From: Robert Klemme <shortcutter@...>
Date: 2008-09-09T00:04:20+09:00
Subject: Re: regular expression match and exclude

2008/9/8 Caleb Clausen <vikkous@gmail.com>:
> On 9/7/08, Peņa, Botp <botp@delmonte-phil.com> wrote:
>> irb(main):036:0> re2
>> => /galleries.*?([^t][^h][^u][^m][^b]).jpg/
>> irb(main):038:0> g.select{|x| x=~re2 }
>> => ["galleries/image1.jpg", "galleries/image2.jpg", "galleries/image3.jpg"]
>
> Unfortunately this way will fail to match (for instance) "bomb.jpg".
> If you want to go this route, you need to do something like this:
> (untested!)
>
> /^galleries.*([^t]humb|[^h]umb|[^u]mb|[^m]b|[^b])\.jpg$/   #bleah
>
> Patrick He wrote:
>> /^galleries\/((?!thumb).)+\.jpg$/
>
> Ah, brilliant! But it doesn't quite work. It fails to match
> "thumb_foo.jpg", which probably should match here. A simple
> modification should fix it, tho:
>
> /^galleries\/((?!thumb\.jpg$).)+\.jpg$/
>
> There. That's a pretty nice pure regexp.

Now just make the group non capturing and you're a tad more efficient. :-)

%r{\Agalleries/(?:(?!thumb\.jpg\z).)+\.jpg\z}

Cheers

robert


-- 
use.inject do |as, often| as.you_can - without end