From: Siep Korteling <s.korteling@...>
Date: 2009-07-20T07:07:22+09:00
Subject: Re: removing array duplicates where a subset is unique

David A. Black wrote:
> Hi --
> 
> On Mon, 20 Jul 2009, 7stud -- wrote:
> 
>>>
>>  [2, 2, 3, 40]
>>    h[key] = suba
>>  end
>>
>> end
>>
>> p h.values
>>
>> --output:--
>> [[2, 2, 3, 40], [1, 2, 3, 10]]
> 
> I'm not sure what that buys you, though. The ||= idiom should work
> fine, unless you need to do something extra during the if statement.
> 
> 
> David

Facets has enumerable#uniq_by implemented like this:

def uniq_by #:yield:
    h = {}; inject([]) {|a,x| h[yield(x)] ||= a << x}
end

So you can do:

  require 'facets'
  a = [[1, 2, 3, 4, 5], [1, 2, 3, 9, 4], [1, 2, 3, 4, 4]]
  res = a.uniq_by{|el| el[0..2]}

Don't know about performance.

hth,

Siep

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