From: Stefan Salewski <mail@...>
Date: 2013-10-22T17:56:36+02:00
Subject: [ruby-core:57975] Module Enumerable -- each_cons() ==> each_cycle()

Hello,

I would really love to have a cyclic version of each_cons in Ruby --
I found the version below, which seems to work fine for me. I think that
method is not too exotic, so it may be good to have this built in.

https://www.ruby-forum.com/topic/106362

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

Then you can each_cycle anything that is Enumerable, like a Range:
 >> (1..5).each_cycle(3) {|x| p x}
[1, 2, 3]
[2, 3, 4]
[3, 4, 5]
[4, 5, 1]
[5, 1, 2]
=> 1..5
 >> { 'dog' => 'Rover', 'cat' => 'Mittens', 'fish' =>
'Goldie' }.each_cycle(2) {|x| p x}
[["cat", "Mittens"], ["fish", "Goldie"]]
[["fish", "Goldie"], ["dog", "Rover"]]
[["dog", "Rover"], ["cat", "Mittens"]]
=> {"cat"=>"Mittens", "fish"=>"Goldie", "dog"=>"Rover"}