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Re: Negative Lookahead Equivalent in emacs


From: luishenriquezperez
Subject: Re: Negative Lookahead Equivalent in emacs
Date: Wed, 10 May 2017 07:23:59 -0700 (PDT)
User-agent: G2/1.0

On Tuesday, May 9, 2017 at 5:54:29 AM UTC-4, Wasell wrote:
> On Mon, 8 May 2017 22:15:42 -0700 (PDT), in article <49e1dd7d-4be5-4b03-b9e2-
> address@hidden>, address@hidden wrote:
> > 
> > Hi,
> > 
> > I'm trying to write a regex that matches the last character of a sequence 
> > of non-whitespace characters '[^\n\r\t\f ]', or an empty line matching ^$. 
> > 
> > Thus: 
> > Hello World! --> "o" and "!" would be matched
> > 
> > In non-elisp regex languages I know the code for this is: \S(?!\S) 
> > I know that \S is equivalent too [^ /n/r/t/f]. 
> > But I'm unsure of what the elisp equivalent (if any) of the negative 
> > lookahead (?!).
> > 
> > I saw on this forum a post  "gnu.emacs.help ? regex nirvana - near miss"
> > Where Drew Adams said: "Typically, what you want to do for this in Emacs 
> > Lisp is to combine 
> > the use of a regexp for positive matching with other code that takes 
> > care of the non-matching (negation) need. "
> > 
> > However, I'm not sure how to go about doing this.
> 
> 
> If I'm not miss-understanding you completely, you want to match a non-
> whitespace, followed either a whitespace or an end-of-line. That would be:
> 
>       [^[:space:]]\(?:[[:space:]]\|$\)
> 
> Am I missing something?

No you're not missing anything. This one is a lot simpler :). 
Thank you.


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