Re: boost support for date/time handling?

From: bill_kempf (williamkempf_at_[hidden])
Date: 2001-12-20 11:04:27

--- In boost_at_y..., "Dave Gomboc" <dave_at_c...> wrote:
> > Sorry, I'm not sure whether I understand. Would you use TWO
> > datetime_instant objects (or one instant and one span?) to 
represent
> > December 17, 2001? What advantage does this have? Please give an
> > example.
> 
> Neither.  I'd use one datetime_range.

Rarely do I use a datetime_range type of concept.  I usually work 
with either a datetime_instant or a datetime_duration.  I realize 
that other people's needs will vary from mine, but forcing me to use 
a datetime_range to indicate either of the other two (how can a range 
accurately represent a duration?) would just make my life miserable.

> Clearly, when working just with days, one can use datetime_instant 
and
> forget about it.  But when working with a mixture of single days, 
ranges
> of days, months, years, you name it, I've found it much more 
convenient
> to simply treat everything as ranges of datetimes.  In that case, 
the
> day of December 17 would be represented publicly as:
> 
>   datetime_range.begin()    => December 17, 2001, 12:00am
>   datetime_range.end()      => December 18, 2001, 12:00am
>   datetime_range.duration() => 1 day

So make your datetime_range constructible frome a datetime_instant.  
This makes your life easy while not complicating mine.  Further, 
having individual concepts for all three types allows for use of more 
strongly typed operations.  If I need to set the birth_date for an 
employee the operation should take a datetime_instant insuring that a 
user doesn't pass in a three day range.

I see a need for three types (not suggesting these as the names, 
though):

datetime_range
datetime_instant
datetime_duration

I don't see a need for a seperate date or time type.  The 
datetime_instant can default the time to midnight and be used for 
dates.  The time type is really a datetime_duration (it's the amount 
of time that's passed within an arbitrary given day).

Bill Kempf