 # Recurrence 0.1.0

git clone git://github.com/EdvardM/recurrence.git

• Recurrence

** Overview

Recurrence provides a simple class for handling recurring,
time-associated
objects. The goal is to create a general-purpose,
loosely coupled class library to provide common functionality for events
occurring at predetermined intervals.

Short example:

require ‘recurrence’

first_of_june = [2008, 6, 1]
r = Recurrence.new(first_of_june, :every_other => :week, :until =>
‘2010-06-01’)

my_cal = MyCalendar.new_default
my_cal.each_day { |date|
time = Time.parse(date) # assuming date can be parsed with
Time.parse
puts ‘Yay! today is the day!’ if r.recurs_on?(time)
}

** Set-like operations

Real power of Recurrence lies in it’s support for set-like operations
+join+,
+intersect+, +diff+ and +complement+. For example,
given the start date of 2008-06-01, recur something every thursday and
friday:

require ‘recurrence’

start_date = ‘2008-06-01’
r1 = Recurrence.new(start_date, :every => :thursday)
r2 = Recurrence.new(start_date, :every => :friday)
r = r1.join(r2)

Another example, a tad contrived perhaps:

# Recur something every friday, except if it is last friday of the

month:

dow = :friday
r1 = Recurrence.new(:epoch, :every => dow)
r2 = Recurrence.new(:epoch, :every_last => dow, :of => :month)

r = r1.diff(r2)

Nested set-like operations are also possible. So, for arbitrary
recurrences a
and b and any time t, the following should always apply:

r1 = (a.join(b)).complement
r2 = (a.complement).intersect(b.complement)

r1.recurs_on?(t) == r2.recurs_on?(t) # De Morgan’s law - complement of
a
union is the same as intersection of the complements

See RecurrenceBase::SetOperations for more.

** Installation

Enter

rake gem

on the command line in the same directory as this README file, it should
produce the gem under the pkg directory.
Then you should be able to say

sudo gem install pkg/recurrence*.gem

to install the gem to your local system.

KTHXBAI