From: Robert Klemme <bob.news@...>
Date: 2003-10-05T02:55:22+09:00
Subject: Re: hash of hashes


"Joel VanderWerf" <vjoel@PATH.Berkeley.EDU> schrieb im Newsbeitrag
news:3F7E3AF2.2050701@path.berkeley.edu...
> Dave Brown wrote:
> > In article <200310031434.31907.argentoff@rtelekom.ru>,
> > Paul Argentoff  <argentoff@rtelekom.ru> wrote:
> > : On Friday 03 October 2003 14:04, Paul Argentoff wrote:
> > :
> > : > How can I create $Subject for future population?
> > :
> > : Let's put it this way: I need to create a nested hash which will be
populated
> > : later by referencing the keys in the subhashes. How can I do this?
> >
> > You mean, er,
> >
> > irb(main):001:0> a=Hash.new({})
> > => {}
> > irb(main):002:0> a['foo']
> > => {}
> >
> > ?
> >
> > --Dave
>
> That's like, a real bad trip, dude:
>
> irb(main):002:0> a=Hash.new({})
> => {}
> irb(main):003:0> a[1]
> => {}
> irb(main):004:0> a[1]["x"] = "y"
> => "y"
> irb(main):005:0> a
> => {}
> irb(main):006:0> a[1]
> => {"x"=>"y"}
> irb(main):007:0> a[1] = 2
> => 2
> irb(main):008:0> a[2]
> => {"x"=>"y"}
> irb(main):009:0> a[1]
> => 2
>
> It would help to do
>
> a = Hash.new {{}}
>
> since you get a new hash each time...

Not really:

irb(main):001:0> h=Hash.new{{}}
=> {}
irb(main):002:0> h[1][2]="foo"
=> "foo"
irb(main):003:0> h
=> {}
irb(main):004:0>

You need a = Hash.new {|h,k| h[k]={}} as pointed out already.

    robert


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