recursively passing hash reference

thealienz1 has asked for the wisdom of the Perl Monks concerning the following question:

I am currently working on code that creates something simliar to a trie structure. My implementation is pretty much trying to create a hash of hash, etc... which should be a problem as I believe I have enough memory.

I have come to a bit a pickle though. It might be that I have been working on this program for awhile and that it is late, but I have come to stopping point. For the life of my I am not able to implement a simple hash reference recursion. Let me explain with my code and expected output.

use strict;
use Data::Dumper;

my $start;

sub add{
    my $root = shift;
    my $level = shift;
    my @items = @_;
    if(!@items) {return;}
    #print "level = $level\n";
    while(@items) {
        my $first = shift @items;
        $root->{$first}->{count}++;
        #print "\t" x $level . "first = " . $first . ", values = " . j
+oin(',',@items)."\n";
        add($root->{$first}->{children}, $level+1, @items);
    }
}

add($start, 1, 1..3);
add($start, 1, 1..2);

print Dumper($start);
[download]

Expected output

$VAR1 = {
          '1' => {
                   'children' => {
                            '2' => {
                              'children' => {
                                          '3' => { 'count'=>1}
                                },
                        'count' => 2},
                    '3' => {'count' => 1}
                    },
                   'count' => 2
                 },
          '3' => {
                   'count' => 1
                 },
          '2' => { 'children' => {
                  '3' => {
                    'count' => 1
                }
            },
                   'count' => 2
                 }
        };
[download]

I realize its probably something really trivial that I am missing here, but any help is a appreciated.

Thanks

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Re: recursively passing hash reference by planetscape (Chancellor) on Apr 03, 2006 at 09:25 UTC
atcroft has a very nice recursive function here which can handle a multilevel data structure consisting of arrays, hashes, and scalars. Perhaps you can adapt it to your needs or at least use it as a reference for constructing your own. HTH, planetscape	[reply]
Re: recursively passing hash reference by thealienz1 (Pilgrim) on Apr 03, 2006 at 07:49 UTC
Alright, just an update. I believe I have found the problem. use strict; use Data::Dumper; my $start = {}; sub add{ my $root = shift; my $level = shift; my @items = @_; if(!@items) {return $level-1;} #print "level = $level\n"; while(@items) { my $first = shift @items; $root->{$first}->{count}++; if(!exists($root->{$first}->{children})) {$root->{$first}->{ch +ildren}={};} #print "\t" x $level . "first = " . $first . ", values = " . j +oin(',',@items)."\n"; $root->{$first}->{max} = add($root->{$first}->{children}, $lev +el+1, @items); } } add($start, 1, 1..4); add($start, 1, 1..2); print Dumper($start); [download] I was passing hash reference that were undefined, which is not a good thing apparently. So, I fixed that problem.	[reply] [d/l]