Path: csiph.com!weretis.net!feeder6.news.weretis.net!news.misty.com!news.iecc.com!.POSTED.news.iecc.com!nerds-end From: Roger L Costello Newsgroups: comp.compilers Subject: Question about regex with negated character class Date: Mon, 25 Apr 2022 12:48:43 +0000 Organization: Compilers Central Lines: 23 Sender: news@iecc.com Approved: comp.compilers@iecc.com Message-ID: <22-04-015@comp.compilers> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 8bit Injection-Info: gal.iecc.com; posting-host="news.iecc.com:2001:470:1f07:1126:0:676f:7373:6970"; logging-data="57597"; mail-complaints-to="abuse@iecc.com" Keywords: lex, question, comment Posted-Date: 25 Apr 2022 12:33:08 EDT X-submission-address: compilers@iecc.com X-moderator-address: compilers-request@iecc.com X-FAQ-and-archives: http://compilers.iecc.com Accept-Language: en-US Content-Language: en-US Xref: csiph.com comp.compilers:2981 Hi Folks, On page 12 of the Flex specification it says this: "A negated character class such as [^A-Z] will match a newline unless \n (or an equivalent escape sequence) is one of the characters explicitly present in the negated character class (e.g., [^A-Z\n]). This is unlike how many other regular expression tools treat negated character classes ..." Is that last sentence true? Does Flex behaves differently from other regex engines, with regard to negated character class? I just tested the [^A-Z] regex at (https://regex101.com/) and every regex engine on that web page matches a string containing a newline. In other words, Flex behaves just like all the other regex engines. I conclude that that last sentence in the Flex manual is not correct. Do you agree? /Roger [It may have been true 30 years ago but they all match \n in a pattern now. On the other hand, grep won't match a newline because it does the matching one line at a time. -John]