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Copying reference data without dereferencing

Posted on 1998-09-11
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Last Modified: 2010-03-05
In a program I am writing, I have a 3D array of hashes implemented through extensive use of references.  One of my procedures makes changes to the underlying data in that structure.  However, I would like to keep a second copy of the original structure in memory in order to restore it if needed.  I could do this with loops by dereferencing every element of the structure but I figure this is expensive in terms of processing time.

Is there a way to simply take a reference to a structure and generate a second reference to a completely separate but identical structure?  I suspect there is not, but if there is, it would be worth 100 points.

Colin
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Question by:colind
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by:ozo
ID: 1204826
perldoc -q copy
Found in perlfaq4.pod

How do I print out or copy a recursive data structure?


The Data::Dumper module on CPAN is nice for printing out
data structures, and FreezeThaw for copying them.  For example:

    use FreezeThaw qw(freeze thaw);
    $new = thaw freeze $old;

Where $old can be (a reference to) any kind of data structure you'd like.
It will be deeply copied.
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by:colind
ID: 1204827
Basically, ozo, you're the king.

Why don't you claim your points?

Colind
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ozo earned 100 total points
ID: 1204828
If so, maybe the FAQ should deserve the royaltys
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