Re: Populating a nested hash with itself?

I did notice that Data::Dumper does nearly the same thing you're trying to do ... and I'm trying to figure out how to get Data::Dumper's output to "thaw" back into a usable perl variable. Perhaps someone else will answer this.

my $a = [qw{v1 v2}];
my %h = (
         k1 => {
             k11 => $a,
             k12 => 'w00t!',
         },
         k2 => {
             k21 => 'what?',
             k22 => $a,
         },
        );

use Data::Dumper;
#print Dumper(\%h);

my $h2; $h2 = {
          'k2' => {
                    'k21' => 'what?',
                    'k22' => [
                               'v1',
                               'v2'
                             ]
                  },
          'k1' => {
                    'k11' => $h2->{'k2'}{'k22'},
                    'k12' => 'w00t!'
                  }
};

print Dumper($h2);
[download]

The first hash, %h, is what you're trying to do, but in a manner that works. Then I dump it, and I pasted that output back into the code and dump the new hash-ref, $h2. But it doesn't want to work, and I'm not sure what bits of trickery are needed to get it to work - probably some Data::Dumper variables when dumping, but I'm not sure offhand.

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Re^2: Populating a nested hash with itself? by halley (Prior) on Jul 06, 2005 at 18:14 UTC
The output of Data::Dumper is not guaranteed to properly evaluate and reconstruct the data, unless you set `$Data::Dumper::Purity = 1`. It is still possible to confuse Data::Dumper in some cases, but with Purity, it'll handle most self-referential and other cyclical structures. The output with this configuration: `$VAR1 = { 'k1' => { 'k11' => [ 'v1', 'v2' ], 'k12' => 'w00t!' }, 'k2' => { 'k21' => 'what?', 'k22' => [] } }; $VAR1->{'k2'}{'k22'} = $VAR1->{'k1'}{'k11'};` [download] As you can see, Data::Dumper now produces Perl code, and not merely a Perl-like syntax to describe the data. -- `[ e d @ h a l l e y . c c ]`	[reply] [d/l] [select]

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Re^2: Populating a nested hash with itself?
by halley (Prior) on Jul 06, 2005 at 18:14 UTC

$Data::Dumper::Purity = 1

$VAR1 = {
          'k1' => {
                    'k11' => [
                               'v1',
                               'v2'
                             ],
                    'k12' => 'w00t!'
                  },
          'k2' => {
                    'k21' => 'what?',
                    'k22' => []
                  }
        };
$VAR1->{'k2'}{'k22'} = $VAR1->{'k1'}{'k11'};
[download]

Perl code

--
[ e d @ h a l l e y . c c ]

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