Keeping a hash' sort order?

Ruby
1

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?)

how can i keep the items in the order i want?

someone said i should probly not use a hash at all? however, i do want
to keep the items organized in the order like above, but access thru
hashkeys.

hsh.each_pair{ |tag, val| …

can i use a more complex structure and sort by some internal key?

thanks!

/dc

  David "DC" Collier
  +81 (0)80 6521 9559
  skype: callto://d3ntaku
2

dc wrote:

hi -

sure this is a common question…

Yes, and that is the exact reason why I suggest you search through the
archives before posting.

how can i keep the items in the order i want?

someone said i should probly not use a hash at all? however, i do want
to keep the items organized in the order like above, but access thru
hashkeys.

hsh.each_pair{ |tag, val| …

That’s not an access by hash key but an iteration. For that nested
arrays are sufficient.

can i use a more complex structure and sort by some internal key?

As said, please go to the archives. There are numerous postings and
implementations available.

Regards

robert
3

[email protected] wrote:

gives back:
rb = RBTree.new
end
harp:~ > ruby a.rb
[“a”, 1]
[“b”, 2]
[“c”, 3]

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

Facets’ Dictionary class can handle arbitray order via #insert(i,k,v),
as well as automatic sort orders (though it is not as fast as rbtree).

T.

4

[email protected] wrote:
…

    super value
rb[ Key("c", 1) ] = 3

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



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

What’s the ‘arbitrary’ part for? The Key#<=> method is not called. The
following has the same output:

 rb = RBTree.new

 rb[ "a" ] = 1
 rb[ "b" ] = 2
 rb[ "c" ] = 3

 rb.each{|k,v| p [k,v]}
5

On Sun, 29 Oct 2006, dc wrote:

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