Ordered Hash (v. 1.8)

Ruby
1

I am running Ruby v. 1.8.7 and I have installed the orderedhash gem. I
know that the purpose of orderedhash is to preserve the order of
creation. However, what I’d really like to do is, after the hash has
been created, sort it on the key in a manner similar to the way that I
would sort an array with the sort!() method and then preserve the sorted
order. Any ideas on how I might accomplish that feat? Thanks for any
input.

 ... doug
2

Am 30.11.2012 02:46, schrieb Doug J.:

I am running Ruby v. 1.8.7 and I have installed the orderedhash gem. I
know that the purpose of orderedhash is to preserve the order of
creation. However, what I’d really like to do is, after the hash has
been created, sort it on the key in a manner similar to the way that I
would sort an array with the sort!() method and then preserve the sorted
order. Any ideas on how I might accomplish that feat? Thanks for any
input.

  ... doug

  1. You could use the RBTree gem.

  2. Iterate through the sorted keys when you need to access elements
    in sorted order:

1.9.3p194 :001 > hash = {:c => 1, :a => 2, :b => 3}
=> {:c=>1, :a=>2, :b=>3}
1.9.3p194 :002 > sorted_keys = hash.keys.sort
=> [:a, :b, :c]
1.9.3p194 :003 > sorted_keys.each do |key|
1.9.3p194 :004 > puts “#{key} => #{hash[key]}”
1.9.3p194 :005?> end
a => 2
b => 3
c => 1
=> [:a, :b, :c]

3

creation. However, what I’d really like to do is, after the hash has
been created, sort it on the key in a manner similar to the way that I
would sort an array with the sort!() method and then preserve the sorted
order. Any ideas on how I might accomplish that feat? Thanks for any
input.

 ... doug

Does this work?

h = {}
arr = [“t”,“c”,“h”,“b”,“l”]
arr.each{|x| h[x] = x + “ook”}

h = Hash[h.sort]
p h #> {“b”=>“book”, “c”=>“cook”, “h”=>“hook”, “l”=>“look”,
“t”=>“took”}

Harry

4

Am 30.11.2012 07:15, schrieb [email protected]:

1.9.3p194 :004 > puts “#{key} => #{hash[key]}”
1.9.3p194 :005?> end
a => 2
b => 3
c => 1
=> [:a, :b, :c]

correction: in 1.8, when your keys are symbols you need to sort with

sorted_keys = hash.keys.sort_by(&:to_s)

5

Am 30.11.2012 07:19, schrieb Harry K.:

h = {}
arr = [“t”,“c”,“h”,“b”,“l”]
arr.each{|x| h[x] = x + “ook”}

h = Hash[h.sort]
p h #> {“b”=>“book”, “c”=>“cook”, “h”=>“hook”, “l”=>“look”, “t”=>“took”}

not in Ruby 1.8!

And in 1.9 you would have to recreate the complete hash for
each key-value pair that is added.

6

Am 30.11.2012 07:22, schrieb [email protected]:

  ... doug

You can access the elements in sorted order even more easily like this:

hash = {:c => 1, :a => 2, :b => 3}

hash.sort_by(&:to_s).each do |k, v|
puts “#{k} => #{v}”
end

output:

a => 2
b => 3
c => 1

7

I am running Ruby v. 1.8.7 and I have installed the orderedhash gem. I
know that the purpose of orderedhash is to preserve the order of
creation. However, what I’d really like to do is, after the hash has
been created, sort it on the key in a manner similar to the way that I
would sort an array with the sort!() method and then preserve the sorted
order. Any ideas on how I might accomplish that feat? Thanks for any
input.

 ... doug

If you want to also keep the original order, maybe this is worth a

look.

I’m using 1.9 so I can’t test it for your setup.

class Hash
def myway
Hash[*sort.flatten] #Ruby 1.8 ?
#Hash[sort] # Ruby1.9
end
end

h = {}
arr = [“t”,“c”,“h”,“b”,“l”]
arr.each{|x| h[x] = x + “ook”}

p h #> {“t”=>“took”, “c”=>“cook”, “h”=>“hook”,
“b”=>“book”, “l”=>“look”}
p h.myway #> {“b”=>“book”, “c”=>“cook”, “h”=>“hook”, “l”=>“look”,
“t”=>“took”}

Harry

8

Am 30.11.2012 08:09, schrieb Harry K.:

If you want to also keep the original order, maybe this is worth a look.

I’m using 1.9 so I can’t test it for your setup.

class Hash
def myway
Hash[*sort.flatten] #Ruby 1.8 ?
#Hash[sort] # Ruby1.9
end
end

This does not work in 1.8, because hashes in 1.8 do
not keep the insertion order.

9

On Fri, Nov 30, 2012 at 3:34 PM, [email protected] wrote:

end
end

This does not work in 1.8, because hashes in 1.8 do
not keep the insertion order.

That’s why Doug had installed the OrderedHash Gem I guess. So with a
little change that should work:

untested:

OrderedHash[*sort.flatten]

Kind regards

robert

10

Thanks to all who contributed in this thread. Using your valuable
contributions, I was able to solve my problem. The final solution was
not at all what I had in mind when I posted my original post. Thanks to
the guidance obtained from this thread, I was able to accomplish my
objective by using the sort method of a traditional hash (i.e., I did
not need the ordered hash as I thought that I would). Thanks for
getting me pointed in the right direction.

  ... doug
11

On Thursday, November 29, 2012 8:46:48 PM UTC-5, Doug J. wrote:

I am running Ruby v. 1.8.7 and I have installed the orderedhash gem. I
know that the purpose of orderedhash is to preserve the order of
creation. However, what I’d really like to do is, after the hash has
been created, sort it on the key in a manner similar to the way that I
would sort an array with the sort!() method and then preserve the sorted
order. Any ideas on how I might accomplish that feat? Thanks for any
input.

You can use Hashery’s Disctionary class.

$ gem install hashery

Then code:

require ‘hashery/dictionary’

dict = Hashery::Dictionary.new_by{ |k,v| k }