C++Talk.NET C++ language newsgroups   Archives   FAQ   Search   Memberlist   Usergroups   Register   Profile   Log in to check your private messages   Log in  wostream &operator <<(wostream &, string const &)?          C++Talk.NET Forum Index -> C++ language, library and standards View previous topic :: View next topic   Author Message Køi¹tof ®elechovski Guest Posted: Tue Aug 08, 2006 5:03 pm    Post subject: wostream &operator <<(wostream &, string const &)? I am trying to go Unicode with my code base. I noticed that in most cases I can safely replace cout with wcout since all standard types behave correctly. However, all but one. The offender is std::string. I cannot send it to std::wcout. WHY? If std::string is a replacement for char const [] and I can send char const [] to std::wcout, why cannot I do the same with a std::string? I thought about a workaround: it is easy to implement. But I am not sure I am allowed to do this, which is my question: std::wostream &operator <<(std::wostream &, std::string const &); I feel such an operator should be in the standard and my definition is a patch. The standard forbids patching the standard library, doesn't it? And also I would like to know how to get rid of the following annoying problem: the code that sends wchar_t const [] to std::cout compiles and prints the address of the buffer which is obviously meaningless. Since it is hard to find all such places in the code, I would prefer if the compiler could report them to me. Is it possible to set up the environment so as to catch such dangerous places? Chris --- [ comp.std.c++ is moderated. To submit articles, try just posting with ] [ your news-reader. If that fails, use mailto:std-c++@ncar.ucar.edu ] [ --- Please see the FAQ before posting. --- ] [ FAQ: http://www.comeaucomputing.com/csc/faq.html ] Back to top AllanW Guest Posted: Tue Aug 08, 2006 8:56 pm    Post subject: Re: wostream &operator <<(wostream &, string const &)? "Køi¹tof ®elechovski" wrote: Quote: I am trying to go Unicode with my code base. I noticed that in most cases I can safely replace cout with wcout since all standard types behave correctly. However, all but one. The offender is std::string. I cannot send it to std::wcout. WHY? If std::string is a replacement for char const [] and I can send char const [] to std::wcout, why cannot I do the same with a std::string? Have you tried the same with a std::wstring? --- [ comp.std.c++ is moderated. To submit articles, try just posting with ] [ your news-reader. If that fails, use mailto:std-c++@ncar.ucar.edu ] [ --- Please see the FAQ before posting. --- ] [ FAQ: http://www.comeaucomputing.com/csc/faq.html ] Back to top Kristof Zelechovski Guest Posted: Wed Aug 09, 2006 4:32 pm    Post subject: Re: wostream &operator <<(wostream &, string const &)? Uzytkownik "AllanW" <allan_w@my-dejanews.com> napisal w wiadomosci news:1155062150.001381.325180 (AT) h48g2000cwc (DOT) googlegroups.com... Quote: "Køi¹tof ®elechovski" wrote: I am trying to go Unicode with my code base. I noticed that in most cases I can safely replace cout with wcout since all standard types behave correctly. However, all but one. The offender is std::string. I cannot send it to std::wcout. WHY? If std::string is a replacement for char const [] and I can send char const [] to std::wcout, why cannot I do the same with a std::string? Have you tried the same with a std::wstring? Yes, I have. But what does it buy me? Nothing. Because std::wcout and std::string is what I have. Chris --- [ comp.std.c++ is moderated. To submit articles, try just posting with ] [ your news-reader. If that fails, use mailto:std-c++@ncar.ucar.edu ] [ --- Please see the FAQ before posting. --- ] [ FAQ: http://www.comeaucomputing.com/csc/faq.html ] Back to top Guest Posted: Wed Aug 09, 2006 4:40 pm    Post subject: Re: wostream &operator <<(wostream &, string const &)? "Kristof Zelechovski" wrote: Quote: Uzytkownik "AllanW" <allan_w@my-dejanews.com> napisal w wiadomosci news:1155062150.001381.325180 (AT) h48g2000cwc (DOT) googlegroups.com... "Køi¹tof ®elechovski" wrote: I am trying to go Unicode with my code base. I noticed that in most cases I can safely replace cout with wcout since all standard types behave correctly. However, all but one. The offender is std::string. I cannot send it to std::wcout. WHY? If std::string is a replacement for char const [] and I can send char const [] to std::wcout, why cannot I do the same with a std::string? Have you tried the same with a std::wstring? Yes, I have. But what does it buy me? Nothing. Because std::wcout and std::string is what I have. Well, as long as you have std::string rather than std::wstring, you haven't converted completely to wide characters. And as long as you have a mixture of narrow and wide character types, you're going to have to deal periodically with converting between them. --- [ comp.std.c++ is moderated. To submit articles, try just posting with ] [ your news-reader. If that fails, use mailto:std-c++@ncar.ucar.edu ] [ --- Please see the FAQ before posting. --- ] [ FAQ: http://www.comeaucomputing.com/csc/faq.html ] Back to top Kristof Zelechovski Guest Posted: Thu Aug 10, 2006 3:46 pm    Post subject: Re: wostream &operator <<(wostream &, string const &)? Uzytkownik <kuyper (AT) wizard (DOT) net> napisal w wiadomosci news:1155135995.608597.116130 (AT) i42g2000cwa (DOT) googlegroups.com... Quote: "Kristof Zelechovski" wrote: Uzytkownik "AllanW" <allan_w@my-dejanews.com> napisal w wiadomosci news:1155062150.001381.325180 (AT) h48g2000cwc (DOT) googlegroups.com... "Køi¹tof ®elechovski" wrote: I am trying to go Unicode with my code base. I noticed that in most cases I can safely replace cout with wcout since all standard types behave correctly. However, all but one. The offender is std::string. I cannot send it to std::wcout. WHY? If std::string is a replacement for char const [] and I can send char const [] to std::wcout, why cannot I do the same with a std::string? Have you tried the same with a std::wstring? Yes, I have. But what does it buy me? Nothing. Because std::wcout and std::string is what I have. Well, as long as you have std::string rather than std::wstring, you haven't converted completely to wide characters. And as long as you have a mixture of narrow and wide character types, you're going to have to deal periodically with converting between them. In order to convert completely to wide characters, I would have to use std::cout for an ANSI build and std::wcout for an Unicode build, right? And how do you achieve that? By replacing all references to std::cout with a function call? use_cout<_TCHAR>() << std::endl? It does not look particularly well. I used std::wcout for both Unicode and ANSI builds but I stumbled on the std::string problem. Therefore my question: I can std::wcout << "", why cannot I std::wcout << std::string("")? It seems something is missing here. Chris --- [ comp.std.c++ is moderated. To submit articles, try just posting with ] [ your news-reader. If that fails, use mailto:std-c++@ncar.ucar.edu ] [ --- Please see the FAQ before posting. --- ] [ FAQ: http://www.comeaucomputing.com/csc/faq.html ] Back to top peter koch Guest Posted: Fri Aug 11, 2006 7:06 pm    Post subject: Re: wostream &operator <<(wostream &, string const &)? kuyper (AT) wizard (DOT) net wrote: Quote: "Kristof Zelechovski" wrote: Uzytkownik "AllanW" <allan_w@my-dejanews.com> napisal w wiadomosci news:1155062150.001381.325180 (AT) h48g2000cwc (DOT) googlegroups.com... "Køi¹tof ®elechovski" wrote: I am trying to go Unicode with my code base. I noticed that in most cases I can safely replace cout with wcout since all standard types behave correctly. However, all but one. The offender is std::string. I cannot send it to std::wcout. WHY? If std::string is a replacement for char const [] and I can send char const [] to std::wcout, why cannot I do the same with a std::string? Have you tried the same with a std::wstring? Yes, I have. But what does it buy me? Nothing. Because std::wcout and std::string is what I have. Well, as long as you have std::string rather than std::wstring, you haven't converted completely to wide characters. And as long as you have a mixture of narrow and wide character types, you're going to have to deal periodically with converting between them. This is not necesarily so. You can imagine applications that use a mix of char and wchar_t strings (the application I currently work on has this). Some parts of the system has to access external data that is keyed on 8-bit characters (e.g. resource files, databases and so on). Even if the application per se is unicode, this will not be the case for the external data - ever. So how can I present the data if I can't strem it to a wide output stream? I believe it is a reasonable expectation that the conversion is handled automatically. /Peter --- [ comp.std.c++ is moderated. To submit articles, try just posting with ] [ your news-reader. If that fails, use mailto:std-c++@ncar.ucar.edu ] [ --- Please see the FAQ before posting. --- ] [ FAQ: http://www.comeaucomputing.com/csc/faq.html ] Back to top SuperKoko Guest Posted: Tue Aug 15, 2006 3:01 pm    Post subject: Re: wostream &operator <<(wostream &, string const &)? Kristof Zelechovski wrote: Quote: In order to convert completely to wide characters, I would have to use std::cout for an ANSI build and std::wcout for an Unicode build, right? And how do you achieve that? By replacing all references to std::cout with a function call? use_cout<_TCHAR>() << std::endl? It does not look particularly well. I used std::wcout for both Unicode and ANSI builds but I stumbled on the std::string problem. Therefore my question: I can std::wcout << "", why cannot I std::wcout << std::string("")? It seems something is missing here. Obvious solution : At a namespace scope in your program: #ifdef UNICODE /* or something like that*/ std::ostream& tcout=std::wcout; #else std::ostream& tcout=std::wcout; #endif Or perhaps std::ostream& tcout=(sizeof(_TCHAR)==sizeof(char))?std::cout : std::wcout; Køi¹tof ®elechovski wrote: Quote: I thought about a workaround: it is easy to implement. But I am not sure I am allowed to do this, which is my question: std::wostream &operator <<(std::wostream &, std::string const &); Adding overloads to namespace std is not allowed (and it might potentially be a name clash problem if the standard adds this exact overload in C++0x) However, if your above function is not declared in namespace std (declared in the global namespace), thanks to koenig lookup, it should work as expected. So, basically, I think that your workaround is legal. --- [ comp.std.c++ is moderated. To submit articles, try just posting with ] [ your news-reader. If that fails, use mailto:std-c++@ncar.ucar.edu ] [ --- Please see the FAQ before posting. --- ] [ FAQ: http://www.comeaucomputing.com/csc/faq.html ] Back to top James Kanze Guest Posted: Wed Aug 16, 2006 5:26 pm    Post subject: Re: wostream &operator <<(wostream &, string const &)? Kristof Zelechovski wrote: Quote: Uzytkownik <kuyper (AT) wizard (DOT) net> napisal w wiadomosci news:1155135995.608597.116130 (AT) i42g2000cwa (DOT) googlegroups.com... "Kristof Zelechovski" wrote: Uzytkownik "AllanW" <allan_w@my-dejanews.com> napisal w wiadomosci news:1155062150.001381.325180 (AT) h48g2000cwc (DOT) googlegroups.com... "Køi¹tof ®elechovski" wrote: I am trying to go Unicode with my code base. I noticed that in most cases I can safely replace cout with wcout since all standard types behave correctly. However, all but one. The offender is std::string. I cannot send it to std::wcout. WHY? If std::string is a replacement for char const [] and I can send char const [] to std::wcout, why cannot I do the same with a std::string? Have you tried the same with a std::wstring? Yes, I have. But what does it buy me? Nothing. Because std::wcout and std::string is what I have. Well, as long as you have std::string rather than std::wstring, you haven't converted completely to wide characters. And as long as you have a mixture of narrow and wide character types, you're going to have to deal periodically with converting between them. In order to convert completely to wide characters, I would have to use std::cout for an ANSI build and std::wcout for an Unicode build, right? First, the standard doesn't say anything about Unicode. As far as the standard is concerned, wchar_t can have the same type and encoding as char. Typically, it will be larger, however, at least on general purpose machines, but that still doesn't guarantee Unicode. And of course, which representation of Unicode: Unicode defines three encoding forms: UTF-8, UTF-16 and UTF-32---UTF-16 and UTF-32 exist in big endian and little endian formats, when used on 8 bit media. If you are using UTF-16 (Windows, AIX) or UTF-32 (most other systems) internally, you need to use wchar_t (supposing that your implementation supports one of these with wchar_t). Everywhere, which means std::wstring, L"..." for string literals, and L'...' for character constants, along with the wide character versions of the iostream classes. If you are using UTF-8, on the other hand, you will continue using the char versions (i.e. std::string, std::cout, etc.), but you'd best be prepared for some extra work if you do any character handling. Quote: And how do you achieve that? By replacing all references to std::cout with a function call? use_cout<_TCHAR>() std::endl? It does not look particularly well. Wide characters and narrow characters are two different beasts. For that matter, UTF-16 and UTF-32 are two different beasts. If you're doing anything complicated, you'll have to maintain two different versions. Otherwise, a judicious use of typedefs and maybe a few macros can help: // header ansi/characters.hh namespace characters { typedef std::string string ; typedef std::istream istream ; // ... std::ostream& cout = std::cout ; // ... } and // header unicode/characters.hh namespace characters { typedef std::wstring string ; typedef std::wistream istream ; // ... std::wostream& cout = std::wcout ; // ... } Include one or the other using -I (or /I, depending on your compiler). -- James Kanze kanze.james (AT) neuf (DOT) fr Conseils en informatique orientée objet/ Beratung in objektorientierter Datenverarbeitung 9 place Sémard, 78210 St.-Cyr-l'École, France +33 (0)1 30 23 00 34 --- [ comp.std.c++ is moderated. To submit articles, try just posting with ] [ your news-reader. If that fails, use mailto:std-c++@ncar.ucar.edu ] [ --- Please see the FAQ before posting. --- ] [ FAQ: http://www.comeaucomputing.com/csc/faq.html ] Back to top Seungbeom Kim Guest Posted: Wed Aug 16, 2006 9:27 pm    Post subject: Re: wostream &operator <<(wostream &, string const &)? SuperKoko wrote: Quote: Obvious solution : At a namespace scope in your program: #ifdef UNICODE /* or something like that*/ std::ostream& tcout=std::wcout; #else std::ostream& tcout=std::wcout; #endif Or perhaps std::ostream& tcout=(sizeof(_TCHAR)==sizeof(char))?std::cout : std::wcout; std::wcout is of type std::wostream, not std::ostream, therefore it cannot bind to a reference to std::ostream. #ifdef UNICODE std::wostream& tcout = std::wcout; #else std::ostream& tcout = std::cout; #endif is possibly acceptable. -- Seungbeom Kim --- [ comp.std.c++ is moderated. To submit articles, try just posting with ] [ your news-reader. If that fails, use mailto:std-c++@ncar.ucar.edu ] [ --- Please see the FAQ before posting. --- ] [ FAQ: http://www.comeaucomputing.com/csc/faq.html ] Back to top Kristof Zelechovski Guest Posted: Wed Aug 16, 2006 9:27 pm    Post subject: Re: wostream &operator <<(wostream &, string const &)? Uzytkownik "SuperKoko" <tabkannaz (AT) yahoo (DOT) fr> napisal w wiadomosci news:1155368731.463685.267490 (AT) 75g2000cwc (DOT) googlegroups.com... Quote: Or perhaps std::ostream& tcout=(sizeof(_TCHAR)==sizeof(char))?std::cout : std::wcout; Ill-formed: cannot cast from std::wostream to std::ostream. Chris --- [ comp.std.c++ is moderated. To submit articles, try just posting with ] [ your news-reader. If that fails, use mailto:std-c++@ncar.ucar.edu ] [ --- Please see the FAQ before posting. --- ] [ FAQ: http://www.comeaucomputing.com/csc/faq.html ] Back to top Kristof Zelechovski Guest Posted: Fri Aug 18, 2006 9:13 pm    Post subject: Re: wostream &operator <<(wostream &, string const &)? Quote: Wide characters and narrow characters are two different beasts. For that matter, UTF-16 and UTF-32 are two different beasts. If you're doing anything complicated, you'll have to maintain two different versions. Otherwise, a judicious use of typedefs and maybe a few macros can help: // header ansi/characters.hh namespace characters { typedef std::string string ; typedef std::istream istream ; // ... std::ostream& cout = std::cout ; // ... } and // header unicode/characters.hh namespace characters { typedef std::wstring string ; typedef std::wistream istream ; // ... std::wostream& cout = std::wcout ; // ... } Include one or the other using -I (or /I, depending on your compiler). I still do not see the need for such a complication. I can send primitive types to both specializations, with the exception of wchar_t [], which makes std::wcout more universal and preferable. But then, all of a sudden, the std::string says 'No way'. If std::string is meant to be a replacement for char [], it should behave the same way with respect to std::wcout. Chris --- [ comp.std.c++ is moderated. To submit articles, try just posting with ] [ your news-reader. If that fails, use mailto:std-c++@ncar.ucar.edu ] [ --- Please see the FAQ before posting. --- ] [ FAQ: http://www.comeaucomputing.com/csc/faq.html ] Back to top kanze Guest Posted: Mon Aug 21, 2006 3:51 pm    Post subject: Re: wostream &operator <<(wostream &, string const &)? "Kristof Zelechovski" wrote: Quote: Wide characters and narrow characters are two different beasts. For that matter, UTF-16 and UTF-32 are two different beasts. If you're doing anything complicated, you'll have to maintain two different versions. Otherwise, a judicious use of typedefs and maybe a few macros can help: // header ansi/characters.hh namespace characters { typedef std::string string ; typedef std::istream istream ; // ... std::ostream& cout = std::cout ; // ... } and // header unicode/characters.hh namespace characters { typedef std::wstring string ; typedef std::wistream istream ; // ... std::wostream& cout = std::wcout ; // ... } Include one or the other using -I (or /I, depending on your compiler). I still do not see the need for such a complication. I can send primitive types to both specializations, with the exception of wchar_t [], which makes std::wcout more universal and preferable. Whether you chose wcout or cout should depend more on the types of data you wish to handle internally. It's more of an anomalie that you can send a char* (pointing to a char[]) to a wcout. One normally wouldn't expect it to work at all, but doubtlessly, there are issues concerning interfaces with legacy code and/or the C library (e.g. the return value of strerror). Quote: But then, all of a sudden, the std::string says 'No way'. If std::string is meant to be a replacement for char [], it should behave the same way with respect to std::wcout. It's meant to be a replacement for char[] in new code. It certainly doesn't interface directly to legacy code, the C library, or e.g. Posix interfaces. I don't think that you're meant to output a char[] to a wcout in new code; logically, wcout wouldn't even support it, but as I said, there is the problem of libraries using a C ABI. Obviously, said problem doesn't concern std::string, so the hack isn't present for std::string. -- James Kanze GABI Software Conseils en informatique orientée objet/ Beratung in objektorientierter Datenverarbeitung 9 place Sémard, 78210 St.-Cyr-l'École, France, +33 (0)1 30 23 00 34 --- [ comp.std.c++ is moderated. To submit articles, try just posting with ] [ your news-reader. 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