Re: [Ctags] lookahead operators supported?

[Elliott H. <en...@je...>]

On Mon, 2007-04-02 at 23:47 -0400, Joseph Xu wrote:
> I'm trying to define some tags for a custom language, and I was
> wondering of negative lookahead operators of the type (?!<regex>) is
> supported by ctags. I tried a regex like this:
> 
> /^\(\s*<=\s*\(\s*(?!next)([a-zA-Z0-9_]+)/\1/e,elab/
> 
> and got the message "ctags: Warning: Invalid preceding regular expression".
> 
> But if I remove the negative lookahead and use this:
> 
> /^\(\s*<=\s*\(\s*([a-zA-Z0-9_]+)/\1/e,elab/
> 
> it works fine. Am I using the right syntax?

ctags uses regcomp(3), which only supports "POSIX" regular expressions.
see the output of "man 7 regex" on a Linux box for details.

if you need a more Perl-like ctags, you could use the PCRE library. i
think you should be able to just change ctags' #includes to grab
<pcreposix.h>.

-- 
Elliott Hughes, http://www.jessies.org/~enh/