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Re: Python's re module and genealogy problem

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From Thomas Rachel <nutznetz-0c1b6768-bfa9-48d5-a470-7603bd3aa915@spamschutz.glglgl.de>
Newsgroups comp.lang.python
Subject Re: Python's re module and genealogy problem
Date Wed, 11 Jun 2014 15:55:18 +0200
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Am 11.06.2014 14:23 schrieb BrJohan:

> Can it, for a pair of regular expressions be decided whether at least
> one string matching both of those regular expressions, can be constructed?
>
> If it is possible to make such a decision, then how? Anyone aware of an
> algorithm for this?

Just a feeling-based statement: I don't think that is easily possible.

Every RE can potentially match an infinite number of statements.

Just have a look at

re1 = re.compile('A43.*')
re2 = re.compile('.*[0-9][A-F]')

It can easily seen that the area these REs work on is different; they 
are orthogonal.

So there is an infinite number of strings these REs match.


Thomas

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Thread

Python's re module and genealogy problem BrJohan <brjohan@gmail.com> - 2014-06-11 14:23 +0200
  Re: Python's re module and genealogy problem Robert Kern <robert.kern@gmail.com> - 2014-06-11 14:26 +0100
    Re: Python's re module and genealogy problem Mark H Harris <harrismh777@gmail.com> - 2014-06-11 09:08 -0500
  Re: Python's re module and genealogy problem Thomas Rachel <nutznetz-0c1b6768-bfa9-48d5-a470-7603bd3aa915@spamschutz.glglgl.de> - 2014-06-11 15:55 +0200
  Re: Python's re module and genealogy problem Michael Torrie <torriem@gmail.com> - 2014-06-11 09:34 -0600
  Re: Python's re module and genealogy problem Nick Cash <nick.cash@npcinternational.com> - 2014-06-11 16:21 +0000
  Re: Python's re module and genealogy problem Simon Ward <simon@bleah.co.uk> - 2014-06-11 18:21 +0100
  Re: Python's re module and genealogy problem Vlastimil Brom <vlastimil.brom@gmail.com> - 2014-06-11 20:09 +0200
  Re: Python's re module and genealogy problem BrJohan <brjohan@gmail.com> - 2014-06-13 17:17 +0200
    Re: Python's re module and genealogy problem Peter Otten <__peter__@web.de> - 2014-06-13 18:26 +0200
    Re: Python's re module and genealogy problem Dan Sommers <dan@tombstonezero.net> - 2014-06-14 05:14 +0000
  Re: Python's re module and genealogy problem Tony the Tiger <tony@tiger.invalid> - 2014-06-14 08:35 +0000

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