symbolic references

[David Byrne]

Greetings,
I’m trying to generate a tree of nested hashes [of an
arbitrary size].
Perhaps you could suggest a better solution.
Currently I'm trying to use symbolic references
according to the literature… but without much luck.

Best regards,
David

My script is as follows (for now, I’ve tried to keep
the tree as simple as possible):

#!perl

#use strict;
# Currently commented-out because of warning: "Can't
use string ("1") as a SCALAR ref".

use warnings;
use Data::Dumper;

my ($href, %Tree, $cluster_id, $split_val, $num_child,
$i, $j, $k);
$href = \%Tree;

$cluster_id = 698;
$split_val = 1;
$num_child = 2;
# For now, the above values are arbitrary
place-holders.

$i = 0;
$j = 1;
while ($i<4) {
$$i = {
ClusterNum => $cluster_id,
SplitValue => $split_val,
NumChildren=> $num_child,
Child => $$j,
# ‘Child’ value should be a reference to the
subsequent hash.
};
if ($i==0) {
$Tree{Root} = \$$i;
next;
}
$k = ($i - 1);
$$k = \$$i;
$i = ($i + 2);
$j = ($j + 2);
}

print Dumper($href)."\n";

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[James Edward Gray II]

On Feb 4, 2004, at 1:38 PM, David Byrne wrote:

> Greetings,

Hello.

> I’m trying to generate a tree of nested hashes [of an
> arbitrary size].

I'm trying to run the code you posted, so I can see what the heck is
going on. That's not going well for me either. <laughs> My processor
usage spikes through the roof, but it doesn't seem to get anywhere.
Does this run for you?

> Perhaps you could suggest a better solution.

Perhaps. I know you're building some sort of hash tree, but I have no
idea why. Can you tell us what you're aiming for?

> Currently I'm trying to use symbolic references according to the
> literature but without much luck.

My opinion is that we can do better than symbolic references, yes.
Unfortunately, I don't understand what we're trying to do. Take a step
back and explain the problem to us, if you would, not the problem with
the implementation.

James

[David Byrne]

Okay, sorry to be somewhat unclear with my question.
Here’s some sample input data that may help to clear
things up:

#######################
node_id = 0
parent_node_id = N/A
child_node_ids = 1, 2

node_id = 1
parent_node_id = 0
child_node_ids = 3, 4

node_id = 2
parent_node_id = 0
child_node_ids = 5, 6, 7

node_id = 3
parent_node_id = 1
child_node_ids = N/A

node_id = 4
parent_node_id = 1
child_node_ids = 8, 9

node_id = 5
parent_node_id = 2
child_node_ids = N/A

node_id = 6
parent_node_id = 2
child_node_ids = 10

node_id = 7
parent_node_id = 2
child_node_ids = N/A

node_id = 8
parent_node_id = 4
child_node_ids = N/A

node_id = 9
parent_node_id = 4
child_node_ids = 11, 12

#####...and so on #####

Notes:
- node_id = 0 is the root node.
- N/A means no further relationships exist.
- Only one parent exists for each child.
- The 'child_node_id' is redundant data. There will
be similar descriptive data for each node, but it
isn’t important for the structure of the tree.

Question: How can I create a tree (i.e. a hash of
hashes) given the above relationships?


--- James Edward Gray II <james@grayproductions.net>
wrote:

> On Feb 4, 2004, at 1:38 PM, David Byrne wrote:
>

> > Greetings,

>
> Hello.
>

> > I’m trying to generate a tree of nested hashes [of

> an

> > arbitrary size].

>
> I'm trying to run the code you posted, so I can see
> what the heck is
> going on. That's not going well for me either.
> <laughs> My processor
> usage spikes through the roof, but it doesn't seem
> to get anywhere.
> Does this run for you?
>

> > Perhaps you could suggest a better solution.

>
> Perhaps. I know you're building some sort of hash
> tree, but I have no
> idea why. Can you tell us what you're aiming for?
>

> > Currently I'm trying to use symbolic references

> according to the

> > literature but without much luck.

>
> My opinion is that we can do better than symbolic
> references, yes.
> Unfortunately, I don't understand what we're trying
> to do. Take a step
> back and explain the problem to us, if you would,
> not the problem with
> the implementation.
>
> James
>
>
> --
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> For additional commands, e-mail:
> [email]beginners-help@perl.org[/email]
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>
>

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[James Edward Gray II]

On Feb 4, 2004, at 4:19 PM, David Byrne wrote:

> Okay, sorry to be somewhat unclear with my question.
> Here’s some sample input data that may help to clear
> things up:

See if this gets you going. It's one possible answer.

James

#!/usr/bin/perl

use strict;
use warnings;

use Data::Dumper;

my $tree = data_to_hash_tree(); # build tree

print Dumper($tree); # print tree

sub data_to_hash_tree {
my @nodes; # to store nodes during reading

local $/ = ''; # use "paragraph" read mode

while (<DATA>) {
my %node = map { split /\s*=\s*/ } split /\n/; # build node from data
$nodes[$node{node_id}] = \%node; # add to list
}

foreach (@nodes) { # cross reference and clean up nodes
if ($_->{child_node_ids} eq 'N/A') { $_->{child_node_ids} = [ ]; }
else {
$_->{child_node_ids} =
[ map { $nodes[$_] } split /,\s*/, $_->{child_node_ids} ];
}

$_->{parent_node_id} = undef if $_->{parent_node_id} eq 'N/A';

}

return $nodes[0]; # return root
}

__DATA__
node_id = 0
parent_node_id = N/A
child_node_ids = 1, 2

node_id = 1
parent_node_id = 0
child_node_ids = 3, 4

node_id = 2
parent_node_id = 0
child_node_ids = 5, 6, 7

node_id = 3
parent_node_id = 1
child_node_ids = N/A

node_id = 4
parent_node_id = 1
child_node_ids = 8, 9

node_id = 5
parent_node_id = 2
child_node_ids = N/A

node_id = 6
parent_node_id = 2
child_node_ids = 10

node_id = 7
parent_node_id = 2
child_node_ids = N/A

node_id = 8
parent_node_id = 4
child_node_ids = N/A

node_id = 9
parent_node_id = 4
child_node_ids = 11, 12

[David]

David Byrne wrote:

> Okay, sorry to be somewhat unclear with my question.
> HereÂ’s some sample input data that may help to clear
> things up:
>
> #######################
> node_id = 0
> parent_node_id = N/A
> child_node_ids = 1, 2
>
> node_id = 1
> parent_node_id = 0
> child_node_ids = 3, 4
>
> node_id = 2
> parent_node_id = 0
> child_node_ids = 5, 6, 7
>
> node_id = 3
> parent_node_id = 1
> child_node_ids = N/A
>
> node_id = 4
> parent_node_id = 1
> child_node_ids = 8, 9
>
> node_id = 5
> parent_node_id = 2
> child_node_ids = N/A
>
> node_id = 6
> parent_node_id = 2
> child_node_ids = 10
>
> node_id = 7
> parent_node_id = 2
> child_node_ids = N/A
>
> node_id = 8
> parent_node_id = 4
> child_node_ids = N/A
>
> node_id = 9
> parent_node_id = 4
> child_node_ids = 11, 12
>
> #####...and so on #####
>
> Notes:
> - node_id = 0 is the root node.
> - N/A means no further relationships exist.
> - Only one parent exists for each child.
> - The 'child_node_id' is redundant data. There will
> be similar descriptive data for each node, but it
> isnÂ’t important for the structure of the tree.
>
> Question: How can I create a tree (i.e. a hash of
> hashes) given the above relationships?

although i haven't follow this thread close enough, the following seems to
be what you want:

#!/usr/bin/perl -w
use strict;

use Data::Dumper;

my %v; my $tree;

local $/ = '';

while(<DATA>){
my %t = map{y/ //d; split /=/} split /\n/;
$v{$t{node_id}} = $t{parent_node_id};
for(grep !/n.a/i, split(/,/,$t{child_node_ids})){
my($p,@k) = $t{node_id};
while($p){
push(@k,$p);
$p = $v{$p};
}
eval '$tree->{' . join('}->{',reverse $_,@k,0) . '}={}';
}
}

print Dumper($tree);

__DATA__

[data you provided above]

__END__

given your above data, the script prints:

$VAR1 = {
'0' => {
'1' => {
'4' => {
'8' => {},
'9' => {
'11' => {},
'12' => {}
}
},
'3' => {}
},
'2' => {
'6' => {
'10' => {}
},
'7' => {},
'5' => {}
}
}
};

david
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