RubyでScalaのIterator#slidingを実装してみた

sliding.rb

class Array
  def sliding(n)
    self.inject([]){|xs,e| xs.last.tap{|r| r.nil? ? xs << [e] : if r.length < n then r << e else xs << r.dup.tap{|_| _.shift ; _ << e } end }; xs}
  end
end

[42] pry(main)> arr = (1..10).to_a

[43] pry(main)> arr.sliding(3)
[
    [0] [
        [0] 1,
        [1] 2,
        [2] 3
    ],
    [1] [
        [0] 2,
        [1] 3,
        [2] 4
    ],
    [2] [
        [0] 3,
        [1] 4,
        [2] 5
    ],
    [3] [
        [0] 4,
        [1] 5,
        [2] 6
    ],
    [4] [
        [0] 5,
        [1] 6,
        [2] 7
    ],
    [5] [
        [0] 6,
        [1] 7,
        [2] 8
    ],
    [6] [
        [0] 7,
        [1] 8,
        [2] 9
    ],
    [7] [
        [0] 8,
        [1] 9,
        [2] 10
    ]
]