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Date:      Sun, 16 Apr 2017 22:43:26 +0200
From:      Joerg Sonnenberger <joerg@bec.de>
To:        freebsd-hackers@freebsd.org
Subject:   Re: Replacing libgnuregex
Message-ID:  <20170416204326.GA24950@britannica.bec.de>
In-Reply-To: <20170416134756.GA88424@stack.nl>
References:  <CACNAnaEmBjWudEJwvRTSqyciOp7-oRbCEQ_e6qtGsap0oHQ4yw@mail.gmail.com> <20170416134756.GA88424@stack.nl>

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On Sun, Apr 16, 2017 at 03:47:56PM +0200, Jilles Tjoelker wrote:
> On Tue, Apr 11, 2017 at 03:20:58PM -0500, Kyle Evans wrote:
> > On the other hand, I think I could fairly easily implement most of these
> > into libc/regex. Here's a summary of what this option entails adding to
> > libc/regex, from what I've found:
> 
> > [snip]
> > * Add backreferences (\1 through \9) to EREs
> > [snip]
> 
> Adding this enforces that EREs, like BREs, may sometimes require
> exponential time to match. I would prefer to avoid that.

The Spencer RE doesn't need backreferences to be exponential, but I
certainly agree that adding support for them makes it more difficult to
change to a better RE implementation later.

Joerg



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