From: Alex Young <alex@...>
Date: 2006-07-26T05:12:43+09:00
Subject: Re: Hash order bug?

Kero wrote:
> [snip]
>>>>> What's happening? all my code is behaving wrong because of that.
>>>> Hashes are unordered.  If you need an ordered collection, you'll need
>>>> to use an array.
>>> Oh my god, i didn't know it, sorry. Is that a missing feature?
>> Debate rages on this point :-)  It's mostly a speed issue, I think.
>> At least my memory is that Matz's latest statement was to the effect
>> that he would do it if it could be done efficiently.
>>
>> The question came up during a lunch here at OSCON (with me, Jim
>> Weirich, Pat Eyler, and a fellow named Nicolas whose last name I'm
>> afraid I don't remember) as to whether making hashes ordered in a
>> future Ruby would break any existing code.  I think the answer is no,
>> which is kind of interesting considering what a major change it would
>> be.  It's a case where the feature would be purely additive.
> 
> I guess there won't be many ppl using algorithms that use the *un*sorted
> aspect of a Hash. 
It's not that it's unordered, it's that it's anordered.  The concept 
doesn't apply.  It's a bucket, not a queue.  There are many, many 
applications that don't care about entry order.

>Using Kernel#rand instead of Object#hash seems
> better. printing a few hash-values suggest they're not that random anyway...
The order is unpredictable and implementation dependent.

-- 
Alex