Board index » cppbuilder » case insensitive wchars

2005-08-02 03:52:01 AM
cppbuilder26
I'm writing a platform-independant function that compares two wchar_t
strings together, with and without case sensitivity.
But, I've run into a problem with trying to make the two strings lowercase
so that I can compare them.
How can I convert wchar_t strings to lowercase ?
I'm using std::wstring to handle the strings.
Jonathan
 

"Jonathan Benedicto" < XXXX@XXXXX.COM >writes:
would require the software to understand the text.
 

"Thomas Maeder [TeamB]" < XXXX@XXXXX.COM >wrote in message
the lowercase conversion on english characters ?
I'm very sorry for being so ignorant about this. I'm just learning about
Unicode.
Jonathan
 

{smallsort}

Jonathan Benedicto < XXXX@XXXXX.COM >wrote:
Win32 API lstrcmpi() can perform a comparison with no case sensitivity.
But as the documentation said:
For some locales, the lstrcmpi function may be insufficient. If this
occurs, use CompareString to ensure proper comparison.
--
JF Jolin
 

"JF Jolin" < XXXX@XXXXX.COM >wrote in message
Jonathan
 

"Jonathan Benedicto" < XXXX@XXXXX.COM >writes:
know.
There is no such thing as "english characters" (well, the term
"character" is overloaded, but you know what I mean :-) ). English
texts are commonly written in the Latin alphabet. Which is one of the
few alphabets used on this planet that distinguish between upppercase
and lowercase characters (the other one I know is the cyrillic
alphabet).
To correctly perform the conversion to lowercase in German and French
text (both typically written in the Latin alphabet), your software
needs to understand the text. I'd assume that other languages would
apply as well, but I can't tell for sure.
So if you *know* that a certain text is in English, it may be safe to
do the conversion to lowercase character per character, as typical
functions do it.
least mean that you how the text is encoded.
 

JF Jolin < XXXX@XXXXX.COM >writes:
E.g. to tell if MASSE and Maße should compare equal, understanding of
the text is required.
 

"Thomas Maeder [TeamB]" < XXXX@XXXXX.COM >wrote in message
think that I'll ever be able to determine what data is placed into the
class.
I think that maybe I should use that open-source ICU library instead of
trying to handle the wchar myself.
Jonathan
 

"Thomas Maeder [TeamB]" < XXXX@XXXXX.COM >wrote in message
allowed to drop the accent or not in the capitalized format.
We're currently working with this same concept and it's quite complex.
The best we've found so far is to find a cross platform library (QString
in our case) that handles Unicode and do the comparisons with these objects.
But even this isn't perfect due to examples like the above.
I have no idea how you would do this with anything from std c++.
Dealing with std::string or wstring doesn't really work. You basically
have to use something like UTF8 as an intermediate and then you
have problems with normalization and such. As well as the fact that
there can be more than one valid UTF8 encoding for the same
unicode character. Then on top of that, not everyone uses UTF8.
You have to deal with UTF16 and UCS2 for example.
 

"Duane Hebert" < XXXX@XXXXX.COM >wrote in message
case, that would mean making the function not support case-insensitive
comparison, or as I have it now, make the case sensitive option use the
tolower function.
Jonathan
 

"Jonathan Benedicto" < XXXX@XXXXX.COM >writes:
that price is very hard to beat :-)
But this library deals with Unicode, not necessarily with wchar_t
strings, if I understand
www-306.ibm.com/software/globalization/icu/index.jsp correctly.
I have the feeling that you are seeing an equivalence between wchar_t
and Unicode that isn't there. wchar_t objects can be used to represent
Unicode characters; but they can be used for other things as
well. OTOH, Unicode characters can be represented by wchar_t objects,
but there are other representations.
On platforms where sizeof(wchar_t)==2, a representation different from
wchar_t is likely to be more useful since 21 bits are required to
represent all Unicode code points; if the set of Unicode characters to
be represented doesn't exclude these characters (I think they are used
in Thailand), you're probably better of with a 32bit character type.
 

Thomas Maeder [TeamB] < XXXX@XXXXX.COM >wrote:
Do we start a debate over equivalence and comparison ?
What about synonym ?
Fruit and color orange are two different realities.
This is endless...
--
JF Jolin
 

"Thomas Maeder [TeamB]" < XXXX@XXXXX.COM >wrote in message
char_traits<int>, allocator<int>>might be better because it would provide
32-bit character sizes ?
Jonathan
 

Duane Hebert < XXXX@XXXXX.COM >wrote:
'std::basic_string<>'. Basically, we determine
'wchar_t's size at compile-time and decide
what to use for character types.
On Windows, the main internal representation
is UCS-2 (i.e. those Unicode chars that need
only 16bit) because that's what Windows does.
On OS X the same type (but with a 'wchar_t'
of 32bit) carries UTF-32 (which I think is
safe so far, as there aren't any UTF-32 chars
needing more than 32bit), because it's (AFAIK)
what OS X uses internally.
Schobi
--
XXXX@XXXXX.COM is never read
I'm Schobi at suespammers dot org
"Coming back to where you started is not the same as never leaving"
Terry Pratchett
 

"Hendrik Schober" < XXXX@XXXXX.COM >wrote in message
unc to different boxes. So far, it's mostly linux and
windows. We've been using std::string
with UTF8 for the config stuff. The classes that are
non-gui deal with them straight. The gui classes that
allow user I/O with some of this data use QString which
has to/from utf8 functions.
So far it's been working well
but the OP asked for cross platform standard way of
doing things. Your answer may be more suitable
to him.