Talk:Regular expression

From Wikipedia, the free encyclopedia
Jump to navigation Jump to search
WikiProject Computing / Software / CompSci (Rated C-class, High-importance)
WikiProject iconThis article is within the scope of WikiProject Computing, a collaborative effort to improve the coverage of computers, computing, and information technology on Wikipedia. If you would like to participate, please visit the project page, where you can join the discussion and see a list of open tasks.
C-Class article C  This article has been rated as C-Class on the project's quality scale.
 High  This article has been rated as High-importance on the project's importance scale.
Taskforce icon
This article is supported by WikiProject Software (marked as High-importance).
Taskforce icon
This article is supported by WikiProject Computer science (marked as High-importance).
 
WikiProject Computer science (Rated C-class, High-importance)
WikiProject iconThis article is within the scope of WikiProject Computer science, a collaborative effort to improve the coverage of Computer science related articles on Wikipedia. If you would like to participate, please visit the project page, where you can join the discussion and see a list of open tasks.
C-Class article C  This article has been rated as C-Class on the project's quality scale.
 High  This article has been rated as High-importance on the project's importance scale.
 

Bad choice of example image/regex[edit]

The example image's regex uses lookaheads/lookbehinds without them being defined anywhere in the article!

I realise this is a result of edits to the image's original caption over time, but the image should probably be removed, or definitions added. — Preceding unsigned comment added by Swith22 (talkcontribs) 22:16, 2 May 2018 (UTC)

Regex "[^"]*+" in possessive matching not gives a different result than "[^"]*" in lazy matching. Tejasvi Singh Tomar (talk) 13:40, 4 June 2019 (UTC)

Typos in the formal definition, or a significant omission of English articles?[edit]

(Kleene star) R* denotes the smallest superset of set described by R that contains ε and is closed under string concatenation. This is the set of all strings that can be made by concatenating any finite number (including zero) of strings from set described by R. 11:03, 17 October 2018 (UTC)

  • Since R is subject to change, the bolded material above should read a set described by R, no?
  • Please inform (and forgive) me if this usage was intentional.

Mczuba (talk) 11:03, 17 October 2018 (UTC)

You are right, there should be an article. Since R describes exactly one set, it should even be "the". Thanks for noticing! - Jochen Burghardt (talk) 15:09, 17 October 2018 (UTC)

"Regex" isn't a universally agreed on distinguishing name[edit]

The text suggests that "regular expressions" in the modern software sense aren't actual "regular expressions" in the mathematical sense (this is demonstrably true) and that they are actually "regexes". This is misleading. There are those who use the term "regex" to mean "modern software regular-expression-like engines" (this was first clearly articulated in the early 2000s as far as I know, by Larry Wall when developing Perl 6 Rules and has gained some traction). But it's trivial to find counter-examples in the literature.

Here is a researcher referring to mathematical regular expressions as "regexes":

  • Yang, Yi-Hua E., and Viktor K. Prasanna. "Space-time tradeoff in regular expression matching with semi-deterministic finite automata." 2011 Proceedings IEEE INFOCOM. IEEE, 2011.

And here is a Google patent that refers to software regular expressions with seemingly arbitrary alternation between the two terms:

  • Chen, Jian, and Xinyu Hu. "Regular expression matching method and system." U.S. Patent No. 8,756,170. 17 Jun. 2014.

You can see that there's just no consensus in Google Scholar search (results above from page 2) and Wikipedia really should not be used to try to assert one where it does not exist...

-Miskaton (talk) 20:32, 7 August 2019 (UTC)

promotional edits for the RE2 library[edit]

See the WP:MOS for guidance on ''See Also. This is a topic on regular expressions, which is not the same as a list of applications which implement regular expressions. TEDickey (talk) 11:10, 28 November 2019 (UTC)

What authority has standardized regular expressions[edit]

The Patterns section says standard textual syntax. I know that there are definitions of regular expressions within the POSIX standard but that is for within POSIX. Where is the authority saying that the definition within the POSIX standard applies outside of POSIX? Sam Tomato (talk) 21:40, 19 March 2020 (UTC)