On Fri, Aug 12, 2011 at 15:04, Matus Chochlik <chochlik@gmail.com> wrote:
On Fri, Aug 12, 2011 at 1:08 PM, Yakov Galka <ybungalobill@gmail.com> wrote:
On Fri, Aug 12, 2011 at 12:00, Matus Chochlik <chochlik@gmail.com> wrote:
On Fri, Aug 12, 2011 at 9:57 AM, Daniel James <dnljms@gmail.com> wrote:
On 11 August 2011 12:57, Artyom Beilis <artyomtnk@yahoo.com> wrote:
[...]
// by default expect UTF8 text(const std::string& str) { assert(is_utf8(str.begin(), str.end())); store(str); }
What you are doing is, in fact, forcing the assumed encoding of std::string to UTF-8. You just said you think it's a bad idea.
No, I'm proposing to implement a *new* class that will store the text in UTF8 encoding and if during the construction no encoding is specified, then it is assumed that the particular std::string is already in UTF8.
This is *very* different from imposing an encoding on std::string which is already used in many situations with other encodings. i.e. my approach does not break any existing code.
Sorry, your arguments start to look non-constructive to me. Correct me where I'm wrong in the following reasoning. (1) You object to UTF-8 strings in boost interface because someone may pass something other than UTF-8 there and it's going to be undetected at compile time: namespace boost { void func(const std::string& a); } // UTF-8 boost::func(non_utf_string); //oops You're proposing a `text` class that is meant to somehow overcome this problem. So you change the boost interface to accept `text` but user code is left unchanged...: namespace boost { void func(const text& a); } boost::func(non_utf_string); //oops, the std::string default constructor is called. Yes, you can make this constructor explicit, so the above code stops compiling and the user must write explicitly: boost::func(text(non_utf_string)); But then there is nothing in your proposal that makes std::string utf-8 encoded by 'default'. Default == implicit. [...]
I believe that it is more generic to use a combination of function + tag than just a function because there are other APIs besides the OS's that use various encodings and my approach scales better.
r do you like from_narrow_os(), from_wide_os(), from_narrow_stdlib(), from_narrow_lib1(), ... from_wide_libN(); more ?
(2) No, I'd never proposed that. I repeat this again: The only encodings which matter are 'system default', UTF-8, and UTF-16. I would like to see a list of widely used libraries which use other encodings, please. [ Note: Not including libraries used for encoding conversions. — end note. ] Even if there is such a library out there, the user is *already* converting to/from its exotic encoding.
[...] Besided it does not harm you in any way
It does. I already use UTF-8 for all my strings, even on windows, and I don't want the code-bloat of all these conversions (even if they're no-ops).
[...]
string t6 = from_narrow(pq_some_func());
As you start using more libraries with UTF-8 default encoding, you will
use
from_* less frequently. (It's possible to use a single to_utf8 instead of from_narrow/from_wide combination.)
The approach that I proposed *does not* force you to specify the utf8 encoding explicitly neither if you are 100% sure that the string is in UTF8 and that this does not change under any circumstances (like when somebody changes the locale)
Huh? Neither mine. Again, what you say here contradicts (1).
[...] And what if t8 was read from another source (not UTF8 and not WINAPI) which may for example use the locale's encoding or some arbitrary encoding?
See (2). [...]
You need to specify the source from which the text comes (by the symbolic tag) and the library handles the details for you. If the source is UTF8 do nothing otherwise do the transcoding.
So can I summarize this debate as 'the programmer specifies the library and boost chooses the encoding' versus 'the programmer goes to the documentation of the library and says boost what encoding to use'? If yes, then it's a quite minor design decision. According to (2) I claim that there will be less encodings than libraries. And by doing to_narrow/from_narrow
you are trying to do that "transparently". But again, that are other sources of text which use other encodings, besides the OS API.
See (2).
Boost libraries (at the very least those wrapping OS functionality)
should adopt this text class, and do the conversions, "just-in-time" when making the OS API call.
In the light of the said above, your 'text' class won't catch bugs like:
char str[1024]; GetWindowTextA(hwnd, str, sizeof(str)); boost::function_with_text_parameter(str);
No I didn't suggest doing it this way so sorry but this is strawman. This should look like:
char cstr[1024]; GetWindowTextA(hwnd, cstr, sizeof(cstr)); text str(cstr, textenc::winapi()); boost::function_with_text_parameter(str);
Neither I suggested passing non-utf-8 string to a utf-8 assumed string. It's not about the way you proposed to write the code, it's about your proposal doesn't solve the problem it was advocated to solve and be better from Artyom's and my proposal. See (1). You say that there is some code that you don't want to break, code you want to be compatible with. Which code? This code: char str[1024]; GetWindowTextA(hwnd, str, sizeof(str)); boost::function_with_text_parameter(str); // currently assumes system encoding Let's leave aside the fact that this code uses deprecated winapi interface and thus unicode-unaware. Yes, it *should* be written as: char cstr[1024]; GetWindowTextA(hwnd, cstr, sizeof(cstr)); text str(cstr, textenc::winapi()); boost::function_with_text_parameter(str); BUT (!!!), until the user rewrites this code, you've silently broke his code. This is *exactly* the same situation as assuming std::string is utf-8 in the first place, and your way of how the user had to write his code is almost the same as mine: char str[1024]; GetWindowTextA(hwnd, str, sizeof(str)); boost::function_with_text_parameter(from_narrow(str)); // accepts UTF-8 std::string // versus: boost::function_with_text_parameter(text(str, textenc::winapi)); // accepts your::text (3) The only way to avoid silent breakage is to trap it at compile time through disabling the implicit conversion from string and char*. (!!!) By making the constructor explicit you just break user-code at compile time rather than (silently) at run-time. Indeed it's a bit better than assuming utf-8 by default, but now your string is going to be hell to use, even for those who already use utf-8 encoded std::strings: std::string str = get_utf_8_string(); boost::function_with_text_parameter(str); // error, explicit constructor of text not called. please specify you intent. boost::function_with_text_parameter(text(str)); // wait, don't we want to encourage utf-8 std::strings? -- Yakov