From: Caleb Clausen <vikkous@...>
Date: 2008-09-08T23:29:56+09:00
Subject: Re: regular expression match and exclude

On 9/7/08, Azalar --- <pteale@gmail.com> wrote:
> I am parsing a web page full of image links that also contain links to
> the thumbnails for those images.
>
> Here is my test data..
>
> galleries/image1.jpg
> galleries/image1thumb.jpg
> galleries/image2.jpg
> galleries/image2thumb.jpg
> galleries/image3.jpg
> galleries/image3thumb.jpg
>
> If i use this expression..
> /galleries.*(?=thumb).*jpg/
>
> The results are just those lines containing the word thumb.
>
> What I want to do is inverse this though and return only return that
> DONT contain the word thumb.

Using Reg, my DSL for declarative programming in ruby, you can use the
logical operators (& | ~) to combine regexps. I call this 'match
arithmetic'. The resulting objects implement === and =~, so they can
be used with Array#grep.

require 'rubygems'
require 'reg'
images=["galleries/foo.jpg", "galleries/foothumb.jpg"]
images.grep /galleries\/.*\.jpg$/ & ~/thumb\.jpg$/
   #in galleries and not thumb

There might well be a pure regexp way, but I've been unable to come up
with a clean one....