Re: regex: Need help substituting

If you have an other way of achieving the result I need, I'd be happy to learn about it.

In general, using an XML parser is preferable to using regular expressions. All parsers require an investment in time to learn, and XML::Twig is a good choice:

use warnings;
use strict;
use XML::Twig;

my $x = '<map>
    <section1>
        <parameter>Some text</parameter>
        <rstate>CHANGE_THIS</rstate>
    </section1>
    <section2>
        <subsection>
            <parameter>dont change this</parameter>
            <rstate>CHANGE_THIS</rstate>
        </subsection>
        <subsection>
            <parameter>dont change this</parameter>
            <rstate>DONT CHANGE THIS</rstate>
        </subsection>        
        <subsection>
            <parameter>dont change this</parameter>
            <rstate>CHANGE_THIS</rstate>
        </subsection>
    </section2>
    <section3>
        <parameter>dont change this</parameter>
        <rstate>DONT CHANGE THIS</rstate>
    </section3>
</map>
';

my $t = XML::Twig->new(
    twig_handlers => { rstate => \&rstate },
    pretty_print  => 'indented',
);
$t->parse($x);
$t->print();

sub rstate {
    my ($t, $rstate) = @_;
    my $text = $rstate->text();
    $text =~ s/CHANGE_THIS/CHANGED/;
    $rstate->set_text($text);
}

__END__


<map>
  <section1>
    <parameter>Some text</parameter>
    <rstate>CHANGED</rstate>
  </section1>
  <section2>
    <subsection>
      <parameter>dont change this</parameter>
      <rstate>CHANGED</rstate>
    </subsection>
    <subsection>
      <parameter>dont change this</parameter>
      <rstate>DONT CHANGE THIS</rstate>
    </subsection>
    <subsection>
      <parameter>dont change this</parameter>
      <rstate>CHANGED</rstate>
    </subsection>
  </section2>
  <section3>
    <parameter>dont change this</parameter>
    <rstate>DONT CHANGE THIS</rstate>
  </section3>
</map>
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Comment on Re: regex: Need help substituting Download Code

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Re^2: regex: Need help substituting by the_perl (Initiate) on Apr 07, 2012 at 14:20 UTC
Thanks for your reply! That would work using the parser, given all values need to be changed are the same? If they differ I would need several instances of the parser? If I'm not mistaken the parser approach builds around the idea that I already know the value, which is not my case. I need to read the old value, do some calculations and reinsert the new value. I realize my example was not optimal, sorry for that. In reality all values are not neccecarily the same. I still would like to know how this would be achieved using regexp. Thanks again, Pontus	[reply]
Re^3: regex: Need help substituting by mbethke (Hermit) on Apr 07, 2012 at 21:50 UTC
You can do whatever calculations you like in the XML::Twig tag handler. Trying to do this with regexen is like hammering in a screw---you can do it but it's neither the easiest nor the most adequate way, so just don't.	[reply]
Re^3: regex: Need help substituting by toolic (Bishop) on Apr 07, 2012 at 16:48 UTC
I realize my example was not optimal OK, so show us a better example of what you are trying to do, what you have tried, and how it doesn't work for you.	[reply]