C++Talk.NET

Ralf Goertz · Guest

Hi,

since my previous post
<455440ad$0$30326$9b4e6d93 (AT) newsspool1 (DOT) arcor-online.net> is still
unanswered I'd like to rephrase my question. In order to read/write a
wstring in UTF-8 encoding it is *not* sufficient to imbue the stream
with a locale like "de_DE.UTF-8". Doing so only takes care of facets of
decimal numbers and the like. Rather, one has to call
locale::global("de_DE.UTF-8"). Is this behaviour conforming to the
standard? And if so why? I mean why wouldn't wcin.imbue("de_DE.UTF-8")
make wcin accept UTF-8 multibyte characters while still allowing 5,7 to
be parsed as 5.7?

file wcintest.cc:
-------------
#include <iostream>
#include <string>
#include <locale>
using namespace std;

float f;
wstring euro;

int main(){
locale l("de_DE.UTF-8");
wcin.imbue(l);
locale::global(l); // (*)
wcin>>f>>euro;
wcout.imbue(locale("en_US.UTF-8"));
wcout<<f<<L" "<<euro<<endl;
}
-------------

Calling

$ echo "5,70 â‚¬" |./wcintest

in a UTF-8 environment gives

5.70 â‚¬

but only if the line marked (*) is present. Otherwise you only get

5.70

It seems as if the encoding part of the locale is ignored by the imbue
calls but I don't see why this should be the case.

I use g++ (GCC) 4.1.0 under linux (i386).

Ralf

ondra.holub · Guest

Currently I do not have linux here (at work) so I am only guessing. Did
you try to change locale of output to German locale?

wcout.imbue(l);

Maybe the euro sign is not accepted by US locale.

ondra.holub · Guest

I think that tolower function is not designed for C++. There should be
used facets instead, but the code looks a bit complicated:

#include <iostream>
#include <locale>

int main()
{
std::locale loc("german");
char s[] = "äÖü";

std::use_facet< std::ctype<char> >(loc).tolower(s, s + sizeof(s));
std::cout << s << std::endl;

std::use_facet< std::ctype<char> >(loc).toupper(s, s + sizeof(s));
std::cout << s << std::endl;

return 0;
}

Ralf Goertz · Guest

ondra.holub wrote:

Ralf Goertz · Guest

I wrote: