# Python でもこんな感じのものを定義して
# ["<a>" + e + "</a>" for e in r(['root1', ['branch0', 'branch1'], 'root2', ['branches'] ])]
# って書きたい
class Array

  def r &blk
    [].tap { |res|
      each { |e|
        if e.is_a? Array
          res << e.r(&blk)
        else
          res << blk.call(e)
        end
      }
    }
  end

end

if __FILE__ == $PROGRAM_NAME
  require "test/unit"
  class TestR < Test::Unit::TestCase
    def test_r
      assert_equal ['root1', ['branch0', 'branch1'], 'root2', ['branches'] ].r { |e|
        '<a>' + e + '</a>'
      }, ["<a>root1</a>", ["<a>branch0</a>", "<a>branch1</a>"], "<a>root2</a>", ["<a>branches</a>"]]
    end
  end
end