Really great Paul.

Did you compared your Spanish classes examples with org-diary-class? Maybe
(I did not tried!) your proposal is an improvement of this function.

Thank you/ Gracias,

Daniel



2010/8/18 Noorul Islam K M <noorul@noorul.com>

> I think it will be great if this goes into worg?
>
> - Noorul
>
> On Aug 19, 2010, at 1:52 AM, Paul Sexton <psexton@xnet.co.nz> wrote:
>
> > In org, timestamps can be in the usual angle-bracket format,
> > eg <2010-08-19 +2w>, or you can use lisp s-expressions. These are in the
> same
> > format as the s-expressions used in the 'diary'/'calendar' emacs
> packages. I
> > only discovered these recently but have been able to use them to schedule
> some
> > complex recurring items. I thought I would share the code here.
> >
> > 1. Recurring items with a limited number of occurrences
> >
> > For example, say you are taking night classes in Spanish. The class is
> every
> > Wednesday evening at 7pm, starting on 18 August, and runs for 8 weeks.
> AFAIK
> > Org's timestamps do not support limited occurrences of recurrent items --
> you
> > have to schedule the item with infinite recurrences, then delete it when
> it
> > finishes.
> >
> > To schedule the Spanish classes, put the following in your .emacs:
> >
> > (defun diary-limited-cyclic (recurrences interval m d y)
> >  "For use in emacs diary. Cyclic item with limited number of recurrences.
> > Occurs every INTERVAL days, starting on YYYY-MM-DD, for a total of
> > RECURRENCES occasions."
> >  (let ((startdate (calendar-absolute-from-gregorian (list m d y)))
> >        (today (calendar-absolute-from-gregorian date)))
> >    (and (not (minusp (- today startdate)))
> >         (zerop (% (- today startdate) interval))
> >         (< (floor (- today startdate) interval) recurrences))))
> >
> > The item in the org file looks like this:
> >
> >
> > ** 19:00-21:00 Spanish lessons
> > <%%(diary-limited-cyclic 8 7 8 18 2010)>
> >
> >
> > 2. Public holiday that is "the nearest Monday to DATE"
> >
> > In New Zealand each regional capital has an "Anniversary Day". The date
> of
> > Auckland's anniversary day is "the nearest Monday to 29 January".
> >
> > Put this in your .emacs:
> >
> > (defun calendar-nearest-to (target-dayname target-day target-month)
> >  "Recurring event that occurs in the nearest TARGET-DAYNAME to
> > the date TARGET-DAY, TARGET-MONTH each year."
> >  (interactive)
> >  (let* ((dayname (calendar-day-of-week date))
> >         (target-date (list target-month target-day (calendar-extract-year
> date)))
> >         (days-diff (abs (- (calendar-day-number date)
> >                            (calendar-day-number target-date)))))
> >    (and (= dayname target-dayname)
> >         (< days-diff 4))))
> >
> > Now we can schedule Auckland Anniversary Day. The first argument, 1,
> means
> > Monday (days of the week are numbered starting with Sunday=0).
> >
> >
> > *** Auckland Anniversary Day
> > <%%(calendar-nearest-to 1 29 1)>
> >
> >
> > 3. Public holiday on "the 4th Monday in October".
> >
> > This does not require any additions to .emacs:
> >
> >
> > *** Labour Day (NZ)
> > <%%(diary-float 10 1 4)>
> >
> >
> > 4. Easter
> >
> > Easter's date moves around from year to year according to a complicated
> set of
> > criteria which I do not claim to understand. However the following code
> will
> > allow you to schedule recurring events relative to Easter sunday.
> >
> > Note: the function da-easter is from:
> > http://github.com/soren/elisp/blob/master/da-kalender.el
> >
> > Put the following in your .emacs:
> >
> > (defun da-easter (year)
> >  "Calculate the date for Easter Sunday in YEAR. Returns the date in the
> > Gregorian calendar, ie (MM DD YY) format."
> >  (let* ((century (1+ (/ year 100)))
> >         (shifted-epact (% (+ 14 (* 11 (% year 19))
> >                              (- (/ (* 3 century) 4))
> >                              (/ (+ 5 (* 8 century)) 25)
> >                              (* 30 century))
> >                           30))
> >         (adjusted-epact (if (or (= shifted-epact 0)
> >                                 (and (= shifted-epact 1)
> >                                      (< 10 (% year 19))))
> >                             (1+ shifted-epact)
> >                           shifted-epact))
> >         (paschal-moon (- (calendar-absolute-from-gregorian
> >                           (list 4 19 year))
> >                          adjusted-epact)))
> >    (calendar-dayname-on-or-before 0 (+ paschal-moon 7))))
> >
> >
> > (defun da-easter-gregorian (year)
> >  (calendar-gregorian-from-absolute (da-easter year)))
> >
> > (defun calendar-days-from-easter ()
> >  "When used in a diary sexp, this function will calculate how many days
> > are between the current date (DATE) and Easter Sunday."
> >  (- (calendar-absolute-from-gregorian date)
> >     (da-easter (calendar-extract-year date))))
> >
> > Now we can schedule the public holidays associated with Easter as
> > recurring events. Good Friday is 2 days before "Easter", Easter Monday is
> one
> > day after.
> >
> >
> > *** Good Friday
> > <%%(= -2 (calendar-days-from-easter))>
> >
> > *** Easter Sunday
> > <%%(= 0 (calendar-days-from-easter))>
> >
> > *** Easter Monday
> > <%%(= 1 (calendar-days-from-easter))>
> >
> >
> > Paul
> >
> >
> >
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