Re: Match nothing in grep { ! // }

Yeah , and then what? What is your question?

The empty regex always matches

$ perl -Mre=debug -e " m//"
Compiling REx ""
Final program:
   1: NOTHING (2)
   2: END (0)
minlen 0
Matching REx "" against ""
   0 <> <>                   |  1:NOTHING(2)
   0 <> <>                   |  2:END(0)
Match successful!
Freeing REx: ""

$ perl -Mre=debug -e " $_ = q/fi/; m//"
Compiling REx ""
Final program:
   1: NOTHING (2)
   2: END (0)
minlen 0
Matching REx "" against "fi"
   0 <> <fi>                 |  1:NOTHING(2)
   0 <> <fi>                 |  2:END(0)
Match successful!
Freeing REx: ""
[download]

Comment on Re: Match nothing in grep { ! // } Download Code

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Re^2: Match nothing in grep { ! // } by bart (Canon) on Mar 14, 2013 at 12:07 UTC
The empty regex always matches Well, yes, and no. // is special, it serves as a shortcut, as if it's not the first regex you match, it signifies a repeat of the last regex that matched. perlreref: If 'pattern' is an empty string, the last successfully matched regex is used. In your tests here, there was no previous match, so this rule doesn't apply.	[reply]
Re^2: Match nothing in grep { ! // } by ag4ve (Monk) on Mar 14, 2013 at 08:20 UTC
I'm writing a scraper and sometimes I need to exclude some data. As I said, doing: `$css->{xlink} //= ' ';` [download] works in this case but it just doesn't seem like the right way to do this. `@{$ret->{link}} = grep { ! /$css->{xlink}/ } map { $_->{href} } $dom-> +find($css->{link})->each if ($css->{link});` [download]	[reply] [d/l] [select]
Re^3: Match nothing in grep { ! // } by McA (Priest) on Mar 14, 2013 at 09:21 UTC
IMHO my post should have helped you as it showed that you can extend the expression in the grep codeblock. But now we know a little more of your problem and I assume the following: If `$css->{xlink}` is defined and not empty you want to try a match. The otherwise clause is not obvious to me, but you can change it. E.g. `grep { $css->{xlink} && ! /$css->{xlink}/ }` [download] I hope I understood it right. McA	[reply] [d/l] [select]
Re^3: Match nothing in grep { ! // } by Anonymous Monk on Mar 14, 2013 at 09:58 UTC
I'm writing a scraper and sometimes I need to exclude some data. ... Well, that much (your desire) was clear from your original post, but its still not a question :) If you want to filter based on a regex, and a space isn't adequate, what is adequate? ?? if( sometingTrue ){ grep filter } else { no grep filter } Or were you after what McA wrote?	[reply]