[Linux-disciples] Negative Perl Regexp

[Chung-chieh Shan]

On 2004-07-22T15:56:07-0400, Adam Rosi-Kessel wrote:
> I guess I'm not entirely sure why the . is in there, though. Based on
> experimenting just now, if I omit the . then the negative fails, I guess
> because (?!ab) means "not ab" but you need to have something else in
> there to match?  I'm having trouble expressing this--is it that the
> (?!ab) collapses into nothingness for the purpose of the (?:) unit? Hmm.

(?!ab) means to check that there is no "ab" starting at the current
position (hence the term "negative lookahead assertion").  So, without
the . the regexp would mean, check that the string is comprised entirely
of empty strings where there is no "ab" starting.

> It's good to have you back, anyway.

Thanks!

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