Array#modulo.rb

class Array
  # If you want the first n items from an array, you could call first(n)
  # but if the array has less than n members, so will the return value.
  # This method ensures that the return value has as many items as requested,
  # by cycling through the array from the beginning. 
  # e.g. [1,2,3].modulo(2) => [1,2]
  #      [1,2,3].modulo(4) => [1,2,3,1]
  #      [1,2,3].modulo(7) => [1,2,3,1,2,3,1]
  def modulo(required_size)
    required_size = size if required_size.nil?
    if required_size <= size
      first(required_size)
    else
      multiplier = required_size / size
      oversized = self * (multiplier + 1)
      oversized.first(required_size)
    end
  end
end