From: "David A. Black" <dblack@...>
Date: 2009-07-20T05:57:44+09:00
Subject: Re: removing array duplicates where a subset is unique

Hi --

On Mon, 20 Jul 2009, 7stud -- wrote:

> Chuck Remes wrote:
>
>> (And Joel, I have presorted the array prior
>> to removing the dupes so I have already taken care of the ordering
>> issue.)
>
> That's well and good, but in the process of using a hash to remove the
> duplicates, the result will be out of order.  See example below.
>
>
>>
>> I was trying to figure out how to use a hash but did not
>> make the leap to the ||= construction on my own.
>>
>
> A simple if statement will achieve the same result:
>
> a = [
>  [1, 2, 3, 10],
>  [1, 2, 3, 20],
>  [1, 2, 3, 30],
>  [2, 2, 3, 40]
> ]
>
> h = {}
>
> a.each do |suba|
>  key = suba.slice(0, 3)
>
>  if h[key]
>    next
>  else
>    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

-- 
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