0000793: Regular Expressions: add REG_MINIMAL and a minimum repitition modifier

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Category

Severity

Type

Date Submitted

Last Update

0000793

[1003.1(2013)/Issue7+TC1] Base Definitions and Headers

Editorial

Enhancement Request

2013-11-15 14:37

2024-06-11 09:02

Reporter

steffen

View Status

public

Assigned To

ajosey

Priority

normal

Resolution

Accepted

Status

Closed

Name

steffen

Organization

User Reference

Section

Vol 1. 9.4.6, Vol. 1. 13. regex.h, Vol 2. regcomp(), Vol. 4. A.9.2

Page Number

190, 322, 1783, 3501

Line Number

6195, 10781, 57428, 118310

Interp Status

---

Final Accepted Text

Summary

0000793: Regular Expressions: add REG_MINIMAL and a minimum repitition modifier

Description

The current POSIX regular expressions only offer a very restricted set of functionality, which forces many, if not most, real-life programs to use
external regular expressions libraries which add features like non-greediness,
positive and negative lookaround assertions and Unicode compatibility.

Some Open Group members already ship with regular expression facilities which support at least some of the extensions, and there exist long-proven, stable and free (also for commercial use, BSD-licensed), almost drop-in, alternatives which can be used by the others (see the mailing list for some references).

Desired Action

- Vol. 1: Base Definitions, Chapter 9, «Regular Expressions».

  9.4.6 EREs Matching Multiple Characters, p. 190, line 6195:
  insert after

        6. Each of the duplication symbols (’+’, ’*’, ’?’, and intervals) may
           be suffixed by the minimal repitition modifier ’?’ <question-mark>,
           in which case matching behaviour is changed from the «leftmost
           longest possible match» to the «leftmost shortest possible match»,
           including the null match
           (see [reference to A.9, p. 3500 ff.]). For example, the ERE ".*c"
           matches the last character (’c’) in the string "abc abc", whereas
           the ERE ".*?c" matches the first character ’c’, the third character
           in the string.

           If the REG_MINIMAL flag, as defined in the <regex.h>[REF] header,
           is used when compiling an ERE via regcomp(3)[REF], the «leftmost
           shortest possible match» is the default, and the minimal repitition
           modifier ’?’ can be used to select the «leftmost longest possible
           match».

  change, on (current) line 6195 ff.,

        The behavior of multiple adjacent duplication symbols (’+’, ’*’, ’?’,
        and intervals) produces undefined results.

  to

        The behavior of multiple adjacent duplication symbols (’+’, ’*’, ’?’,
        and intervals, possibly suffixed by the minimal repitition modifier)
        produces undefined results.

- Vol. 1: Base Definitions, Chapter 13, «Headers».

  On p. 322, line 10781
  insert after

        REG_MINIMAL Change default matching behaviour to »leftmost shortest
                possible match». Only applicable to REG_EXTENDED regular
                expressions.

- Vol. 2: System Interfaces.

  On p. 1783, line 57428
  insert after

        REG_MINIMAL Change default matching behaviour to »leftmost shortest
                possible match». Only applicable to REG_EXTENDED regular
                expressions.

- Vol. 4: Rationale (Informative),
  A.9.2 «Regular Expression General Requirements».

  On p. 3501, line 118310
  insert after

        EREs can optionally use a «leftmost-shortest» rule (enabled via
        the REG_MINIMAL flag and/or the ’?’ minimal repitition modifier), in
        which case the «shortest possible matching prefix» is instead
        identified as the matching sequence.

Tags

issue8

Attached Files

Relationships

parent of

0001329

Closed

Problem in resolution of 0000793: "Regular Expressions: add REG_MINIMAL and a minimum repitition modifier"

Notes
(0002092) Don Cragun (manager) 2013-12-21 20:56	It is not possible to make changes to an approved TC and the page and line numbers don't match TC1 either. This bug has been moved from project 2008-TC1 with category Rationale to project 1003.1(2013)/Issue7+TC1 with category Base Definitions and Headers.

(0004807) geoffclare (manager) 2020-03-30 08:40	When applying this bug I spotted that "up to" was missing from the item 6 addition to 9.4.6 and inserted it. The source currently has: For example, the ERE .sG ".c" matches up to the last character (\c .cH c ) in the string .sG "abc abc" , whereas the ERE .sG ".?c" matches up to the first character .cH c , the third character in the string. (I also fixed the spelling of "repetition").

Issue History
Date Modified	Username	Field	Change
2013-11-15 14:37	steffen	New Issue
2013-11-15 14:37	steffen	Status	New => Under Review
2013-11-15 14:37	steffen	Assigned To	=> ajosey
2013-11-15 14:37	steffen	Name	=> steffen
2013-11-15 14:37	steffen	Section	=> Vol 1. 9.4.6, Vol. 1. 13. regex.h, Vol 2. regcomp(), Vol. 4. A.9.2
2013-11-15 14:37	steffen	Page Number	=> 190, 322, 1783, 3501
2013-11-15 14:37	steffen	Line Number	=> 6195, 10781, 57428, 118310
2013-12-21 20:48	Don Cragun	Project	2008-TC1 => 1003.1(2013)/Issue7+TC1
2013-12-21 20:56	Don Cragun	Interp Status	=> ---
2013-12-21 20:56	Don Cragun	Note Added: 0002092
2013-12-21 20:56	Don Cragun	Category	Rationale => Base Definitions and Headers
2014-01-09 17:15	Don Cragun	Status	Under Review => Resolved
2014-01-09 17:15	Don Cragun	Resolution	Open => Accepted
2014-01-09 17:15	Don Cragun	Tag Attached: issue8
2020-03-25 15:58	geoffclare	Status	Resolved => Applied
2020-03-29 13:50	rhialto	Issue Monitored: rhialto
2020-03-29 23:03	Don Cragun	Relationship added	parent of 0001329
2020-03-30 08:40	geoffclare	Note Added: 0004807
2024-06-11 09:02	agadmin	Status	Applied => Closed

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