用block实现array的map select方法

  class Array
    def my_map(&block)
      new_array = []
      self.each do |e|
        new_array << block.call(e)
        # new_array << yield(e)
      end
      new_array
    end

    def my_select
      new_arr = []
      self.each do |e|
        new_arr << e if yield(e)
      end
      new_arr
    end
  end