RFC: conditional DateTime::Set->add_duration

[Flavio S. Glock]

(Repost - was: Re: RFC Events Calendar)

Flavio S. Glock wrote:
> 
> How about having a generic method that anticipates or
> postpones an event, if it falls in an invalid date.
> For example:

  $payday_set = DateTime::Event::Recurrence->monthly(
      days => -1,
  );
 
  $weekend_set = DateTime::Event::Recurrence->weekly(
      days => [ 6, 7 ],
  );

>   # subtract days from "payday" events,
>   # such that they never fall in a weekend
>   $payday_set->add_duration_while(
>       condition => $weekend_set,
>       duration => DT::Duration->new( days => -1 ),
>   }

Result: $payday_set is a set of "last day of the month that is not a
weekend"

You can already do this using a DateTime::Event::ICal specification, but
'add_duration_while' is more powerful.

Another example: postpone payday if it is a weekend:

   $payday_set->add_duration_while(
       condition => $weekend_set,
       duration => DT::Duration->new( days => 1 ),
   }

- Flavio S. Glock