Talk:Raku rules

asymmetry in example

The example code for the language $\{a^{n}b^{n}c^{n}:n\geq 1\}$ seems asymmetrical in its requirements, in that it disallows additional trailing cs (<!before c>) but not additional leading as (<!after a>).

I would have expected either that neither constraint be applied, or that both be, or (stronger) that the whole be anchored to start and end of string. Am I missing something? Hv 11:59, 27 February 2007 (UTC)

This is a difference in style between programming examples and pure CS examples. In pure CS, you typically assume that the pattern is "rooted" at the start of the input. Programming languages that implement regular expressions (or rules, in this case) go a step further and re-apply the expression, starting at every token in the input sequence. I'll make a note in the text to clarify this. -Harmil 14:07, 27 February 2007 (UTC)

Actually, you have a point, and in reviewing the text, I realized that you don't need the trailing assertion at all to make the example. For example's sake you don't care about the surrounding context, you just want to match an even number of as, bs and cs. The last example did just that, and thus was different from the first two. No need for that. -Harmil 14:18, 27 February 2007 (UTC)

The "Implementation" section implies that whitespace is significant with the "rule" keyword, but the $\{a^{n}b^{n}c^{n}:n\geq 1\}$ example has whitespace in its rule definitions, which wouldn't create the correct grammar if whitespace was significant.

Just for fun, I backported the rules to Perl 5 syntax:

   $S = qr/(?=(??{$A})(?!b))a+(??{$B})/;
   $A = qr/a(??{$A})?b/;
   $B = qr/b(??{$B})?c/;

Would it be possible to have an example that can't be implemented in Perl 5? --60.36.179.50 (talk) 06:17, 17 February 2009 (UTC)

Blacklisted Links Found on the Main Page

Cyberbot II has detected that page contains external links that have either been globally or locally blacklisted. Links tend to be blacklisted because they have a history of being spammed, or are highly innappropriate for Wikipedia. This, however, doesn't necessarily mean it's spam, or not a good link. If the link is a good link, you may wish to request whitelisting by going to the request page for whitelisting. If you feel the link being caught by the blacklist is a false positive, or no longer needed on the blacklist, you may request the regex be removed or altered at the blacklist request page. If the link is blacklisted globally and you feel the above applies you may request to whitelist it using the before mentioned request page, or request it's removal, or alteration, at the request page on meta. When requesting whitelisting, be sure to supply the link to be whitelisted and wrap the link in nowiki tags. The whitelisting process can take its time so once a request has been filled out, you may set the invisible parameter on the tag to true. Please be aware that the bot will replace removed tags, and will remove misplaced tags regularly.

Below is a list of links that were found on the main page:

• http://www.programmersheaven.com/2/Perl6-FAQ-Regex

  Triggered by \bprogrammersheaven\.com\b on the global blacklist

If you would like me to provide more information on the talk page, contact User:Cyberpower678 and ask him to program me with more info.

From your friendly hard working bot.—cyberbot II ^Notify_Online 18:21, 8 December 2013 (UTC)

 Resolved This issue has been resolved, and I have therefore removed the tag, if not already done. No further action is necessary.—cyberbot II ^Notify_Online 20:59, 1 October 2014 (UTC)