in_groups (ActiveSupport::CoreExtensions::Array::Grouping)

    # 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