From: "Wolfgang Nádasi-Donner" <wonado@...>
Date: 2005-04-29T18:59:27+09:00
Subject: Re: Inverting a regular expression?

"Harry Ohlsen" <Harry_Ohlsen@hyperion.com> schrieb im Newsbeitrag
news:13AE96A47C1FF1498AEED9C5D6AEC449BA5E05@apsgpexm01.hyperion.com...
> A colleague of mine just asked me whether it was possible to invert an
> arbitrary regular expression.  Ie, create a new regular expression that
> matches whatever the original *didn't*.
>
It is impossible in general terms if you are talking about the usual "extended regular expressions" (I didn't
think about the "real regular expressions"). Take the RegEx

/(.{4})xy\1/

First of all - what does it mean to invert this expression?
Second - the pattern, that is produced by the RegEx is not static, it is build on results from applying parts
of the pattern.

I assume you can handle this by applying the RegEx (=pattern) to a string and use the MatchData-Object to find
out, what parts of the string are not matched.

Wolfgang N�dasi-Donner
wonado@donnerweb.de