Re: negative lookbehind and VERY strange capture

Expanding out your regex it becomes obvious

use strict;
use warnings;

my $s = '"toto"';
if ($s =~ 
    m[^
        (?<!\\)"
        (
            (
                (?<=\\)"|[^"]
            )+                         # $2
        )                              # $1
        (?<!\\)"
    $]x
) {
  print "It matches!\n";
  print $1 . "\n";
  print $2 . "\n";
}
[download]

You have two nested pairs of capturing parens, the inner pair with a repeat. So the outer pair captures everything matched by the inner repetition, and the inner pair captures the last thing it matches. Hence "toto" and the last character of that "o".

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Comment on Re: negative lookbehind and VERY strange capture Download Code

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Re^2: negative lookbehind and VERY strange capture by Denis.Beurive (Initiate) on Sep 18, 2016 at 11:53 UTC
Hello BrowserUK, Thank you very much for your answer. I just learn something. I put « non-capturing parentheses » and it did the trick : `my $s = '"abcd"'; print "Try for \"$s\":\n"; if ($s =~ /^(?<!\\)"((?:(?<=\\)"\|[^"])*)(?<!\\)"$/) { print "It matches!\n"; print '$1: ' . $1 . "\n"; print '$2: ' . (defined($2) ? "\$2 is defined\n" : "\$2 is NOT defin +ed\n"); } else { print "It does not match!\n"; }` [download] However, as Corion pointed out, my regular expression does not work for this string « `abcd\\` ». I’ll try some new approaches. Best regards Denis	[reply] [d/l] [select]

Replies are listed 'Best First'.

Re^2: negative lookbehind and VERY strange capture
by Denis.Beurive (Initiate) on Sep 18, 2016 at 11:53 UTC

Hello BrowserUK,

Thank you very much for your answer. I just learn something. I put « non-capturing parentheses » and it did the trick :

my $s = '"abcd"';
print "Try for \"$s\":\n";
if ($s =~ /^(?<!\\)"((?:(?<=\\)"|[^"])*)(?<!\\)"$/) {
  print "It matches!\n";
  print '$1: ' . $1 . "\n";
  print '$2: ' . (defined($2) ? "\$2 is defined\n" : "\$2 is NOT defin
+ed\n");
} else {
  print "It does not match!\n";
}
[download]

However, as Corion pointed out, my regular expression does not work for this string « abcd\\ ». I’ll try some new approaches.

Best regards

Denis

[reply]
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[select]