Hi,
I would like to know if it's possible to insert values in a Hash and
then extract all of them in the same insertion order.

I noticed that if I then try to print the content of an Hash using
"each" the order is not the same as the insertion.

Thanks

Peña, Botp wrote:
> From: Me Me [mailto:emanuelef@tiscali.it]
> # I would like to know if it's possible to insert values in a Hash and
> # then extract all of them in the same insertion order.
>
> only in ruby 1.9

Could anybody explain why this feature was added? Isn't it going to slow
down the operations on the Hash? I think it is useless to mix Array with
Hash.

TPR.

Thomas B. wrote:
> Peña, Botp wrote:
>> From: Me Me [mailto:emanuelef@tiscali.it]
>> # I would like to know if it's possible to insert values in a Hash and
>> # then extract all of them in the same insertion order.
>>
>> only in ruby 1.9
>
> Could anybody explain why this feature was added? Isn't it going to slow
> down the operations on the Hash? I think it is useless to mix Array with
> Hash.
>
> TPR.

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

and then print them in the exact order of insertion

Dick Davies wrote:
> On Thu, Sep 18, 2008 at 11:13 AM, Me Me <emanuelef@tiscali.it> wrote:
>>> Hash.
>>
>> and then print them in the exact order of insertion
>
> Can't you just sort them on the way out?
> i.e.
>
> sourceinfo.keys.sort.each { |k|
>   sourceinfo[k].do_stuff
> }

thanks
well in this case they will be sorted alphabetically, right?
the example is simplyfied, in my case the keys have differernt names.

unknown wrote:
> a  = []
> a.push 1
> a.push 2
> a.push 3
> a.each {|e|puts e}

I think this is not my case, I need a Hash as I explained

> 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?

I am just wondering because perhaps all you need is

sourceInfo = []
sourceInfo << ["var1",123]
sourceInfo << ["var2",2]
sourceInfo << ["var3",3]
sourceInfo << ["var4",4]
sourceInfo.each { |k,v| puts "#{k}=>#{v}" }

At least, that's fine if all you want to do is iterate over the
collection and add new elements. Finding or deleting elements by key
requires a linear search:

dummy,value = sourceInfo.find { |k,v| k == "var2" }

However you can optimise this by building a hash as you go which points
to the same elements; or you could build an array containing just the
keys.

  class HashAndArray
    def initialize
      @h, @a = {}, []
    end
    def [](k)
      @h[k]
    end
    def []=(k,v)
      @a << k unless @h.has_key?(k)
      @h[k] = v
    end
    def each
      @a.each { |k| yield k,@h[k] }
    end
  end

  sourceInfo = HashAndArray.new
  sourceInfo["var1"]=123
  sourceInfo["var2"]=2
  sourceInfo["var3"]=3
  sourceInfo["var4"]=23
  sourceInfo.each { |k,v| puts "#{k}=>#{v}" }
  puts sourceInfo["var2"]

Adding a delete() method is left as an exercise.

On Thu, Sep 18, 2008 at 6:28 AM, Yukihiro Matsumoto
<matz@ruby-lang.org>wrote:

> |Isn't it going to slow down the operations on the Hash?
>
> No. hash reference operation does not touch order information, only
> for iteration.  Memory consumption increased a bit.
>

If I remember correctly, it's been a while since I looked at the code,
1.9
implements this by using a singly linked list which introduces a small
overhead only when elements are either added or deleted.

--
Rick DeNatale

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

Hi,

Yukihiro Matsumoto wrote in [ruby-talk:315237]:
At Thu, 18 Sep 2008 19:28:28 +0900,
> |Could anybody explain why this feature was added?
>
> Useful for some cases, especially for keyword arguments.

And the performance of iterations improved a little, but
significantly.

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

> 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/

Bill Kelly wrote:
> From: "Me Me" <emanuelef@tiscali.it>
>>
>> I think this is not my case, I need a Hash as I explained
>
> Here's an implementation for ruby 1.8 ... I apologize for the lack of
> tests.
>

Thanks a lot! That worked perfectly
Bye

On Sep 18, 2008, at 3:42 AM, Me Me wrote:

>
gem install orderedhash

a @ http://codeforpeople.com/

On Sep 18, 2008, at 10:01 AM, jim finucane wrote:

> a
cfp:~ > cat a.rb
require 'rubygems'
require 'rbtree'


# rbtree is sorted by the keys 'natural' sort order
# *not* the insertion order

rb = RBTree.new

rb['z'] = 3
rb['y'] = 2
rb['x'] = 1

rb.each do |key, value|
   puts "#{ key } : #{ value }"
end



cfp:~ > ruby a.rb
x : 1
y : 2
z : 3


a @ http://codeforpeople.com/

Peña, Botp wrote:
> From: Me Me [mailto:emanuelef@tiscali.it]
> # I would like to know if it's possible to insert values in a Hash and
> # then extract all of them in the same insertion order.
>
> only in ruby 1.9

Well, that is not *entirely* true.

h={}
p h
h[1]=1
p h
h[2]=1
p h
h[3]=1
p h
h
p h
h[1.5]=1
p h
h
p h
h[0]=1
p h
h
p h

yields:

{}
{1=>1}
{1=>1, 2=>1}
{1=>1, 2=>1, 3=>1}
{1=>1, 2=>1, 3=>1}
{1=>1, 2=>1, 3=>1, 1.5=>1}
{1=>1, 2=>1, 3=>1, 1.5=>1}
{1=>1, 2=>1, 3=>1, 1.5=>1, 0=>1}
{1=>1, 2=>1, 3=>1, 1.5=>1, 0=>1}


in JRUBY 1.1 which I am running on windows under netbeans.