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PORuby inject with index and brackets
 

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    <p>I try to clean my Code. The first Version uses <code>each_with_index</code>. In the second version I tried to compact the code with the <code>Enumerable.inject_with_index-construct</code>, that I found <a href="http://www.ruby-forum.com/topic/934794">here</a>.</p> <p>It works now, but seems to me as obscure as the first code. Add even worse I don't understand the brackets around element,index in</p> <pre><code>.. .inject(groups) do |group_container, (element,index)| </code></pre> <p>but they are necessary</p> <ul> <li>What is the use of these brackets?</li> <li>How can I make the code clear and readable?</li> </ul> <h2>FIRST VERSION -- WITH "each_with_index"</h2> <pre><code>class Array # splits as good as possible to groups of same size # elements are sorted. I.e. low elements go to the first group, # and high elements to the last group # # the default for number_of_groups is 4 # because the intended use case is # splitting statistic data in 4 quartiles # # a = [1, 8, 7, 5, 4, 2, 3, 8] # a.sorted_in_groups(3) # =&gt; [[1, 2, 3], [4, 5, 7], [8, 8]] # # b = [[7, 8, 9], [4, 5, 7], [2, 8]] # b.sorted_in_groups(2) {|sub_ary| sub_ary.sum } # =&gt; [ [[2, 8], [4, 5, 7]], [[7, 8, 9]] ] def sorted_in_groups(number_of_groups = 4) groups = Array.new(number_of_groups) { Array.new } return groups if size == 0 average_group_size = size.to_f / number_of_groups.to_f sorted = block_given? ? self.sort_by {|element| yield(element)} : self.sort sorted.each_with_index do |element, index| group_number = (index.to_f / average_group_size).floor groups[group_number] &lt;&lt; element end groups end end </code></pre> <h2>SECOND VERSION -- WITH "inject" AND index</h2> <pre><code>class Array def sorted_in_groups(number_of_groups = 4) groups = Array.new(number_of_groups) { Array.new } return groups if size == 0 average_group_size = size.to_f / number_of_groups.to_f sorted = block_given? ? self.sort_by {|element| yield(element)} : self.sort sorted.each_with_index.inject(groups) do |group_container, (element,index)| group_number = (index.to_f / average_group_size).floor group_container[group_number] &lt;&lt; element group_container end end end </code></pre>
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