_T( in code...

[edit] It is, in fact, a macro.
#define _T(x) __T(x)
#define __T(x) L ## x

I think it does something related to strings.

[edited by - jflanglois on May 14, 2004 9:35:58 PM]

I believe it is some sort of character conversion routine, though I''ve never used Win32, so don''t quote me on that.

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blah blah blah.

Hm. We learn something every day. Interestingly obscure macro though, since msdn returned "CFileFind::GetLength (Visual C++ 6.0)" when searching for _T(
Anyone care to explain "L ## x"?

## is for concatenating things with the preprocessor. Better explanation is here.

Edit: L is for declaring wide-character strings (ie: unicode strings). So L ## x, with x being a #define for "hello", results in L"hello".

[edited by - dcosborn on May 14, 2004 9:59:15 PM]

Thanks! That was a quick response, I spent 15 minutes searching and gave up hehe.

Its quite obsqure, and undecriptive, that isn''t good...

quote:

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Original post by Silverbolter
Thanks! That was a quick response, I spent 15 minutes searching and gave up hehe.

Its quite obsqure, and undecriptive, that isn't good...

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Don't forget the header file <tchar.h> for some more insights. Under unicode builds (UNICODE globally defined) those _T( "boo" ) strings turn into L"boo" strings which are stored in wchar_t's instead of char's (a wchar_t is a C++ 16-bit character type)

Muhammad Haggag,
Optimize
[edit]Angle brackets

[edited by - Coder on May 14, 2004 11:16:14 PM]

quote:

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Original post by Coder

quote:

---

Original post by Silverbolter
Thanks! That was a quick response, I spent 15 minutes searching and gave up hehe.

Its quite obsqure, and undecriptive, that isn't good...

---

Don't forget the header file <tchar.h> for some more insights. Under unicode builds (UNICODE globally defined) those _T( "boo" ) strings turn into L"boo" strings which are stored in wchar_t's instead of char's (a wchar_t is a C++ 16-bit character type)

Muhammad Haggag,
Optimize
[edit]Angle brackets

[edited by - Coder on May 14, 2004 11:16:14 PM]

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I suppose it would be a wchar_t * (like char *)? In which case, does std::string have unicode support?

[edit] After a bit of my own research, is it safe for me to say that std::string is unicode by default, and converts to "standard" ASCII strings when needed? Am I getting this all wrong?

Thanks to both dcosborn and AP for clearing up L ## x, by the way.

[edited by - jflanglois on May 15, 2004 1:02:56 AM]

You could just write:

L"some unicode string"

or:

"some non-unicode string"

but:

_T("some generic string")

Allows you to change the string type at compile time by changing the definition of _T via the UNICODE preprocessor definition and therefore allows you to write unicode-aware code that does not depend on unicode :-)

There is a rather lengthy explanation here:

http://www.rpi.edu/~pudeyo/articles/unicode.html

The answer to your question does std::string support UNICODE and the answer is ..... YES you just have to say wstring instead! If you don''t have the F1 key handy in Visual Studio here is some of the help on it:

typedef basic_string wstring;
Example
// string_wstring.cpp
// compile with: /EHsc
#include <string>
#include <iostream>

int main( )
{
using namespace std;
// Equivalent ways to declare an object of type
// basic_string
const basic_string s1 ( L"abc" );
wstring s2 ( L"abc" ); // Uses the typedef for wstring

// Comparison between two objects of type basic_string
if ( s1 == s2 )
cout << "The strings s1 & s2 are equal." << endl;
else
cout << "The strings s1 & s2 are not equal." << endl;
}
Output
The strings s1 & s2 are equal


Notice the lack of the _T( MYSTRING ) macro. You don''t need it but IMO I think it beats looking at L''s all over the place. Plus the macro is handy for converting back and forth from UNICODE to char. If you have Visual Studio .NET you can use wchar_t as a built in type. Just set it in your compiler project options. Here is an excerpt on wchar_t:
the type wchar_t becomes a native type that maps to __wchar_t in the same way that short maps to __int16

Armitage: You need to fix the angle brackets after basic_string.

quote:

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After a bit of my own research, is it safe for me to say that std::string is unicode by default, and converts to "standard" ASCII strings when needed? Am I getting this all wrong?

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typedef std::basic_string<TCHAR> tstring;
tstring boo( _T( "Some text" ) );  

When UNICODE is defined, "Some text" will be UNICODE-ified. Otherwise, it'll be ANSI-fied

Muhammad Haggag,
Optimize
[edit]Sheesh! Forgot about the angle brackets myself.

[edited by - Coder on May 15, 2004 1:53:13 AM]

OK, thanks for the replies. I don''t have MSVC help installed on MSVC.NET (it''s MSDNAA)

[Edited by - jflanglois on July 16, 2004 6:42:16 PM]

The MSDN documentation stuff is available through MSDNAA.

Yeah, for MSVC 6, I haven''t found it for .NET (or is it in another location?)