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

Wise Monks,

I'm having some trouble with a RegEx that matches within a <coordinates> (KML) tag... 

$kmlfile = "<coordinates>1.0001,2.0002,0 3.0003,4.0004,0 ...</coordina
+tes>";

if ($kmlfile =~ m{<coordinates>(.*)</coordinates>}g)
     {
     $coordinates = $1;
     while ($coordinates =~ m/\G(\d*\.\d*,\d*\.\d*),0*/s*/gs)
          {
          push @coords, $1;
          }
     }

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The only problem with this is that @coords only gets the first pair (1.0001,2.0002).

How do I populate each element with pairs as shown below? I thought that the \G operator would hold the previous search's last position and start from there on the next iteration to fill the array. 

$coords[0] = 1.0001,2.0002;
$coords[1] = 3.0003,4.0004;
...

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Your insight is most appreciated.

Replies are listed 'Best First'.
Re: \G inline RegEx operator
by almut (Canon) on Jun 03, 2008 at 22:42 UTC 
    m/\G(\d*\.\d*,\d*\.\d*),0*s*/gs
                          ^

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    I think you just have a typo in your regex: s should be \s

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      Thanks almut, I lost the "\" in translation, but it's presence still doesn't solve my problem...

      Highest Regards

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        Hm, works fine for me... i.e. when I add 

        ...
use Data::Dumper;
print Dumper \@coords;

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        to your code as is (but with the \s fixed), I do get 

        $VAR1 = [
          '1.0001,2.0002',
          '3.0003,4.0004'
        ];

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Re: \G inline RegEx operator
by johngg (Canon) on Jun 03, 2008 at 23:17 UTC
    I don't think that the \G is really necessary.

    use strict;
use warnings;

use Data::Dumper;

my $kmlfile = <<'EOD';
<coordinates>1.0001,2.0002,0 3.0003,4.0004,0 5.0005,6.0006,0
7.0007,8.0008,0 9.0009,10.0010,0
</coordinates>
EOD

my $rxCoord = qr
   {(?x)
       (?<=\s|>)
       (\d*\.\d*,\d*\.\d*)
       (?=,0)
   };
my @coords = $kmlfile =~ m{$rxCoord}g;

print Data::Dumper->Dumpxs( [ \ @coords ], [ q{*coords} ] );

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    The output.

    @coords = (
            '1.0001,2.0002',
            '3.0003,4.0004',
            '5.0005,6.0006',
            '7.0007,8.0008',
            '9.0009,10.0010'
          );

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    I hope this is of use.

    Cheers,

    JohnGG

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Re: \G inline RegEx operator
by pc88mxer (Vicar) on Jun 03, 2008 at 23:23 UTC
    Your method is fine, but here's how I would first approach this problem. It's based on some assumptions about how the coordinate data looks, so it may not be usable for you. However, I think the process of developing it is simpler, and perhaps it's even a little more robust. 
    if ($kmlfile =~ m{<coordinates>(.*?)</coordinates>}) {
  my @triples = split(' ', $1);
  for (@triples) {
    my ($lat, $long) = split(',', $_);
    push(@coords, [$lat, $long]); # or whatever
  }
}

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    It's a little more robust in that if there is non-conforming data it will be obvious (like one of your coordinates will be undef or contain junk.) Regex approaches have a tendency to just stop giving you results without any hint that there's a problem. That is, when they stop matching you're not sure if it's because there's nothing more to match or if there's a problem with your regex.
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Re: \G inline RegEx operator
by AF_One (Novice) on Jun 03, 2008 at 23:34 UTC

    Thanks so much guys, it's great to have this kind of support as a beginner...

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