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

Why the following code does not work : 
use Devel::Pointer;

my %hash;
$hash{1} = 2;

my $code = &create(\%hash);
print "CODE : ".$code."\n";

my $ref = &extract($code);
print "REF : ".$ref."\n";

sub create {
    my $self = shift;
    return(address_of($self));
}
sub extract {
    my $self = shift;
    return(deref($self));
}

[download]
Another question is why each time I use the address_of method the return value is different for the same reference. Is there a way to decode this value so I can use it as an hash key ?

Replies are listed 'Best First'.
Re: How do I use Devel::Pointer in different scopes ?
by broquaint (Abbot) on Mar 31, 2002 at 14:25 UTC
    In &create() you get the address of the value in $hash{1}, which is only available within that scope. So when you try and dereference it in &extract() perl breaks because you're trying to dereference a non-existant value.
    However if you directly pass address_of() $hash{1}, you'll get the expected reference. So this code will work 
    use strict;
use Devel::Pointer;

my %hash;
$hash{foo} = "bar";

my $ref = address_of($hash{foo});
print "reference : ".$ref."\n";

my $val = deref($ref);
print "value : ".$val."\n";

__output___

reference : 9900396
value : bar

    [download]
    The reason why you get a different reference value from address_of() each time is because you're creating a new scope, and a new value, so the reference will always be different.
    I really wouldn't recommend using Devel::Pointer for day-to-day reference munging (hence the Devel), you ain't using C no more kid ;-) For some authoritative information on references in perl check out perlref.
    HTH

    broquaint

[reply]
[d/l]

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