Re: [boost] How to represent underspecified Date in boost::date_time library?

From: Martin Min (lingvisa_at_[hidden])
Date: 2007-07-11 15:50:23

Thanks, Jeff. Your proposals make sense and I will think more on this.
Martin

On 7/11/07, Jeff Garland <jeff_at_[hidden]> wrote:
>
> On Wed, 11 Jul 2007 13:34:22 -0500, Martin Min wrote
> > Jeff:
> > Thanks for your reply.
> > First, by "You can use gregorian::greg_year which is the first
> > parameter to a date", do you mean a date can be constructed by just
> > passing greg_year? or still I have to provide a month and day?
>
> What I mean is you can just use greg_year to represent the year instead of
> the
> date class.  However, given your requirements below it probably won't be
> of
> much help.
>
> >  I am working in  Natural  Language  Understanding area,  in which
> > underspecifed Temporal Expressions abound in typical news text, and
> > reasoning on these type of knowledge often has to deal with
> > incomplete information.  The granularity (or resolution) of time
> > often changes in a discourse, sometimes year, or month, or date, or
> > time, even century.
>
> I see.
>
> > What I like most boost::date_time are the various arithematic
> > operations on durations and date periods, and timezone support. Of
> > course, as well as the robustness.
> >
> > Probably, what I can do is to define another Date class, which have the
> > boost::date_time::date has a member, and add members I may need?
>
> Possibly.  It seems like you might need something a bit different -- a
> multi-resolution time point.  Or you need to have series of different time
> points with different resolutions.  For example you could have something
> like
> this:
>
>   boost::gregorian::date; //time point with 1 day resolution
>   class month_year;       //time point with 1 month resolution
>   class quarter;          //time point with 3 month resolution
>   class year;             //time point with 1 year resolution
>   class decade;           //time point with 10 year resolution
>   class century;          //time point with 100 year resolution
>
> So, simple usage would look something like:
>
>   month_year my(2007, Jul);
>   quarter q(2007, 2);
>   year y(2007)
>   decade d(21, 1); //21st century, 1st decade
>   ....
>
> Of course the alternative is to have a single type that provides the
> something
> like this:
>
>    //pseudo code
>    class general_time_point
>    {
>      enum TIMEPOINT_RESOLUTION { DAY, MONTH, YEAR, QUARTER, DECADE,
> CENTURY}
>      general_time_point(year, month, day);
>      general_time_point(year, month);
>      general_time_point(value, TIMEPOINT_RESOLUTION); //general
> constructor
>    };
>
>
>
> So if you had one of these 2 kinds of types, what would you like to do
> with
> them?  There a conceptual issues w.r.t the meaning of arithmetic
> operations on
> these kinds of types.  For example:
>
>     decade c(21, 1);
>     c += days(1);  //meaningless
>     year y(2007)
>     y += years(2); //ok
>
> The advantage of the multi-type solution is that the meaningless
> operations
> can be prevented at compile time.  However, the multi-type solution is
> likely
> more difficult in your particular case.
>
> Jeff
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