enumerable_cyclic_extensions.rb

# http://blade.nagaokaut.ac.jp/cgi-bin/scat.rb/ruby/ruby-talk/249436
class Array
  def each_cycle(window, start=0)
    (start...length+start).each do |i|
      yield((i..i+window).map {|n| self[n % length]})
    end
  end
end

# Something a little more complicated from
# http://talklikeaduck.denhaven2.com/2007/04/30/our-kind-of-ducks-odd-ducks-and-trained-ducks
module Enumerable
   def each_cycle(window, start=0)
     wrap_start = []
     cache = []
     each_with_index do |e,i|
       cache << e
       if i >= start + (window - 1)
         yield cache[start, window]
         cache.shift
       else
         wrap_start << e
       end
     end
     wrap_start.each do |e|
       cache << e
       yield cache[start, window]
       cache.shift
     end
     self
   end
end