Notes + operator

notes.rb

def +(other)
  new_data = data.merge(other.data) do |_, val, other_val|
    case val
    when Array, Integer
      val + other_val
    when Hash
      val.merge(other_val) { |__, val1, val2| val1 + val2 }
    else
      nil
    end
  end
  self.class.new(new_data)
end