Forum: Ruby how to make a[2][2][3]=4 work?

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gpy g. (Guest)
on 2007-06-12 10:29
a=Hash.new{|h,k|
  h[k]={}
}

p a[1]=1

a[2][1]=2
 #a[2][2][3]=4
p a
gpy g. (Guest)
on 2007-06-12 10:35
I know this can work,but I think it is suck
a=Hash.new{|h,k|
  h[k]=Hash.new{|h,k|h[k]=Hash.new{|h,k|h[k]={}}}
}

p a[1]=1

a[2][1]=2
a[2][2][3]=4
a[3][1][1][1]=1
p a
Daniel S. (Guest)
on 2007-06-12 10:42
(Received via mailing list)
> p a
build_hash = proc {|h,k|h[k] = Hash.new &build_hash }
a = Hash.new &build_hash
Sylvain J. (Guest)
on 2007-06-12 10:50
(Received via mailing list)
def recursive_hash
  Hash.new { |h, k| h[k] = recursive_hash }
end
a = recursive_hash

Or even

class Hash
  def self.recursive
    new { |h, k| h[k] = recursive }
  end
end

which gives

>> a = Hash.recursive
=>
>> a[1][2][3][4] = 1
=> 1
>> puts a.inspect
{1=>{2=>{3=>{4=>1}}}}
Daniel M. (Guest)
on 2007-06-12 16:23
(Received via mailing list)
In addition to what's already been posted, there's this, which doesn't
require any extra variables or methods:

a = Hash.new{|h,k| h[k]=Hash.new &h.default_proc}

gz zz <removed_email_address@domain.invalid> writes:

> a[2][1]=2
> a[2][2][3]=4
> a[3][1][1][1]=1
> p a

irb(main):001:0> a = Hash.new{|h,k| h[k]=Hash.new &h.default_proc}
=> {}
irb(main):002:0> a[2][1]=2
=> 2
irb(main):003:0> a[2][2][3]=4
=> 4
irb(main):004:0> a[3][1][1][1]=1
=> 1
irb(main):005:0> p a
{2=>{1=>2, 2=>{3=>4}}, 3=>{1=>{1=>{1=>1}}}}
=> nil
Jenda K. (Guest)
on 2007-06-12 16:50
gz zz wrote:
> a=Hash.new{|h,k|
>   h[k]={}
> }
>
> p a[1]=1
>
> a[2][1]=2
>  #a[2][2][3]=4
> p a

Sure. Use Perl.

Oops, sorry. I forgot, datastructure autovivification is wrong,
variables springing into life (or maybe not, read the rest of the method
to find out) inadvertently are good.

Jenda
Martin DeMello (Guest)
on 2007-06-12 17:25
(Received via mailing list)
On 6/12/07, Jenda K. <removed_email_address@domain.invalid> wrote:
>
> Sure. Use Perl.
>
> Oops, sorry. I forgot, datastructure autovivification is wrong,
> variables springing into life (or maybe not, read the rest of the method
> to find out) inadvertently are good.

That's okay, it happens to the best of us.

martin
Gavin K. (Guest)
on 2007-06-12 19:56
(Received via mailing list)
On Jun 12, 6:21 am, Daniel M. <removed_email_address@domain.invalid> wrote:
> In addition to what's already been posted, there's this, which doesn't
> require any extra variables or methods:
>
> a = Hash.new{|h,k| h[k]=Hash.new &h.default_proc}

Thanks for this - I didn't know about the default_proc method. Quite
elegant in this case.
Fsormok F. (Guest)
on 2007-07-20 21:57
> Sure. Use Perl.

What's the ruby-way of such things?

e.g.:

   int[eth0][ip]   = "10.0.0.1"
   int[eth0][mask] = "255.255.255.0"
   int[eth0][cidr] = "24"
   int[eth1][ip]   = "10.0.1.1"
   int[eth1][mask] = "255.255.255.0"
   int[eth1][cidr] = "24"
   .
   .
   .

I like it if I have all these informations handy within one hash. But
even for me as a realy ruby-newby this looks much more like perl than
ruby.

It would be great to hear your thoughts how this would be done "the ruby
way"...

clean and elegant :-)

--fsormok
Bill K. (Guest)
on 2007-07-20 23:49
(Received via mailing list)
From: "Fsormok F." <removed_email_address@domain.invalid>
>   int[eth1][ip]   = "10.0.1.1"
> It would be great to hear your thoughts how this would be done "the ruby
> way"...
>
> clean and elegant :-)

You can do that in Ruby, if you want to.
See: http://blade.nagaokaut.ac.jp/cgi-bin/scat.rb/ruby/...

irb(main):011:0> int = Hash.new{|h,k| h[k]=Hash.new &h.default_proc}
=> {}
irb(main):012:0> int[:eth0][:ip]   = "10.0.0.1"
irb(main):013:0> int[:eth0][:mask] = "255.255.255.0"
irb(main):014:0> int[:eth0][:cidr] = "24"
irb(main):015:0> int[:eth1][:ip]   = "10.0.1.1"
irb(main):016:0> int[:eth1][:mask] = "255.255.255.0"
irb(main):017:0> int[:eth1][:cidr] = "24"
irb(main):018:0> int
=> {:eth0=>{:ip=>"10.0.0.1", :mask=>"255.255.255.0", :cidr=>"24"},
:eth1=>{:ip=>"10.0.1.1", :mask=>"255.255.255.0", :cidr=>"24"}}


Another possibility might be OpenStruct.

irb(main):026:0> require 'ostruct'
=> true
irb(main):027:0> int = Hash.new{|h,k| h[k]=OpenStruct.new}
=> {}
irb(main):028:0> int[:eth0].ip   = "10.0.0.1"
irb(main):029:0> int[:eth0].mask = "255.255.255.0"
irb(main):030:0> int[:eth0].cidr = "24"
irb(main):031:0> int[:eth1].ip   = "10.0.1.1"
irb(main):032:0> int[:eth1].mask = "255.255.255.0"
irb(main):033:0> int[:eth1].cidr = "24"
irb(main):034:0> int
=> {:eth0=>#<OpenStruct ip="10.0.0.1", mask="255.255.255.0", cidr="24">,
:eth1=>#<OpenStruct ip="10.0.1.1", mask="255.255.255.0",
cidr="24">}


Regards,

Bill
William J. (Guest)
on 2007-07-21 00:26
(Received via mailing list)
On Jun 12, 1:29 am, gz zz <removed_email_address@domain.invalid> wrote:
> a=Hash.new{|h,k|
>   h[k]={}
>
> }
>
> p a[1]=1
>
> a[2][1]=2
>  #a[2][2][3]=4


a = {}
    ==>{}
a[1] = 1
    ==>1
a[ [2,1] ] = 2
    ==>2
a[ [2,2,3] ] = 4
    ==>4
p a
{[2, 2, 3]=>4, [2, 1]=>2, 1=>1}
    ==>nil
Fsormok F. (Guest)
on 2007-07-23 11:15
> a = Hash.new{|h,k| h[k]=Hash.new &h.default_proc}

> irb(main):026:0> require 'ostruct'
> irb(main):027:0> int = Hash.new{|h,k| h[k]=OpenStruct.new}

>a = {}
>    ==>{}
>a[1] = 1
>    ==>1
>a[ [2,1] ] = 2
>    ==>2
>a[ [2,2,3] ] = 4
>    ==>4
>p a
>{[2, 2, 3]=>4, [2, 1]=>2, 1=>1}
>    ==>nil

Tanks for the replies.

I'm just a little bit confused because in ruby everything is lean and
clean but when it comes to hashes of hashes it gets kind of complicated.
For me it looks like ruby has another "concept" of solving such things.

-fsormok
Robert D. (Guest)
on 2007-07-26 02:45
(Received via mailing list)
On 7/23/07, Fsormok F. <removed_email_address@domain.invalid> wrote:
> >    ==>2
> For me it looks like ruby has another "concept" of solving such things.
>

Hmm the context of this statement seems not complete in *this* thread,
maybe you could elaborate on this a little bit?
Personally I feel that Ruby's concept of Hashes is clearcut and
exactly the same as in most of its relatives (Perl,Python...).

What exactly would you like to have "simpler"?

Cheers
Robert
Mark T. (Guest)
on 2007-07-26 02:45
(Received via mailing list)
On Jul 20, 1:57 pm, Fsormok F. <removed_email_address@domain.invalid> wrote:
>    int[eth1][mask] = "255.255.255.0"
> way"...
>
> clean and elegant :-)

In my personal opinion, multilevel hashes aren't clean and elegant in
any language. I'd try to make an object out of it:

class Interface
  attr_accessor :name, :ip, :mask, :cidr
end

i = Interface.new
i.name = "eth0"
i.ip = "10.0.0.1"
i.mask = "255.255.255.0"
i.cidr = 24

- Mark.
Fsormok F. (Guest)
on 2007-07-31 13:41
Thanx Mark

This is exactly what i liked to hear :-)

> In my personal opinion, multilevel hashes aren't clean and elegant in
> any language.

HoH are quiet common in perl (at least I use them alot), not in Ruby
IMHO.

But as always: TMTOWTDI

> I'd try to make an object out of it:
>
> class Interface
>   attr_accessor :name, :ip, :mask, :cidr
> end
>
> i = Interface.new
> i.name = "eth0"
> i.ip = "10.0.0.1"
> i.mask = "255.255.255.0"
> i.cidr = 24
>
> - Mark.
Robert K. (Guest)
on 2007-07-31 13:47
(Received via mailing list)
2007/7/23, Fsormok F. <removed_email_address@domain.invalid>:
> >    ==>2
> For me it looks like ruby has another "concept" of solving such things.
Its this what you are looking for?

$ ruby <<XXX
> miss = lambda {|h,k| h[k] = Hash.new(&miss)}
> hash = Hash.new(&miss)
> hash[1][2]=3
> hash[4]=5
> p hash
> XXX
{1=>{2=>3}, 4=>5}

Kind regards

robert
Gabe D. (Guest)
on 2009-04-02 20:25
Daniel M. wrote:
> In addition to what's already been posted, there's this, which doesn't
> require any extra variables or methods:
>
> a = Hash.new{|h,k| h[k]=Hash.new &h.default_proc}

That's clever, but I think the way it automatically creates keys is
wrong.  You need to be able to check to see if a key exists without
polluting the hash with a bunch of empties.

Hence my new gem:

http://github.com/dasil003/safe-nested-hash
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