Re: Monks' Expression

I've only got a moderate amount of experience working with perl, so my coding isn't always the best, but here's one approach to it...

my $text = "Here is [id=327]a very cool document[/id] for you";
$text =~ /\[id=([0-9]*)\](.*)\[\/id\]/i;
my $tag = "<A HREF=\"/cgi-bin/coolcode.pl?id=$1\">$2</A>";
my $before = $`;
my $after = $';

print "$before$tag$after\n";
[download]

If you actually put this in a file and run it with Perl, you'll get:

Here is <A HREF="/cgi-bin/coolcode.pl?id=327">a very cool document</A>
+ for you
[download]

Just as you'd expect and (hopefully) want. :-)

Comment on Re: Monks' Expression Select or Download Code

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Re: Re: Monks' Expression by eg (Friar) on Jan 22, 2001 at 13:34 UTC
Interesting. As has been mentioned before, `.` here is bad because it's greedy and will prevent you from finding two matches on a line. Furthermore, `.` is usually pretty inefficient -- the regexp has to match everything to the end of the line and then start backtracking to try to match whatever follows the `.`. (`.?` is better but still less than ideal to because it needs to look ahead one character in every step. If '`[`' is only allowed in tags, then `[^[]*` is the best.) Also, why use `$before` and `$after` rather than $` and `$'` directly? Of course, if at all possible, you shouldn't be using $` and `$'` at all (see Why does using $&, $`, or $' slow my program down? in perlfaq6). Cheers, mate!	[reply]
Re: Re: Re: Monks' Expression by Segfault (Scribe) on Jan 22, 2001 at 23:51 UTC
I used $before and $after because often, I've found, I end up using multiple regexps in one block of code, and I need to easily get back to those values from prior matches. Thanks for the tips though, I was hoping for some advice on my regexps. :-)	[reply]