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From: Devin Jeanpierre <jeanpierreda@gmail.com>
Date: Fri, 24 May 2013 09:13:41 -0400
Subject: Re: Utility to locate errors in regular expressions
To: Malte Forkel <malte.forkel@berlin.de>
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On Fri, May 24, 2013 at 8:58 AM, Malte Forkel <malte.forkel@berlin.de> wrote:
> As a first step, I am looking for a parser for Python regular
> expressions, or a Python regex grammar to create a parser from.

the sre_parse module is undocumented, but very usable.

> But may be my idea is flawed? Or a similar (or better) tools already
> exists? Any advice will be highly appreciated!

I think your task is made problematic by the possibility that no
single part of the regexp causes a match failure. What causes failure
depends on what branches are chosen with the |, *, +, ?, etc.
operators -- it might be a different character/subexpression for each
branch. And then there's exponentially many possible branches.

-- Devin