class Array
  # Fetch values from a start index thru an end index.
  #
  #   require 'facet/array/upto'
  #
  #   [1,2,3,4,5].thru(0,2)  #=> [1,2,3]
  #   [1,2,3,4,5].thru(2,4)  #=> [3,4,5]
  #
  def thru( from, to )
    a = []
    i = from
    while i <= to
      a << self.at(i)
      i += 1
    end
    a
  end
end