gistfile1.rb

class Array
  def each_slice_with_index(slice_size)
    nb_slices = (self.size.to_f/slice_size).ceil
    for i in 0...nb_slices
      yield self[i*slice_size,slice_size], i
    end
  end

  def each_slice_with_index_alt(slice_size)
    slices = self.enum_slice(slice_size).map
    slices.each_with_index { |slice,index| 
      yield slice,index
    }
  end
end