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 seems like quite a difficult problem to me, but maybe I'm just not
looking at it the right way.

Obviously simple cases are easy. Eg

   re = /[a-z]/
   inverse = /[^a-z]/

However, I think it would be much harder for arbitrary cases.  Eg, how
would one automatically invert something like the following

   /<[^<>]*id="!?(region8-).*?>/

Note that I'm not talking about finding lines that don't contain the
pattern (a la "grep -v"); I'm talking about finding all the occurrences
within a single line that don't match it.

Inquisitively yours,

Harry O.


************************************************************************

If you have received this e-mail in error, please delete it and notify the sender as soon as possible. The contents of this e-mail may be confidential and the unauthorized use, copying, or dissemination of it and any attachments to it, is prohibited. 

Internet communications are not secure and Hyperion does not, therefore, accept legal responsibility for the contents of this message nor for any damage caused by viruses.  The views expressed here do not necessarily represent those of Hyperion.

For more information about Hyperion, please visit our Web site at www.hyperion.com