String L or without L

HelloWorld · #1 (**permalink**) 11-19-2007, 12:40 AM

What is the difference between

Code:

L"Hello World"

and

Code:

"Hello World"

...??? thx

Bench · #2 (**permalink**) 11-30-2007, 04:10 AM

the L character indicates that the string literal is a "wide string literal". In other words, an array of wchar_t rather than just plain old char.

the 'wide char' is usually used for internationalisation, where you might want to use unicode instead of standard 1-byte characters.
(Note - the size of wchar_t is not 'set in stone', though on most systems I'm aware of, it usually supports at least UTF-16)

the C++ library has a whole bunch of wide character tools, all of which are similar to their 'narrow character' equivalents, but prefixed with a w. eg, wcout, wstring, wcin, etc.

HelloWorld · #3 (**permalink**) 11-30-2007, 08:14 PM

so, is it a good practice to keep L in tag every time we're writing a string? If not, then what's the point of having one kind over the other? I personally think that internationalization is an important part of codes...

Bench · #4 (**permalink**) 12-01-2007, 03:56 AM

Not really - wide character strings aren't just a simple modification of adding L's to your program. you need to use the wide character string type and related I/O streams too.

There's no point in storing simple strings (eg, "hello") in wide character format - since not only does it complicate things (wchar_t has no standard defined size, and its representations vary), it usually uses more bytes than necessary too.

Internationalisation extends beyond wide characters into areas such as number representation, date representation, etc. The usual approach is to write the user interface portion separately, then only the UI will be concerned with these issues, allowing the rest of the program to continue internally without having to worry about how it looks to the outside world.

If you want to make a habit of using wchar_t for everything, then feel free. although the more common approach is a conversion function to widen or narrow strings as you need to. eg,

Code:

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

std::wstring widen_string(std::string str)
{
    std::wstring result;
    std::locale loc;
    for(int i(0); i < str.size(); ++i)
    {
        result += std::use_facet<std::ctype<wchar_t> >(loc).widen(str[i]);
    }
    return result;
}

int main()
{
    std::string str = "hello, world";

    std::wcout << widen_string(str);
}

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