Re: [boost] [locale] Review. Internationalization library?

Subject: Re: [boost] [locale] Review. Internationalization library?
From: Vicente BOTET (vicente.botet_at_[hidden])
Date: 2011-04-16 12:30:20

> Message du 16/04/11 15:22
> De : "Artyom" 
> A : boost_at_[hidden]
> 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