From: "Berger, Daniel" <Daniel.Berger@...>
Date: 2006-07-25T23:13:25+09:00
Subject: Re: Hash order bug?

> -----Original Message-----
> From: Javier Valencia [mailto:jvalencia@log01.org] 
> Sent: Tuesday, July 25, 2006 7:48 AM
> To: ruby-talk ML
> Subject: Re: Hash order bug?
> 
> 
> 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?

No, it's just the way hashes behave.  Note that there are ordered hash
implementations on the RAA:

http://raa.ruby-lang.org/project/orderedhash/

You can also use a Struct to get roughly the same effect.

Regards,

Dan


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