Re: searching nested structures

Update: It's the eval as roger implicitly pointed out in his reply as well. Time to be explicit. From man perlfunc on exists

Given an expression that specifies a hash element or array ele- ment, returns true if the specified element in the hash or array has ever been initialized, even if the corresponding value is undefined. The element is not autovivified if it doesn't exist.

You are autovifying.

You can see this by modifying your code as such.. (use Data::Dumper)

.
.
.
            print "----\n";
            print Dumper $data;
            my $ref = qq|\$data->{$k}$path|;
            print "String: $ref\n";
            if (my $val = eval($ref)) {
                push @results, ref($val) ? $val : eval "\\$ref";
            }

            if (exists $data->{$k}) {
                print Dumper $data;
                push @results, rec_data($path, $data->{$k});
.
.
.
[download]

Your eval is creating the a-formentioned structure. You may wanna break down your search structure in a different way.

Here's the output from above. You are creating a circular reference.

$VAR1 = {
          'foo' => {
                     'baz' => 'baz',
                     'bar' => 'bar'
                   },
          'bar' => {
                     'baz' => 'baz'
                   }
        };
String: $data->{foo}->{foo}->{bar}
$VAR1 = {
          'foo' => {
                     'foo' => {},
                     'baz' => 'baz',
                     'bar' => 'bar'
                   },
          'bar' => {
                     'baz' => 'baz'
                   }
        };
[download]

Play that funky music white boy..

Comment on Re: searching nested structures Select or Download Code

Replies are listed 'Best First'.
Re: Re: searching nested structures by pg (Canon) on Jan 05, 2004 at 05:05 UTC
add on top of what sporty quoted, exists() is just one case for autovivification. To be precise on autovivification: any attempt to read or test an element that does not exist, will create its ancestors. `use Data::Dumper; use strict; use warnings; my $data = {"a" => 1}; $data->{"b"}->{"b"}->{"b"}->{"b"};#useless use of hash element in void + context? interesting error message. The useless use is actually not +that useless. print Dumper($data);` [download] this prints: `$VAR1 = { 'a' => 1, 'b' => { 'b' => { 'b' => {} } } };` [download]	[reply] [d/l] [select]

Replies are listed 'Best First'.

Re: Re: searching nested structures
by pg (Canon) on Jan 05, 2004 at 05:05 UTC

add on top of what sporty quoted, exists() is just one case for autovivification. To be precise on autovivification: any attempt to read or test an element that does not exist, will create its ancestors.

use Data::Dumper;
use strict;
use warnings;

my $data = {"a" => 1};
$data->{"b"}->{"b"}->{"b"}->{"b"};#useless use of hash element in void
+ context? interesting error message. The useless use is actually not 
+that useless.
print Dumper($data);
[download]

this prints:

$VAR1 = {
          'a' => 1,
          'b' => {
                   'b' => {
                            'b' => {}
                          }
                 }
        };
[download]

[reply]
[d/l]
[select]