From: Rick DeNatale <rick.denatale@...>
Date: 2008-09-18T22:07:15+09:00
Subject: Re: Preserve insert order in a Hash

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On Thu, Sep 18, 2008 at 8:42 AM, Brian Candler <b.candler@pobox.com> wrote:

> > well, basically I just need a Hash to use String as indexes like
> >
> > sourceInfo = Hash.new
> > sourceInfo["var1"]=123
> > sourceInfo["var2"]=2
> > sourceInfo["var3"]=3
> > sourceInfo["var4"]=23
>
> What do you want to happen if sourceInfo["var2"] is assigned a second
> time? Do you want to replace it where it originally was in the sequence,
> or do you want to delete it and add the new value to the end? Or do you
> want both elements to appear at the same time? Or doesn't it matter?


FWIW, Ruby 1.9 seems to keep the original insertion order, reassiging a
value to an existing key leaves the order unchanged:

$ irb1.9
irb(main):001:0> a = {a: 1, b: 2, c: 3}
=> {:a=>1, :b=>2, :c=>3}
irb(main):002:0> a.keys
=> [:a, :b, :c]
irb(main):003:0> a[:b] = 4
=> 4
irb(main):004:0> a.keys
=> [:a, :b, :c]
irb(main):005:0> a
=> {:a=>1, :b=>4, :c=>3}
irb(main):006:0>

At least my somewhat out of date 1.9 does

$ ruby1.9 -v
ruby 1.9.0 (2008-03-21 revision 0) [i686-darwin9.2.2]

-- 
Rick DeNatale

My blog on Ruby
http://talklikeaduck.denhaven2.com/

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