bugGNU Octave - Bugs: bug #39431, regexp: documentation needs to be...


bug #39431: regexp: documentation needs to be expanded

Submitter:  Rik <rik5>
Submitted:  Mon 08 Jul 2013 12:08:54 AM UTC
Category:  Documentation Severity:  3 - Normal
Priority:  5 - Normal Item Group:  Documentation
Status:  Ready For Test Assigned to:  None
Originator Name:  Open/Closed:  * Open
Release:  * dev Operating System:  * Any
Fixed Release:  None Planned Release:  None
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Tue 27 Feb 2024 04:34:08 AM UTC, comment #7: 

added PRCE reference link in

if that seems sufficient, this can probably be closed.

Nicholas Jankowski <nrjank>
Group Member
Mon 26 Feb 2024 10:47:04 PM UTC, comment #6: 

I think the shorter text link is preferable.  If people want to go deep, then they can find more documentation.  But most people just want to quickly grab the basics.

Rik <rik5>
Group administrator
Mon 26 Feb 2024 10:02:13 PM UTC, comment #5: 

ok the pcre docs really just point to pcre2, and they've end-of-life'd pcre, so makes sense to point to some subset of


but much of that is sepcific to library use/installation, etc. to just reference matching/syntax/language related issues, maybe links to:

"Specification of the regular expressions supported by PCRE2"

and/or summary list:
"Syntax quick-reference summary"

Nicholas Jankowski <nrjank>
Group Member
Mon 26 Feb 2024 09:48:08 PM UTC, comment #4: 

haven't searched yet but assuming here's a doc location difference, we should point to PCRE or PCRE2?

Nicholas Jankowski <nrjank>
Group Member
Mon 26 Feb 2024 09:28:46 PM UTC, comment #3: 

I think this is a good idea.  It would be nice to have some self-contained documentation on regexp within Octave, but the reality is that almost everyone is connected to the Internet while coding and can go consult a reference.

Under the hood, Octave uses the Perl Compatible Regular Expression (PCRE) library.  Hence, pointing to Perl regexp documentation would be appropriate.  There are various sites that document regexp for various flavors such as Perl, POSIX, Java, etc.  That would be a worthy second choice.

Rik <rik5>
Group administrator
Mon 26 Feb 2024 09:12:20 PM UTC, comment #2: 

Don't think this has changed in a decade. 

All mention of regexp appears to be located here:


Is this something we can add an external reference to address? If we are just implementing e.g., the posix standard I don't think the octave docs need to be a full regexp reference except to capture what is unique/different.

Nicholas Jankowski <nrjank>
Group Member
Mon 21 Nov 2016 10:20:56 PM UTC, comment #1: 

This (documentation) seems to be still missing in Octave 4.2.0.

Hartmut <hardy>
Mon 08 Jul 2013 12:08:54 AM UTC, original submission:  

The documentation for regexp is missing some useful available features.  Here are some that I noticed.

1) Lookaround operators such as (?=), (?!), (?<=), (?<!)

2) POSIX character classes [[:class:]] where class might be "alpha" or "alnum" or ...

3) non-greedy (?) and atomic (+) adjectives for repetition quantifiers [*+?].

4) Backreferences in patterns such as \1 or \k<name>

5) Comments within patternns using (?# comment ) syntax

6) Discussion of escape sequence processing such as '\n' => newline.

7) Expanded discussion of named tokens

8) Conditional patterns based on prior subpattern capture

Rik <rik5>
Group administrator


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    Follow 3 latest changes.

    Date Changed by Updated Field Previous Value => Replaced by
    2024-02-27 nrjank StatusNeed Info Ready For Test
    2024-02-26 nrjank StatusConfirmed Need Info
    2013-07-08 rik5 StatusNone Confirmed

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