Re: [Boost-users] date_time question

From: Arkadiy Vertleyb (vertleyb_at_[hidden])
Date: 2006-09-20 15:31:46

"Jeff Garland" <jeff_at_[hidden]> wrote

> Arkadiy Vertleyb wrote:
>> Hi,
>>
>> I am looking at the possibility of replacing our custom-made datetime
>> classes with the ones from boost::date_time.  The library looks very
>> attractive to me, and I would certainly go ahead and use it...  however
>> there is (at least) one catch, and this is the snap-to-end-of-month 
>> behavior
>> of the months duration, according to which:
>>
>> {2000-Feb-29} + {1 month} = {2000-Mar-31}
> >
>> The problem is that it contradicts to the XSD spec we are using,
>> http://www.w3.org/TR/2001/REC-xmlschema-2-20010502/#adding-durations-to-dateTimes,
>> that says that months must be just "pinned to be within range".  Maybe 
>> there
>> is (could be added) some sort of policy, that could be used to achieve 
>> this
>> behavior?
>
> I've tried to read this algorithm before and I have to say I've never 
> fully
> understood it.  As for policies, the implementation is already policy 
> based.
> You could write a new month_functor class to replace the one that the 
> library
> uses.  The signature is
>
>
>   template<class date_type>
>   class month_functor
>   {
>   public:
>     duration_type get_offset(const date_type& d) const
>     {}
>     duration_type get_neg_offset(const date_type& d) const
>     {}
>
> Where get_neg_offset handles subtraction and get_offset is for addition. 
> You
> can see date_time/adjust_functors.hpp for the current implementation. 
> After
> you write your new function you'll need to create your own duration types 
> or
> replace the ones in date_time/gregorian/greg_duration_types.hpp so that 
> you
> can do cool stuff like:
>
>   date d(2000,3,31);
>   d += months(3);

OK, thanks, I'll look at this.

Regards,
Arkadiy