Re: [boost] date_time: second_clock and microsec_clock errors

From: Jeff Garland (jeff_at_[hidden])
Date: 2005-11-28 08:36:43

On Mon, 28 Nov 2005 15:20:47 +0200, Roman Yakovenko wrote
> > [mailto:boost-bounces_at_[hidden]]On Behalf Of Jeff Garland
> > > [micro]second_clock< boost::local_time::local_date_time_base<> > 
> > > could not be compiled. The problematic function is: private: static 
> > > time_type create_time(::std::tm* current);
> > > 
> > > The error is that local_date_time_base<> does not have constructors 
> > > that takes date and time duration.
> > 
> > It's not really a problem.  With local_time you need to 
> > provide a timezone
> > pointer to get a time value.  So you call it like this:
> >   //get time in new york time zone:
> >   boost::shared_ptr<time_zone> ny_tz(new
> > posix_time_zone("EST-05EDT,M4.1.0,M10.5.0"));
> > 
> >   local_date_time ldt3 = local_microsec_clock::local_time(ny_tz);
> > 
> > 
> > You'll note that there is another overloading in clock 
> > classes for this case:
> > 
> >   template<class time_zone_type>
> >   static time_type local_time(shared_ptr<time_zone_type> tz_ptr);
> 
> Yes, I discovered work around few days ago. 
> I posted the error here, because I think that this error indicates,
> that something wrong with design.

Anything's possible ;-)
 
> I think that date_time library should define local_microsec_clock,
> not in terms of microsec_clock, but using an other class that is 
> aware of time zone. 
> 
> Why is microsec_clock class not aware of time zones?

I'll turn it around the other way.  Most instances of microsecond_clock never
care about the a time_zone to adjust the time.  So there is no reason to drag
in that dependency.  But, in fact, the overloading I pointed out above:

  template<class time_type>
  class microsecond_clock {
  ...
   template<class time_zone_type>
   static time_type local_time(shared_ptr<time_zone_type> tz_ptr);

enables the microsecond clock to use a time zone.  When using a
local_date_time type the timezone is required.  So it's true, you'll get a
compile error if you try to call the other overloadings with a
local_date_time, but that's the intent.  

Jeff