From: ara.t.howard@...
Date: 2006-10-29T22:34:15+09:00
Subject: Re: keeping a hash' sort order?

On Sun, 29 Oct 2006, dc wrote:

> hi -
>
> sure this is a common question...
> i have a hash of stuff that i want to load/keep in a particular order.
>
> irb(main):005:0> hsh =  { "one" => 1, "two" => 2, "three" => 3,
> "four"=>4, "twentythree"=>23 }
>
> gives back:
> => {"three"=>3, "two"=>2, "twentythree"=>23, "one"=>1, "four"=>4}
>
> ruby sorts the hash in apparent random order (by object id?)


if you really want to sort on arbitrary keys use an rbtree:

     harp:~ > cat a.rb
     require 'rbtree' # rubyforge or raa

     rb = RBTree.new

     class Key < ::String
       attr 'arbitrary'
       def initialize value, arbitrary
         super value
         @arbitrary = arbitrary
       end
       def <=> other
         self.arbitrary <=> other.arbitrary
       end
     end
     def Key(*a, &b) Key.new(*a, &b) end

     rb[ Key("a", 3) ] = 1
     rb[ Key("b", 2) ] = 2
     rb[ Key("c", 1) ] = 3

     rb.each{|k,v| p [k,v]}



     harp:~ > ruby a.rb
     ["a", 1]
     ["b", 2]
     ["c", 3]



if you want to sort on insertion order use an ordered hash:


     harp:~ > cat a.rb
     require 'alib' # rubyforge or raa
     require 'yaml'

     oh = alib.orderedhash.new

     oh['a'] = 1
     oh['b'] = 2
     oh['c'] = 3

     y oh


     harp:~ > ruby a.rb
     a: 1
     b: 2
     c: 3


more examples and explantions abound on the list if you want to google them.

-a
-- 
my religion is very simple.  my religion is kindness. -- the dalai lama