in reply to Regular Expressions: Call for Examples

Here are 3 regexes i used recently for Node Link Checker. The problem is to turn PM link settings into their respective HTML links. First, the lookup table: 
my %TAG = (
   ftp     => 'ftp://',
   http    => 'http://',
   https   => 'https://',
   kobe    => 'http://theoryx5.uwinnipeg.ca/mod_perl/cpan-search?filet
+ype=+distribution+name+or+description&j&case=clike&search=',
   kobes   => 'http://theoryx5.uwinnipeg.ca/mod_perl/cpan-search?filet
+ype=+distribution+name+or+description&j&case=clike&search=',
   cpan    => 'http://search.cpan.org/search?mode=module&query=',
   isbn    => 'http://shop.barnesandnoble.com/booksearch/isbnInquiry.a
+sp?isbn=',   google  => 'http://www.google.com/search?q=',
   lucky   => 'http://www.google.com/search?btnI=I&q=',
   jargon  => 'http://www.science.uva.nl/cng/search/htsearch.CGI?restr
+ict=%2F%7Emes%2F&jargon%2Fwords=',
   id      => '/index.pl?node_id=',
   pad     => '/index.pl?node_id=108949&user=',
   DEFAULT => '/index.pl?node=',
);

[download]
Next, the regexes: 
# takes care of [tag://target|alt]
$chunk =~ s/\[(\w+):\/\/(.*?)\|([^\]]+)\]/<a href="$TAG{$1}$2">$3<\/a>
+/g;

# takes care of [tag://target]
$chunk =~ s/\[(\w+):\/\/([^\]]+)\]/<a href="$TAG{$1}$2">$2<\/a>/g;

# takes care of [target]
$chunk =~ s/\[([^\]]+)\]/<a href="$TAG{DEFAULT}$1">$1<\/a>/g;

[download]
The 3 regexes have to be executed in that order. Maybe they could be combined into one regex, but this worked for me. :)

jeffa

L-LL-L--L-LL-L--L-LL-L--
-R--R-RR-R--R-RR-R--R-RR
B--B--B--B--B--B--B--B--
H---H---H---H---H---H---
(the triplet paradiddle with high-hat)

Replies are listed 'Best First'.
Re: (jeffa) Re: Regular Expressions: Call for Examples
by jryan (Vicar) on Jul 22, 2002 at 01:56 UTC

    I wrote this mostly to annoy jeffa because of:

    they could be combined into one regex
    But, he insisted that I post this here :) 
    $chunk =~
s!
    \[
    (?(?= [^:]*://)
        (?:
            (\w+)://
            ([^|\]]+)
            (?:
                \| ([^\[]+)
            )?
        )
        |
        (\w+)
    )
    \]
!
$_ = "<a href=\"".((defined$1)?(qq($TAG{$1}$2">).((defined$3)?$3:$2)):
qq($TAG{DEFAULT}$4">$4))."</a>"!gex;

    [download]

    I truely think that jeffa's approach is better than the above. It's much smarter to break a 3 case problem into 3 steps rather than use 1 gigantic regex. Just look at the "substitution" section; its hidious (I'd normally have used a sub to handle the above "substitution" section, but then wouldn't be "one regex" :)

    .
[reply]
[d/l]

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