Talk:Comparison of regular expression engines

message: https://pypi.python.org/pypi/regex supports a broader set of features than pythons standard re module, especially recursive pattern matching --ThomasKalka (talk) 11:02, 28 March 2016 (UTC)
replies: text: Linked in the "Remarks" column for Python in the Languages table. rootsmusic (talk) 22:36, 14 December 2023 (UTC)
thread_title:  python regex module missing 

message: Made some updates -- not enough room to document them on the 1 line summary.  Some of these address comments made previously (below).
Updates include:
* removing notes that something has only been available since '2007' (version was mentioned, but released 5 years ago)....
* remove notes on Unicode support where the note was (supports ALL, including binary )... if it supports it, it supports it, a special note should not be required for 'all', rather, only 'partial' support cases should be noted.
* modified ref-note for 'partial support' to indicate that such status was transient and that 'complete compliance' was dependent on updates after new versions are released.
* removed comparison columns for 'partial' matches and 'fuzzy matches' -- neither a feature of "*Regular* Expressions. The latter, which was defined, is specifically NOT a feature of regular expressions but rather an extra feature of some *products* that include a regex engine.  Comparing products that include regex's isn't the same thing as comparing regex'.  Though it wasn't defined, (how can you compare something that is 'undefined'), I believe it referred to a *product feature* in, for example something like 'vim', where it matches in your source text, whatever you have typed into a *search string*, in real time.   This isn't a feature of a regex engine, but a product feature of some *EDITORS* -- I.e. it's not about the 'RegEx Engine'.  I would wager that all of the products can match valid substring comprising a larger RegEx.  Equally, I would wager any program using those regex's could be programmed to ignore errors while things were being 'typed in'.  Thus -- irrelevant to this article.
* Notes: 1) 'Fuzzy' matching, involves fuzzy logic, which by definition is not a state-driven logic, and thus by definition cannot be part of a *Regular* expression engine.  It may, however be a product feature to allow various levels of 'mistakes' on matching the given RegEx, but the magnitude of mistake is not a binary property (thus fuzzy) -- thus not Regular.  Fuzzy logic is generally in the domain of "AI" - not regex's.
* Note 2: (not mentioned in the article) -- PCRE gets it's code from Perl -- so it's features generally track Perl's.  PCRE is an acronym for Perl Compatible Regular Expression. and the engine in ruby derives from PCRE -- and tries to track it's features.  The Ruby engine was done, specifically to add Japanese support BEFORE UTF-8 started becoming prevalent.  Thus it supported 16-bits early on, but for locale-based charsets for Japanese.  It wasn't really until it added UTF-8 support that it got full Unicode support.
 (This is written after updating ""Part 2"" .  I'm looking at ""Part 3"" to see what is salvageable there... started to writeup comments, but better I do it and then say what was done, as if I get hung up on saying what I'll do, I may not get it done...(am getting a bit tired of this update stuff already)...   Astara Athenea (talk) 21:44, 22 January 2012 (UTC)
thread_title:  Jan-2010 Update  

message: Too many of the terms used as headings are vague or apply only to the terminology used for one RE engine. What this article really needs is a glossary of its terms.
There's also a fair point to be made that many of the tables here could be prose, and that would facilitate citing them. -Harmil 19:47, 27 April 2007 (UTC)
thread_title:  Ill-defined terms 

message: Unless others disagree, I plan to remove from the comparison tables any flavors and engines which currently have no information about their features listed. Currently, this includes the following:
*ActionScript3.0
*Boost.Xpressive
*Grep
*GRETA
*Jakarta/Regexp
*Oniguruma
*SubEthaEdit
*Tcl 8.1
*TextMate
I would encourage others to list information about these engines' features, especially since a few of them are very significant and commonly used. However, I do not see any value in listing them without any information (none include any more than a couple "no"s). --Monger 00:54, 17 July 2007 (UTC)
replies: text: I've gone ahead and done this. --Monger 01:00, 20 July 2007 (UTC)
thread_title:  Removing flavors with no information 

message: I have not found any evidence, that Python supports unicode properties (like \p{L}). I'm not sure how it is about another implementations, so I am fixing only the Python item. See e.g. . Mykhal (talk) 21:10, 9 January 2008 (UTC)
thread_title:  Unicode property support 

message: What exactly is the Languages table supposed to show? Languages which have regexes builtin? Languages for which a regex library exists? Something else? As it stands today, it's completely meaningless. mathrick (talk) 00:30, 3 February 2008 (UTC)
replies: text: Languages which have regexes builtin --208.80.119.67 (talk) 03:32, 14 July 2011 (UTC)
thread_title:  Languages? 

message: I found the footnotes on these tables to be nigh on useless. Why are they using refun? I can see using refun when there are only one or two notes, but not when there are 7. I was forced to compare the link names on the endnotes with the notes themselves to figure out which note I was interested in reading. Argonel (talk) 21:43, 28 May 2008 (UTC)
thread_title:  Table footnotes 

message: Another interesting point of comparison could of course be speed (or type of implementation); some references in paper Regular Expression Matching Can Be Simple And Fast . --Lapo Luchini (talk) 14:58, 31 August 2008 (UTC)
thread_title:  Speed 

message: The note above Language Features part 1 states:
:NOTE: An application using a library for regular expression support does not necessarily offer the full set of features of the library, e.g. GNU Grep which uses PCRE does not offer lookahead support, though PCRE does.
However, the table shows that GNU Grep does support lookahead. Unfortunately, I'm not sure which is true, perhaps someone else who knows can correct it.  — Preceding unsigned comment added by 99.42.116.61 (talk) 22:03, 28 April 2013 (UTC)
thread_title:  Inconsistency between Language Features Part 1 and Note above 

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thread_title:  External links modified 

message: - There are official types of engines: DFA / NFA with the distinction Traditional NFA, Posix NFA (see. Mastering Regular Expressions, 3rd Edition by Jeffrey E.F. Friedl, chapter 4)
 - And there is a strong grouping of Perl compatibility (which drove regex developments some years ago). Perl 5.005 introduced new features (Perl 5.005 Regular Expression improvements) like Lookbehinds, Conditional Expressions, Atomic Groups. Perl 5.10 introduced other new features (Perl 5.1 Regular Expression improvements) many years later like Named Capture Buffers, Possessive Quantifiers, Relative Backreferences, \K, among others. The regex engine in version 5.10 was developed in collaboration with the PCRE project, the most interesting features were added beween 1997 and 2007 (Curated PCRE history).
As Perl is/was the defacto standard for regex, most of the engines in this Wikipedia article have a grammar and feature clearly set before the Perl 5.005 release, between Perl 5.005 and 5.10, or after Perl 5.10.
Sebastian --88.217.185.170 (talk) 21:47, 12 October 2019 (UTC)
replies: text: A bit of digging provided: PCRE was created 1997, when Perl 5.004 was out. PCRE 2.0 was created in 1998, when Perl 5.005 (with regex updates) was released. PCRE 7.0-7.3 were done in 2006-2007 in co-development for Perl 5.10 (with more groundbreaking regex updates). Sebastian --88.217.185.170 (talk) 22:20, 12 October 2019 (UTC)
thread_title:  Engines could be categorized 

message: I just tested regex "(?<=[a-z]+)[0-9]+" on some Java platforms, including Oracle JDK and OpenJDK 1.8, Oracle JDK and OpenJDK 17 at the text "abcd12345", and it gave the correct result "12345"; the variable-width look-ahead regex "[0-9]+(?=[a-z]+)" also works fine on Java on my machine. But on Android platform with API level 29 and Java source/target compatibility version 1.8, this regular expression has a compilation error for the reason of "non-fixed width look-behind". Also on the website regex test it fails with Java 8 flavor.
I don't know how these work on Java, and the different results above, very confused now.  — Preceding unsigned comment added by Bczhc (talk • contribs) 02:52, 5 February 2022 (UTC)
replies: text: and is there a need to add "variable-length lookahead" future property on regular expression features part 2? Bczhc (talk) 02:57, 5 February 2022 (UTC)
thread_title:  About Java Regex Variable-length lookaround