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.

Alternatively, you can pull gem from the github:

1. Add github gems to your gem sources (you can skip this if you have done so already)

sudo gem sources -a http://gems.github.com

1. sudo gem install EdvardM-recurrence

KTHXBAI

License

MIT (see MIT-LICENSE)