Path: csiph.com!usenet.pasdenom.info!weretis.net!feeder4.news.weretis.net!feeder1.news.weretis.net!news.tota-refugium.de!.POSTED!not-for-mail From: Thomas Rachel Newsgroups: comp.lang.python Subject: Re: Python's re module and genealogy problem Date: Wed, 11 Jun 2014 15:55:18 +0200 Organization: A not so newly installed InterNetNews server Lines: 25 Message-ID: References: Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit X-Trace: tota-refugium.de 1402495202 23234 eJwNyMkBwCAIBMCWBDncciC4/ZcQ5zm+Q+JLCw9zOqH1cYlI3C11kd4Dus/JNDJterOxQyuykfGeWllLWo6hh+m3FAf9Mo4KDu/05cYa/I8IHls= (11 Jun 2014 14:00:02 GMT) X-Complaints-To: abuse@news.tota-refugium.de NNTP-Posting-Date: Wed, 11 Jun 2014 14:00:02 +0000 (UTC) User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:24.0) Gecko/20100101 Thunderbird/24.5.0 Hamster/2.1.0.11 X-User-ID: eJwFwYEBwCAIA7CXqlCEcxja/09YQosVczwYTlG9oQy13QEGrzoHLN7leZV9htv7fUorNfADKDMRiQ== In-Reply-To: Cancel-Lock: sha1:a/daN9zeTBwFrZ6cwyGNa0lfmLQ= X-NNTP-Posting-Host: eJwFwYEBwCAIA7CXgErRc5jS/09YkqDz1mJypVJjR+IxOb7afe3AZsboQH+ax6ZXjH/aRO8sheHVvI5c0xfzPBIa2YmAzt5xnQ2n56ofrEUeHw== Xref: csiph.com comp.lang.python:73174 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