Re: locale in c++

Hi,

I am confronted with an unexpected behavior of std::locale. Consider
the following small example:

#include <locale>
#include <sstream>
#include <isotream>
#include <locale.h>

int main ( int argc, const char** argv ) {
    std::locale* loc;
    try {
        loc = new std::locale ( argv[1] );
    }
    catch ( std::runtime_error e ) {
        std::cerr << e.what ( ) << std::endl;
        loc = new std::locale ( );
    }
    //setlocale ( LC_ALL, loc->name ().c_str () );
    std::wistringstream wsin ( L"??sop" );
    wsin.imbue ( *loc );
    std::wcout.imbue ( *loc );
    wint_t act;
    while ( wsin.good () ) {
        act = wsin.get ();
        std::wcout << std::isalpha<wchar_t> ( (wchar_t)act, *loc ) <<
L" " << (wchar_t)act << std::endl;
    }
    return 0;
}

Running as "./locale_test en_US.UTF-8" gives me
1 ?
1 s
1 o
1 p
0
If I uncomment the 'setlocal' line output is
1 ??
1 s
1 o
1 p
0

But why? I understood that 'imbueing' std::cout should do the trick of
printing wide characters. If anybody has a clue, please tell me.