gistfile1.txt

  def self.group_by(method_name)
    define_method :"group_by_#{method_name}" do
      inject([]) do |_, v|
        k = yield(v)
        if _.empty? || !_.last.send(method_name, k)
          _ << [v]
        else
          _.last << v
        end
        _
      end
    end
  end
  
  group_by :first # --> def group_by_first
  group_by :includ? # --> def group_by_include?