On 2/9/2014 10:58 PM, Vladimir Batov wrote:
Another day I came across a topic called "String to T conversions - getting it right this time http://groups.google.com/a/isocpp.org/group/std-proposals/t/a9905ba8e4f33f3e" on the "ISO C++ Standard - Future Proposals https://groups.google.com/a/isocpp.org/forum/#%21forum/std-proposals" that got me interested/curious. Unfortunately, it seemed more of a discussion rather than a proposed/deployable solution to the string conversion issue. Then, I searched Boost archives to see if there was any development in that string-to-type conversion domain since my unsuccessful proposal about three years ago:
From: Edward Diener
Subject: [Review] Boost.Convert, review manager analysis http://news.gmane.org/find-root.php?message_id=iq12fm%24k6c%241%40dough.gman... Newsgroups: gmane.comp.lib.boost.devel http://news.gmane.org/gmane.comp.lib.boost.devel, gmane.comp.lib.boost.user http://news.gmane.org/gmane.comp.lib.boost.user Date: 2011-05-06 15:01:06 GMT (2 years, 39 weeks, 6 days, 23 hours and 47 minutes ago)
Unfortunately I was not able to find anything. Apologies if I missed something major/serious (I was not exactly closely monitoring the list). Is anyone aware of any work done in the area? If not, then I am thinking if we could revisit the issue the original (and failed) Boost.Convert tried to address. I am not sure about others but for me that quite essential and seemingly simple task is still quite important. I was watching the development of the lexical_cast but did not see it going beyond its original frugal design. So, maybe we might have another look at the code that Boost.Convert has become and that I've been using/working on?.. Convert V2... From past experience calling it Boost.Convert seems quite premature. :-) I only put Boost.Convert in the title as a reminder for those who participated in the original review.
So, the code is at https://github.com/yet-another-user/boost.xtra. The docs are old (from the original proposal) so, if anyone interested, I'd suggest jumping right to the test/example code in libs/convert/test. Apologies for the inconvenience but for now I'll try to see if I should put any effort updating the docs for possible submission.
I would strongly suggest updating the docs for the library. Also either add in to the new docs the differences between the original version and the new version, or just include both the old and new version docs so that end-users could easily see what has changed. I would be glad to be the review manager of the new library, if necessary, if you wanted the new library added to the Boost review queue once you felt everything was complete. OTOH I would also understand if you wanted someone else to be the review manager.
The main difference from the original proposal is that the complicated blob was split in to two separate components -- Convert API facade and a converter. Here it seems very similar to (same as?) boost::lexical_cast which provides a uniform API facade which in turn deploys additional functionality (op<<, op>>). Similarly, Convert V2 requires a converter to be specified for conversion:
boost::cstringstream_based_converter ccnv; // char converter boost::wstringstream_based_converter wcnv; // wchar_t converter
Then,
int a000 = convert<int>::from(not_int_str, -1, ccnv); int a001 = convert<int>::from(std_str, -1, ccnv); int a002 = convert<int>::from(c_str, -1, ccnv); int a003 = convert<int>::from(wstd_str, -1, wcnv); int a004 = convert<int>::from(wc_str, -1, wcnv);
Now all the configuration (formatting, locales, etc.) is separate from the API facade and provided (or not) by the plugged in converter. The only available converter tringstream_based_converter allows something like:
std::locale rus_locale (rus_locale_name); std::locale eng_locale ("");
// Set locale, case, precision, ccnv(std::setprecision(4))(std::scientific)(std::nouppercase);
string double_rus = convert<string>::from(double_v01, ccnv(rus_locale)).value(); string double_eng = convert<string>::from(double_v01, ccnv(eng_locale)).value();
Offhand this looks better. As I recall a general criticism was that you were trying to do too much in the convert library rather than just focusing in on 'convert' as a better, more flexible replacement than lexical_cast. Sometimes les is more <g>.
Gosh, it's getting too long... cutting it short. The above is probably sufficient for those who participated in the original review. Those who did not might have a look at the (original and old) docs and the test/example code.