Search and substitute into data structures

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

Hello,
I wanted to remove some common stuff from the text contained into some structures. I just came up with the attached code. However, is there anything simpler, maybe a search and substitute one-line instruction ?
Thank you.

use strict;
use warnings;
use Data::Dumper;

my $var = '<Country>&lt;![CDATA[US]]&gt;</Country>';
$var = unwrap_cdata($var);
print $var."\n";

my $hash = { america => '<Country>&lt;![CDATA[US]]&gt;</Country>',
             europe => ['<Country>&lt;![CDATA[IT]]&gt;</Country>','<Co
+untry>&lt;![CDATA[UK]]&gt;</Country>'],
           };

print Dumper $hash;

$hash = unwrap_cdata($hash);

print Dumper $hash;

sub unwrap_cdata {
    my $var = shift();

    if (ref($var)) {
        $var = unwrap_hash($var) if (ref($var) eq 'HASH');
        $var = unwrap_array($var) if (ref($var) eq 'ARRAY');
    } else {
        $var = unwrap_scalar($var);
    }
    return $var;
}
    sub unwrap_hash {
        my $href = shift();
        foreach my $key (keys %{$href}) {
            my $hk = $href->{$key};
            $hk = unwrap_hash($hk) if (ref($hk) eq 'HASH');
            $hk = unwrap_array($hk) if (ref($hk) eq 'ARRAY');
            $hk = unwrap_scalar($hk) if (not ref($hk));
            $href->{$key} = $hk;
        }
        return $href;
    }

    sub unwrap_array {
        my $aref = shift();
        my @array;
        my $i = -1;
        foreach my $av (@{$aref}) {
            $av = unwrap_hash($av) if (ref($av) eq 'HASH');
            $av = unwrap_array($av) if (ref($av) eq 'ARRAY');
            $av = unwrap_scalar($av) if (not ref($av));
            push @array,$av;
        }
        return \@array;

    }

    sub unwrap_scalar {
        my $var = shift();
        $var =~ s/<!\[CDATA\[//;
        $var =~ s/&lt;!\[CDATA\[//;
        $var =~ s/]]>//;
        $var =~ s/]]&gt;//;
        return $var;
    }
[download]

Comment on Search and substitute into data structures Download Code

Replies are listed 'Best First'.
Re: Search and substitute into data structures by Sidhekin (Priest) on Apr 30, 2007 at 19:05 UTC
Substitution is conceptually a destructive operation, particularly on structures, and that is how you use it, so I would rewrite your `unwrap_cdata` as explicitly so: `use strict; use warnings; use Data::Dumper; my $var = '<Country><![CDATA[US]]></Country>'; unwrap_cdata($var); print $var."\n"; my $hash = { america => '<Country><![CDATA[US]]></Country>', europe => ['<Country><![CDATA[IT]]></Country>','<Co +untry><![CDATA[UK]]></Country>'], }; print Dumper $hash; unwrap_cdata($hash); print Dumper $hash;` [download] If you ever really want to make copies, pass the copies to `unwrap_cdata` instead, and make sure you make deep copies (like with Storable::dclone). And now for my trick: `sub unwrap_cdata { for (@_) { eval { unwrap_cdata(@$_); 1 } and next; eval { unwrap_cdata(values %$_); 1 } and next; s/<!\[CDATA\[//; s/<!\[CDATA\[//; s/]]>//; s/]]>//; } }` [download] Recursion is fun. Block eval is great fun. :-) `print "Just another Perl ${\(trickster and hacker)},"` The Sidhekin proves Sidhe did it!	[reply] [d/l] [select]
Re^2: Search and substitute into data structures by rbi (Monk) on Apr 30, 2007 at 19:26 UTC
Thanks! And what about wrap_cdata, to wrap the content with <![CDATA ]> in the approach of your trick ?	[reply]
Re^3: Search and substitute into data structures by Sidhekin (Priest) on Apr 30, 2007 at 19:47 UTC
Thanks! And what about wrap_cdata, to wrap the content with [I assume] `<![CDATA[ ]]>` in the approach of your trick ? Same thing, as long as you know how to do it with a single string. Perhaps something like this: `sub wrap_cdata { for (@_) { eval { wrap_cdata(@$_); 1 } and next; eval { wrap_cdata(values %$_); 1 } and next; s/(?<![^>])([^<]+)/<![CDATA[$1]]>/g; } }` [download] Or not. I don't know why your original unwrap did not use the /g modifier. So please, season to taste. `print "Just another Perl ${\(trickster and hacker)},"` The Sidhekin proves Sidhe did it!	[reply] [d/l] [select]
Re: Search and substitute into data structures by merlyn (Sage) on Apr 30, 2007 at 18:52 UTC
You're missing a close curly brace just before `sub unwrap_hash`. Or at least, I hope you are, because otherwise, you're trying to create nested subroutines, which definitely don't work in Perl (at least not how mortals expect them to work). You have oddly indented the next subroutines, making me wonder if you really do have those "inside" the other subroutine. Have you seen Data::Visitor? I think it would abstract away most of what you're writing and rewriting, and let you concentrate on your transformations. -- Randal L. Schwartz, Perl hacker update: Yeah, you do have a broken subroutine-inside-a-subroutine. Please pull those out. Better yet, look at Data::Visitor.	[reply] [d/l]
Re^2: Search and substitute into data structures by rbi (Monk) on Apr 30, 2007 at 18:55 UTC
Sorry, I did not paste the last lines of the code.. I fixed it now.	[reply]
Re: Search and substitute into data structures by jwkrahn (Abbot) on Apr 30, 2007 at 19:59 UTC
You could use recursion to simplify that a bit: `sub unwrap_cdata { my @array; for ( @_ ) { if ( ref ) { push @array, ref eq 'ARRAY' ? [ unwrap_cdata( @$_ ) ] : ref eq 'HASH' ? { unwrap_cdata( %$_ ) } : ref eq 'SCALAR' ? \unwrap_cdata( $$_ ) : (); } else { ( my $var = $_ ) =~ s/<!\[CDATA\[//; $var =~ s/<!\[CDATA\[//; $var =~ s/]]>//; $var =~ s/]]>//; push @array, $var; } } return wantarray ? @array : $array[ 0 ]; }` [download]	[reply] [d/l]
Re: Search and substitute into data structures by ferreira (Chaplain) on Apr 30, 2007 at 19:04 UTC
You may try out Data::SearchReplace, a module whose 1.02 version was recently released. From the docs, it looks like it should be quite easy to do what you want using the module API. I would guess the solution you're looking for to be something like: `use Data::SearchReplace qw(sr); sr({ SEARCH => '<![CDATA[', REPLACE => '' }, $hash); sr({ SEARCH => '<![CDATA[', REPLACE => '' }, $hash); sr({ SEARCH => ']]>', REPLACE => '' }, $hash); sr({ SEARCH => ']]>', REPLACE => '' }, $hash);` [download]	[reply] [d/l]