Passing Hashes by Reference

This was bugging me for AGES ! So I thought I would register and give something back to the Monks.... This snippet does four things:

Passes a Hash by reference (function b)

Adds some key/value pairs to the hash

Prints the hash using a recursive function (so the hash can be in any form, i think)

Passes (in effect) the hashes within the main hash to the recursive function.

It's taken me a while to work out references in perl. I hope it is useful to someone.

#!/opt/bin/perl5

my %c;

b(\%c);

#print as normal
if(0)
{
    for $i (keys %c)
    {
        print "$i = $c{$i}\n";
        for $a (keys %{$c{$i}})
        {
            print "$i = $c{$i} = $c{$i}{$a}\n";
        }
    }
}

sub b
{
    my($c)=@_;
    
    $$c{b} = 'b';
    $$c{c} = 'c';
    
    $$c{b}{a} = 'ba';
    $$c{b}{v} = 'bv';
    $$c{b}{v}{g} = 'bvg';
    
    print "printing c{b}{v} = $$c{b}{v}\n";
    
    recref($c,"");
}

#pass this function a reference to a hash
sub recref
{
    my($cref,$str)=@_;
    my $i;
    my $prefix;
    
    for $i (keys %{$cref})
    {    
        $prefix = $str . "." . $i;
        print "$prefix = $$cref{$i}\n";
        recref($cref->{$i},$prefix);
    }
}
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Comment on Passing Hashes by Reference Download Code

Replies are listed 'Best First'.
Re: Passing Hashes by Reference by belg4mit (Prior) on Jan 10, 2002 at 00:06 UTC
Heh heh heh heh, Where's Perl? Anyways, what's the purpose of this really? Did you ever read perlref or perlreftut? The 3rd thing the snippet done is done by Data::Dumper You could simply reassign `$str` there is no need for `$prefix`; `$str .= "." . $i;` `-- perl -pe "s/\b;([st])/'\1/mg"`	[reply] [d/l]
Re: Re: Passing Hashes by Reference by jamesdmorris (Sexton) on Jan 10, 2002 at 16:10 UTC
hah, I don't administer the machines... In reply... Yes I have read the documents, but found them a little confusing. I'm sure I'm not the only one... examples always help. I am familiar with Data::Dumper, but, the function is pretty small, and does not require Data::Dumper to be installed on the machines which I do not administer. ;) string re-assignment, yep, I should have done that :)	[reply]