Re: isspace

From:
Paavo Helde <myfirstname@osa.pri.ee>
Newsgroups:
comp.lang.c++
Date:
Sun, 31 Jan 2010 07:17:16 -0600
Message-ID:
<Xns9D119B9AB9890paavo256@216.196.109.131>
gervaz <gervaz@gmail.com> wrote in
news:a5a4ece2-5b9d-4846-a818-9de61c130654@r24g2000yqd.googlegroups.com:

On Jan 31, 10:39?am, Paavo Helde <myfirstn...@osa.pri.ee> wrote:

Paavo Helde <myfirstn...@osa.pri.ee> wrote
innews:Xns9D116950C4paavo256@2

16.196.109.131:

gervaz <ger...@gmail.com> wrote in news:f9eec1c9-5570-461a-bdec-
6dec26dab...@o28g2000yqh.googlegroups.com:

On Jan 30, 1:15?pm, James Kanze <james.ka...@gmail.com> wrote:

On Jan 30, 12:05 pm, r...@zedat.fu-berlin.de (Stefan Ram) wrote:

James Kanze <james.ka...@gmail.com> writes:

There are no standard names for locales

? AFAIK, C90 defines a locale by the name of "C",
? which should also be visible from C++.


And Posix defines "POSIX". ?Neither of which are really useful
for anything.

--
James Kanze


Ok, so I think that I will open my file specifying to use UTF-8
encoding, but how can I do it in C++?


You can open it as a narrow stream and read in as binary UTF-8, or
(maybe) you can open it as a wide stream and get an automatic
translation from UTF-8 to wchar_t. The following example assumes
that you have a file test1.utf containing valid UTF-8 text. It
reads the file in as a wide stream and prints out the numeric
values of all wchar_t characters.

#include <iostream>
#include <fstream>
#include <locale>
#include <string>

int main() {
? ? std::wifstream is;
? ? const std::locale filelocale("en_US.UTF8");
? ? is.imbue(filelocale);
? ? is.open("test1.utf8");

? ? std::wstring s;
? ? while(std::getline(is, s)) {
? ? ? ? for (std::wstring::size_type j=0; j<s.length(); ++j)

{

? ? ? ? ? ? std::cout << s[j] << " ";
? ? ? ? }
? ? ? ? std::cout << "\n";
? ? }
}

(Tested on Linux with a recent gcc, I am not too sure if this works
on Windows. First, wchar_t in MSVC is too narrow for real Unicode,
at best one might get UTF-16 as a result.)


For curiosity, I tested this also on Windows with MSVC9, and as
expected it did not work, the locale construction immediately threw
an exception (bad locale name). Neither did any alterations work
("english.UTF8", ".UTF8", ".utf-8", ".65001").

Thus, if one wants any portability it seems the best approach
currently is still to read in binary UTF-8 and perform any needed
conversions by hand.

Paavo


Under Windows, you have to use const std::locale filelocale
("English_Australia.1252") according to
http://docs.moodle.org/en/Table_of_locales, I've tested it in VC++08
and it works. Any suggestion in how to handle the dualism?


Did you actually test the results? It seems this is reading UTF-8 in
unaltered, so there is no point to use a wide stream in the first place.

Paavo

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