From: Robert Klemme <shortcutter@...>
Date: 2008-09-09T18:36:34+09:00
Subject: Re: Is this a sensible implementation for Array#group_by ?

2008/9/9 Max Williams <toastkid.williams@gmail.com>:
> Adam Shelley wrote
>> I think the Facets library  already has a similar method.
>
> Erik Veenstra wrote:
>> Indeed, Facets does have an Enumerable#group_by. And it has an
>> Enumerable#cluster_by as well. And the latter is the one you're
>> looking for, because you want an Array and not a Hash.
>
> Facets - investigates again... now that is *very* good indeed.  Wow.  I
> had a feeling this would exist already in a better form :)

If I would want to do it myself, then I'd probably do

module Enumerable
  def group_by
    result = Hash.new {|h,k| h[k] = []}
    each {|el| result[yield el] << el}
    result
  end
end

Kind regards

robert

-- 
use.inject do |as, often| as.you_can - without end