dotnet/runtime

Regex - Support Possessive Quantifiers

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#24,381 opened on Dec 7, 2017

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 (9 comments) (5 reactions) (0 assignees)C# (5,445 forks)batch import
area-System.Text.RegularExpressionsenhancementhelp wanted

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Description

Current popular regex engines like java.util.regex or PCRE support greedy, lazy and possessive quantifiers. The current .NET regex engine does only support the former two. Though possessive quantifiers are syntactic sugar and can be mimicked with atomic grouping today, consider supporting them as they gained popularity over the last years.

Abstract: Possessive quantifiers work the same as greedy quantifiers but without backtracking on the input string. That means that the following pattern D++[A-Z]+ matches the input string DDDDE but not DDDD.

Contributor guide

Research direction
Investigate how the .NET regex engine currently implements greedy and lazy quantifiers, and how atomic groups work. Then design a new syntax for possessive quantifiers and implement it following the same pattern.
Tech stack
csharp
Domain
backend
Issue type
Feature
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-2 days
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
Active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Clear
Prerequisites
C#Git
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
50