How do I pass refs to tied vars ?

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

Is it possible to pass on tied vars by reference ? I would think the following code works, but it doesn't :(

use strict;
use Tie::Hash::Stack;

my (%a, %b);

tie %a, 'Tie::Hash::Stack';
print( (tied(%a) ? 'tied' : 'NOT tied'), " a\n");

*b = \%a;
print( (tied(%b) ? 'tied' : 'NOT tied'), " b\n");
[download]

--
Jaap Karssenberg || Pardus (Larus)? <pardus@cpan.org>
>>>> Zoidberg: So many memories, so many strange fluids gushing out of patients' bodies.... <<<<

Comment on How do I pass refs to tied vars ? Download Code

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Re: How do I pass refs to tied vars ? by broquaint (Abbot) on May 19, 2003 at 15:15 UTC
Globs are not lexical (unless diotalevi is involved ;) e.g `use strict; use Tie::Hash; my(%a, %b); tie %a, 'Tie::StdHash'; print( (tied(%a) ? 'tied' : 'NOT tied'), " my %a\n"); *b = \%a; print( (tied(%main::b) ? 'tied' : 'NOT tied'), " %main::b\n"); print( (tied(%b) ? 'tied' : 'NOT tied'), " my %b\n"); __output__ tied my %a tied %main::b NOT tied my %b` [download] As you can see your problem is that you're testing the lexical `%b` and not the package `%b`. HTH `_________ broquaint`	[reply] [d/l]
Re: How do I pass refs to tied vars ? by japhy (Canon) on May 19, 2003 at 15:36 UTC
Oooh! Use Lexical::Alias! `use Tie::Hash::Stack; use Lexical::Alias; tie my(%a), 'Tie::Hash::Stack'; alias %a => my(%b);` [download] That's if you're using Perl 5.8+. If you're below that, do: `use Tie::Hash::Stack; use Lexical::Alias 'alias_h'; tie my(%a), 'Tie::Hash::Stack'; alias_h %a => my(%b);` [download] Shameless plug. _____________________________________________________ Jeff`[japhy]`Pinyan: Perl, regex, and perl hacker, who'd like a job (NYC-area) `s++=END;++y(;-P)}y js++=;shajsj<++y(p-q)}?print:??;`	[reply] [d/l] [select]
Re: How do I pass refs to tied vars ? by Zed_Lopez (Chaplain) on May 19, 2003 at 18:00 UTC
Or there's always, in fact, using an actual reference. `$b = \%a; print( (tied(%$b) ? 'tied' : 'NOT tied'), " b\n");` [download] This produces the expected results.	[reply] [d/l]
Re: How do I pass refs to tied vars ? by gmpassos (Priest) on May 19, 2003 at 19:40 UTC
As everyone said, GLOB aren't lexical. In your code, you make tied(%b), where %b isn't %main::b, it's my (%b). So, to fix your code, just change: `## From: my(%a, %b); ## To: my %a ; use vars qw(%b) ;` [download] And now you can see the output: `tied a tied b` [download] If you want to work with the reference to the tied HASH, use: `my $b = \%a; tied(%$b) ;` [download] Or use Lexical::Alias, as japhy said. :-P Graciliano M. P. "The creativity is the expression of the liberty".	[reply] [d/l] [select]