Sheldon's exercise

array_extension.rb

class Array
  def sum
    sum = 0
    self.each do |item|
      #some code
    end
    sum
  end

  def add_index
    item_with_index_array = []
    self.each_with_index do |item, index|
      #some code
    end
    item_with_index_array
  end
end