Message du 16/04/11 15:22 De : "Artyom" A : boost@lists.boost.org Copie à : Objet : Re: [boost] [locale] Review. Internationalization library?
Why have you preferred to redo Boost.DateTime?
If the DateTime library is redone, shouldn't it be released as a separated one, DateTime2?
No, because they have very different purposes.
There is almost no locale dependent libraries in Boost while boost::locale::date_time is strictly locale dependent.
It provides same interface for different calendars and they may be changed in the runtime.
I think that internationalization is a traversal concern that could be applied to a lot of libraries. For example, it could be applied to Boost.Ratio, Boost.Chrono, Boost.Units. This doesn't means that all these libraries must be inside Boost.Locale/I18N. So yes, I'm sure that it will be better you provide a separate proposal for, let me say, Boost.Calendar or Boost.Dates that will use whatever is needed to make dates, calendars internationalizable.
Do your classes preserve the same interface than Boost.DateTime?
If not, does the documentation show the differences in a specific section?
Actually almost everything there is different:
http://cppcms.sourceforge.net/boost_locale/html/dates_times_timezones.html
I see this know.
If we follow the Chrono design, shouldn't the calendar be a template parameter of the dattime class?
What about rewriting the following
date_time some_point = period::year * 1995 + period::january + period::day*1;
as
date_time some_point = year(1995) + january + day(1);
?
Actually it may be good idea. I'm already thinking on improvement of date_time API due to issues rise in the review and it seems that it may be one of the approaches,
Why your datatime class output by default as a number? Why there is no a default format?
Because date_time is approximately a number that represents a time point in UTC (POSIX time) - seconds since Jan 1, 1970 GMT without leap seconds.
boost::time_point<> is also an opaque number. This doesn't mean that it is anumber. This doesn't explain why a default other than a raw number is not better. I would expect that it outputs as a date + a day time.
But it under the hood it allows to perform date-time calculations according to current locale's rules.
It outputs number because "it is a number of seconds since..." and the actual stream formatters are responsible to formatting it.
It is covered by the links above.
Basically there is a separation of roles:
- date_time calculates times - iostream formats numbers - numeric representation connects between them.
I don't see an explanation to choose as default the hidden representation. By the way, i would be interested in adapting Boost.Chrono to use Boost.Locale/I18N. Maybe a future Boost.Calendar library would use Boost.Chrono. Best, Vicente