Copying a hash-of-hashes

From: Peter Rabbitson (rabbit_at_rabbit.us)
Date: 12/30/04

  • Next message: Alex Daniloff: "h2xs directory structure in perl-5.8.x?" 
    Date: Wed, 29 Dec 2004 22:58:17 -0500
To: beginners@perl.org

    Hello List,
    To explain the problem I am having, I wrote a simple snipet that doesn't do
    anything meaningful other than illustrating the behaviour I want to avoid:

    my %hoh = (
                1 => {
                    a => 5, b => 5
                    },

                2 => 5
               );

    my @res = &RANDOMSUB; #call a random subroutine

    print "$hoh{1}{a} $hoh{2} \n";

    sub RANDOMSUB {
        my %hohcopy = %hoh;

        $hohcopy{1}{a} = 2;
        $hohcopy{2} = 2;
    }

    >From my understanding since in the subroutine I am working with a local hash
    %hohcopy all the values assigned to it have no meaning in the main body.
    However the print produces 2, 5 instead of the desired 5, 5. As far as my
    understanding goes this is due to the fact that $hohcopy{1} holds a
    reference to $hoh{1} instead of recreating it's internal structure entirely
    from the root to the leaves while performing a copy.

    The question is whether there is an elegant way to produce a complete copy
    of a hash-of-hashes-of-hashes-...-of-hashes for internal subroutine purposes
    and make sure that all references will be translated properly as well,
    leaving the subroutine no ability to modify the main hash.

    Thank you.

    Peter

  • Next message: Alex Daniloff: "h2xs directory structure in perl-5.8.x?"

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