aaa.rb

class Array
  def odd_values
    e = [false, true].cycle
    select { e.next }
  end
  def even_values
    e = [true, false].cycle 
    select { e.next }
  end
  
  def odd_and_even_values
    odd = []; even = []
    e = [even, odd].cycle
    each { |i| e.next << i }
    [odd, even]
  end
end