# File lib/active_support/core_ext/array/grouping.rb, line 59
        def in_groups(number, fill_with = nil)
          # size / number gives minor group size;
          # size % number gives how many objects need extra accomodation;
          # each group hold either division or division + 1 items.
          division = size / number
          modulo = size % number

          # create a new array avoiding dup
          groups = []
          start = 0

          number.times do |index|
            length = division + (modulo > 0 && modulo > index ? 1 : 0)
            padding = fill_with != false &&
              modulo > 0 && length == division ? 1 : 0
            groups << slice(start, length).concat([fill_with] * padding)
            start += length
          end

          if block_given?
            groups.each{|g| yield(g) }
          else
            groups
          end
        end