拆分数组子阵列基于价值 [英] Split array into sub-arrays based on value

问题描述

我一直在寻找一个阵列相当于字符串＃分裂在Ruby中的核心，并惊讶地发现，它并不存在。难道还有比以下基于值的阵列分成多个子阵列更优雅的方式？

I was looking for an Array equivalent String#split in Ruby Core, and was surprised to find that it did not exist. Is there a more elegant way than the following to split an array into sub-arrays based on a value?

class Array
  def split( split_on=nil )
    inject([[]]) do |a,v|
      a.tap{
        if block_given? ? yield(v) : v==split_on
          a << []
        else
          a.last << v
        end
      }
    end.tap{ |a| a.pop if a.last.empty? }
  end
end

p (1..9 ).to_a.split{ |i| i%3==0 },
  (1..10).to_a.split{ |i| i%3==0 }
#=> [[1, 2], [4, 5], [7, 8]]
#=> [[1, 2], [4, 5], [7, 8], [10]]

修改：对于那些有兴趣，这引发了此请求的现实世界的问题，可以在<一看到href=\"http://stackoverflow.com/questions/4798976/nokogiri-need-to-turn-markup-partitioned-by-hr-into-divs/4801341#4801341\">this回答，在这里我用@ FD的回答下面的实现。

Edit: For those interested, the "real-world" problem which sparked this request can be seen in this answer, where I've used @fd's answer below for the implementation.

推荐答案

我试着打高尔夫球了一点，仍然没有一个单一的方法，但：

I tried golfing it a bit, still not a single method though:

(1..9).chunk{|i|i%3==0}.reject{|sep,ans| sep}.map{|sep,ans| ans}

或更快：

(1..9).chunk{|i|i%3==0 || nil}.map{|sep,ans| sep&&ans}.compact

此外，可枚举＃块似乎是红宝石1.9+，但它是非常接近你想要什么。

Also, Enumerable#chunk seems to be Ruby 1.9+, but it is very close to what you want.

例如，原始输出将是：

(1..9).chunk{ |i|i%3==0 }.to_a                                       
=> [[false, [1, 2]], [true, [3]], [false, [4, 5]], [true, [6]], [false, [7, 8]], [true, [9]]]

（即 to_a 是使IRB打印一件好事，因为块给你一个枚举，而不是一个数组）

(The to_a is to make irb print something nice, since chunk gives you an enumerator rather than an Array)

修改：注意上面的优雅的解决方案比最快的实现2-3倍慢：

Edit: Note that the above elegant solutions are 2-3x slower than the fastest implementation:

module Enumerable
  def split_by
    result = [a=[]]
    each{ |o| yield(o) ? (result << a=[]) : (a << o) }
    result.pop if a.empty?
    result
  end
end

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