in reply to Re: hash of hashes and memory space...
in thread hash of hashes and memory space...

My question came about from looking at the output of a Data::Dumper and Data::Dump of a hash of hashes I am working with. Dumping the hash only prints the first hash key/value pairs not the under lining hashes or their key/value pairs. This made me think that a hash of hashes is not one single variable (container) but that each embedded hash is it's own separate container.
  • Comment on Re^2: hash of hashes and memory space...

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Re^3: hash of hashes and memory space...
by ikegami (Patriarch) on Mar 23, 2010 at 20:16 UTC
    A "hash of hash" is really a "hash of references to hashes". 
    $h{foo}{bar} = 123;

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    is short for 
    $h{foo}->{bar} = 123;

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    and 
    ${ $h{foo} }{bar} = 123;

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    Something to try: 

    my %a;
my %b;
$a{foo} = \%b;
$a{foo}{bar} = 123;
print("$b{bar}\n");

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Re^3: hash of hashes and memory space...
by jethro (Monsignor) on Mar 24, 2010 at 01:33 UTC

    Strange. When I use Data::Dumper, I get all the subhashes shown too. Example:

    #!/usr/bin/perl
use warnings;
use strict;
use Data::Dumper;

my %hash= ( 4, {3,4,5,6,7,8});

$hash{a}{b}{c}{d}{e}=366;
print Dumper(\%hash);

#output:

$VAR1 = {
          '4' => {
                   '3' => 4,
                   '7' => 8,
                   '5' => 6
                 },
          'a' => {
                   'b' => {
                            'c' => {
                                     'd' => {
                                              'e' => 366
                                            }
                                   }
                          }
                 }
        };

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    Maybe $Data::Dumper::Maxdepth is set to 1 in your script

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      print Dumper(\%hash);

      You found my problem with Data::Dumper...

      I was using print Dumper(%hash);

      Thanks!

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