8 lines
		
	
	
		
			160 B
		
	
	
	
		
			Ruby
		
	
	
	
	
	
		
		
			
		
	
	
			8 lines
		
	
	
		
			160 B
		
	
	
	
		
			Ruby
		
	
	
	
	
	
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								module Enumerable
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								  def group_by
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								    inject({}) do |h, e|
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								      h.fetch(yield(e)) { |k| h[k] = [] } << e; h
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								    end
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								  end unless method_defined?(:group_by)
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								end
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