TODO list for Perl module DateTime-Event-ICal

* optimize byday=>['we','fr'] - a lot!
  DONE:
    - byday with many options makes tests very slow 
      see: t/rfc2445.t tests 34, 35
    - bysetpos might get faster if it used 'next'/'previous'
      instead of 'intersection' - may need memoization
  TODO:
    - use this algorithm when there are more arguments.

* sub _recur_1fr()
  - make it accept 'FR' (it only accepts '1FR' style)
  - test: freq=>yearly byday=>we

* "byday -2 friday"
  - test overflow
  - need some 'interval' and 'dtstart' tests

* the implementation of 'select' in Set::Infinite is incomplete
  and doesn't have the 'last' attribute. -- should be implemented!
  Note: this is not a problem because it is only used in 'count', 
        which generates finite sets. 

* finish importing Date::Set RFC2445 recurrence tests

* bysetpos
  - use some kind of memoization

* byweekno - test with 'daily'

* no tests were made defining recurrences without dtstart.

* the effect of 'count' on a recurrence without dtstart is not defined.
  the effect of count == 0 is not defined.

* no tests were made using datetimes with timezones.

* mixing positive and negative arguments in the same list
  might give wrong results is the numbers are big enough
  to cause the datetimes to interleave.
  - split in two recurrences and join with 'union'

* some arguments are not checked for overflow,
  such as byyearday.

