Cloning shared hashref

menth0l has asked for the wisdom of the Perl Monks concerning the following question:

I'm trying to clone shared hashref into non-shared one. But when i run this piece of code:

use threads;
use threads::shared;
use Clone;
use Data::Dumper;

my $x = shared_clone({
    a => 'Foo',
    b => 'Bar'
});

my $z = Clone::clone($x);
print Dumper($z);
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i get an error:

Can't locate object method "FETCH" via package "threads::shared::tie" 
+at C:/Perl/site/lib/Data/Dumper.pm line 190.
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Moreover, print keys %$z; prints "ab" but print values %$z; gives previous error. Can anyone explain to me what can i do to use $z as a normal hashref and what causes this error?

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Re: Cloning shared hashref by BrowserUk (Patriarch) on Jan 20, 2011 at 14:33 UTC
Storing a reference to a shared structure into a non-shared scalar isn't a good idea. Correct that and you get a clue as to the problem: `use threads; use threads::shared; use Clone; use Data::Dumper; my $x :shared = shared_clone({ a => 'Foo', b => 'Bar' }); my $z = Clone::clone($x); print Dumper($z); __END__ C:\test>junk25 Don't know how to handle magic of type \156 at C:\test\junk25.pl line +11.` [download] Basically, Clone has never been updated to work with shared data, which is rather more than normal tied data. This all begs the question of why you want to clone a shared structure to a non-shared? Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error. "Science is about questioning the status quo. Questioning authority". In the absence of evidence, opinion is indistinguishable from prejudice.	[reply] [d/l]
Re^2: Cloning shared hashref by menth0l (Monk) on Jan 20, 2011 at 14:44 UTC
This all begs the question of why you want to clone a shared structure to a non-shared? I don't want orignal to be changed by one of the threads. So i need o thread-local copy that can be modified at will.	[reply]
Re^3: Cloning shared hashref by BrowserUk (Patriarch) on Jan 20, 2011 at 15:48 UTC
Use this: `use threads; use threads::shared; use Data::Dumper; sub clone { my $ref = shift; my $type = ref $ref; if( $type eq 'HASH' ) { return { map clone( $_ ), %{ $ref } }; } elsif( $type eq 'ARRAY' ) { return [ map clone( $_ ),@{ $ref } ]; } elsif( $type eq 'REF' ) { return \ clone( $$ref ); } else { return $ref; } } my $x :shared = shared_clone({ a => 'Foo', b => 'Bar' }); my $z = clone( $x ); print Dumper( $z );` [download] Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error. "Science is about questioning the status quo. Questioning authority". In the absence of evidence, opinion is indistinguishable from prejudice.	[reply] [d/l]
Re^4: Cloning shared hashref by menth0l (Monk) on Jan 21, 2011 at 08:12 UTC
Re^5: Cloning shared hashref by BrowserUk (Patriarch) on Jan 21, 2011 at 08:39 UTC
Re^4: Cloning shared hashref by jwba (Novice) on Mar 16, 2011 at 21:43 UTC
Re^5: Cloning shared hashref by BrowserUk (Patriarch) on Mar 16, 2011 at 23:04 UTC
Some notes below your chosen depth have not been shown here
Re: Cloning shared hashref by locked_user sundialsvc4 (Abbot) on Jan 20, 2011 at 15:14 UTC
What you are looking for is called a deep copy. (Or, “deep cloning.”) e.g. `clone` in Storable. Hashes often contain references to things, and changing any one of the references changes the (one) thing to which it refers... “Holy `EQUIVALENCE`, Captain Fortran!”
Re^2: Cloning shared hashref by BrowserUk (Patriarch) on Jan 20, 2011 at 18:31 UTC
If you'd bothered to look, you'd have realised that the sole purpose of Clone`::clone()` is to perform deep copies. If you'd looked at Storable, you'd have discovered that it doesn't export a routine called `clone()`. And if you bothered to try `dclone()`, you'd have found that it produces exactly the same error.	[reply] [d/l] [select]