From: Carlos <angus@...>
Date: 2005-03-24T11:08:06+09:00
Subject: Re: (Maybe) a simple question about regex

[Sam Kong <sam.s.kong@gmail.com>, 2005-03-24 02.49 CET]
> Hello!
> 
> I think that I am missing a very simple concept about regex.
> 
> s = '0123456789'
> s.scan(/\d\d/) #-> ["01", "23", "45", "67", "89"]
> 
> Now I want to exclude "45".
> How can I express it in the regex?
> When it's only one character, I can use ^.
> But for 2 characters, I don't think I can use it.

You can use a "negative lookahead assertion":

s.scan(/(?!45)\d\d/)

This means, at every point the regex tries to match, "if the next two
characters aren't "45", match \d\d".

HTH.
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