Multiple level hash assignment equivalence to perl

ruby-talk
1

Is there a succinct way in ruby to do a multiple level hash assignement?
I am more
used to perl, which you can do something like

$hp->{level1}->{level2} = 3

even if the first and second level had never existed below.

Any help would be appreciated.

Regards,
Don Mc

···

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Posted via http://www.ruby-forum.com/.

2

don mc wrote:

Is there a succinct way in ruby to do a multiple level hash assignement? I am more
used to perl, which you can do something like

$hp->{level1}->{level2} = 3

even if the first and second level had never existed below.

There's an autovivification trick, using the default proc of a hash (see ri default_proc):

irb(main):002:0> pr = proc {|h,k| h[k]=Hash.new(&pr) }
=> #<Proc:0x02c15618@(irb):2>
irb(main):003:0> h = Hash.new(&pr)
=> {}
irb(main):004:0> h[1][2][3][4] = 5
=> 5
irb(main):005:0> h
=> {1=>{2=>{3=>{4=>5}}}}

···

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        vjoel : Joel VanderWerf : path berkeley edu : 510 665 3407

3

Thanks! Thats just what I needed.

Regards,
Don

Joel VanderWerf wrote:

···

don mc wrote:

Is there a succinct way in ruby to do a multiple level hash assignement?
I am more
used to perl, which you can do something like

$hp->{level1}->{level2} = 3

even if the first and second level had never existed below.

There's an autovivification trick, using the default proc of a hash (see
ri default_proc):

irb(main):002:0> pr = proc {|h,k| h[k]=Hash.new(&pr) }
=> #<Proc:0x02c15618@(irb):2>
irb(main):003:0> h = Hash.new(&pr)
=> {}
irb(main):004:0> h[1][2][3][4] = 5
=> 5
irb(main):005:0> h
=> {1=>{2=>{3=>{4=>5}}}}

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Posted via http://www.ruby-forum.com/\.

4

^^
                                  ^^

nice! my approach is slightly more verbose.

-a

···

On Thu, 13 Jul 2006, Joel VanderWerf wrote:

don mc wrote:

Is there a succinct way in ruby to do a multiple level hash assignement? I am more
used to perl, which you can do something like

$hp->{level1}->{level2} = 3

even if the first and second level had never existed below.

There's an autovivification trick, using the default proc of a hash (see ri default_proc):

irb(main):002:0> pr = proc {|h,k| h[k]=Hash.new(&pr) }
=> #<Proc:0x02c15618@(irb):2>
irb(main):003:0> h = Hash.new(&pr)

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