From: Tim Greer <tim@...>
Date: 2009-01-28T04:47:46+09:00
Subject: Re: A bug in Ruby regexp lib?

Tim Greer wrote:

> Artc5abras c5a0lajus wrote:
> 
>> ruby 1.8.7 (2008-08-11 patchlevel 72) [i486-linux]
>> 
>> x11@www:~$ irb
>> irb(main):001:0> s = "www.myspace.com/djmamania
>> www.myspace.com/djmantini"
>> => "www.myspace.com/djmamania www.myspace.com/djmantini"
>> irb(main):002:0> s1 = s.gsub(%r{(\s|^)(www\..*?)(\s|$)}m, '\1<a
>> href="http://\2">\2</a>\3')
>> => "<a
>>
>
href=\"http://www.myspace.com/djmamania\">www.myspace.com/djmamania</a>
>> www.myspace.com/djmantini"
>> irb(main):003:0> s1.gsub(%r{(\s|^)(www\..*?)(\s|$)}m, '\1<a
>> href="http://\2">\2</a>\3')
>> => "<a
>>
>
href=\"http://www.myspace.com/djmamania\">www.myspace.com/djmamania</a>
>> <a
>>
>
href=\"http://www.myspace.com/djmantini\">www.myspace.com/djmantini</a>"
>> 
>> Why I have to call gsub two times for this to work? Same regexp works
>> fine in Firefox JS :)
> 
> Did you mean:
> 
> s1 = s.gsub(%r{(^|\s)?(www\..*?)(\s|$)}m, '\1<a
> href="http://\2">\2</a>\3')
> 
> irb(main):035:0> s1 = s.gsub(%r{(^|\s)?(www\..*?)(\s|$)}m, '\1<a
> href="http://\2">\2</a>\3')
> => "<a
>
href=\"http://www.myspace.com/djmamania\">www.myspace.com/djmamania</a>
> <a
>
href=\"http://www.myspace.com/djmantini\">www.myspace.com/djmantini</a>"
> 
> Note the \1 is using (^|\s), as it's either the start of the string
> (^) or a white space between the two URLs (\s), but you also have \3,
> which is either the end of the string ($) or white space between the
> URLs (or following) (\s), and since there's only one white space
> between the two URLs, it throws is off.
> 
> To account for both \1 and \3, above I've set it to be optional
> (^|\s)?
> because this will allow you to use \3 without is breaking it.  There
> are other ways to do this, but just working with what you were using,
> that's a change you could make to get the desired results on the first
> one... unless I misunderstood what you were trying to do?

Geez, pardon the typos I've made above.  Apparently I'm having trouble
working my keyboard (some of those "is" should be "it")
-- 
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