroustrup's Appendix
D recommendations won't compile in Microsoft VC++ 6.0).

My question is in reference to MultiByte Character Sets. Will this code
perform as expected? I understand every problem has a simple and
elegant solution that is wrong.

I generally use US English or Unicode, so I don't encounter a lot of
issues others may see (a multibyte character using std::string). I have
verified it works with a Hello World sample.

Before I get flamed for not using std::codecvt, Stroustrup states
(D.4.6 Character Code Conversion, p 925):
The codecvt facet provides conversion between different character sets
when a character is moved between a stream buffer and external
storage...

Jeff
Jeffrey Walton

    std::string s = "Hello World";
    std::ctype<wchar_t> ct;
    std::wstring ws;

    for( std::string::const_iterator it = s.begin();
                                     it != s.end(); it++ )
    {
        ws += ct.widen( *it );
    }

    // Stroustrup again (Section D.4.5, p. 923):
    // A call widen(c) transforms the character c into its
corresponding Ch value.
    // If Ch's character set provides several characters
corresponding to c, the
    // standard specifies that "the implest reasonable
transformation" be used.

    // http://www.research.att.com/~bs/3rd_loc.pdf
    // by Bjourne himself...
    // page 28 of the above reference
    // or
    // The C++ Programming Language, Special Edition
    // Section D.4.2.2, p 895 (Full Manual)
    //
    // const std::locale& loc = s.getloc();
    // wchar_t w = std::use_facet< std::ctype<char> >
    // (loc).widen(c);
    // does not compile in Microsft's VC++ 6.0 environment...
    // getloc() is not a member of std::basic_string< ... > ...
    //
    // wchar_t wc = std::use_facet< std::ctype<wchar_t> >
    // (out.getloc()).widen(*it);
    // does not compile in Microsft's VC++ 6.0 environment...

    //
    // Dietmar Kuehl code
    // does not compile in Microsft's VC++ 6.0 environment...
    //
    // std::wstring to_wide_string(std::string const& source) {
    // typedef std::ctype<wchar_t> CT;
    // std::wstring rc;
    // rc.resize(source.size());
    // CT const& ct = std::use_facet<CT>(std::locale());
    // ct.widen(source.data(), source.data() +
    // source.size(), rc.data());
    // return rc;