From: dblack@...
Date: 2006-07-25T22:53:10+09:00
Subject: Re: Hash order bug?

Hi --

On Tue, 25 Jul 2006, Javier Valencia wrote:

> dblack@wobblini.net wrote:
>
>> Hi --
>> 
>> On Tue, 25 Jul 2006, Javier Valencia wrote:
>> 
>>> I have this piece of simple code:
>>> 
>>> ----------------------------------------------
>>> def foo
>>>   return 5
>>> end
>>> 
>>> a = {:gr => false, :und => false, :det => true, :sta => false, :inv => 
>>> false}
>>> puts a.inspect
>>> ----------------------------------------------
>>> 
>>> when I execute it i get a totally unordered hash:
>>> 
>>> ----------------------------------------------
>>> ruby pro.rb
>>> {:inv=>false, :gr=>false, :und=>false, :det=>true, :sta=>false}
>>> ----------------------------------------------
>>> 
>>> Now, i delete the foo function from the code (the foo function don't do 
>>> nothing at all), and i get a well ordered hash:
>>> 
>>> ----------------------------------------------
>>> ruby pro.rb
>>> {:gr=>false, :und=>false, :det=>true, :sta=>false, :inv=>false}
>>> ----------------------------------------------
>>> 
>>> 
>>> 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.
>> 
>> 
>> David
>> 
>
> 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.


David

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