School Assignment? Project Due Tomorrow? Chat LIVE With A Programming Expert!

Dream.In.Code > Programming Help > Other Languages

Welcome to Dream.In.Code
	Become an Expert! Join 307,089 Programmers for FREE! Get instant access to thousands of experts, tutorials, code snippets, and more! There are 2,073 people online right now. Registration is fast and FREE... Join Now! Chat LIVE With a Expert

RegEx non-capture groups question

RegEx non-capture groups question

NickDMax	2 Nov, 2009 - 09:52 AM Post #1
Can grep dead trees! Joined: 18 Feb, 2007 Posts: 5,267 Thanked: 293 times Dream Kudos: 1175 Expert In: Java/C++ My Contributions	Given: "hello world" and a regex: (?<!h)(\w+) why does the regex find "hello"? I thought I was asking it to find words that don't begin with h. Note I don't need a regex to find words that don't begin with h -- I am just trying to understand the negative lookback. If I wanted to find words that didn't begin with h I would use something like: [^h](\w+) So the question is on using the (?<! ) non-capture group which does not seems to function the way I think it should (I have tested this in a number of languages so it is not a bug in the particular library as I initially thought).
	This Post Was Helpful!

Register for Free to Make These Ads Go Away!

NickDMax	RE: RegEx Non-capture Groups Question 2 Nov, 2009 - 01:53 PM Post #2
Can grep dead trees! Joined: 18 Feb, 2007 Posts: 5,267 Thanked: 293 times Dream Kudos: 1175 Expert In: Java/C++ My Contributions	Sorry... as usual I discovered my answer on my own. "hello" is a match for (\w+) and it is not preceded by an h... however if the input string was "hhello world" we would match "hhello" because it is not preceded by an h (it is preceded by the start of the string). didn't think it though
	This Post Was Helpful!

Fast Reply

Reply to this topic

Start new topic

Display Mode: Standard · Switch to: Linear+ · Switch to: Outline

Track this topic · Email this topic · Print this topic · Subscribe to this forum

Time is now: 11/21/09 11:20AM

Invision Power Board v2.1.7 © 2009 IPS, Inc.

Licensed to: MediaGroup1

Advertising | Terms of Use | Privacy Policy | About Us | Site Map

Advertise on this site through Lake Quincy Media

Forum Index: Programming Help | C and C++ | VB6 | Java | VB.NET | C# | ASP.NET | PHP | ColdFusion | Perl and Python | Ruby | Databases | Other Languages | Game Programming | Mobile Development | Software Development | Computer Science | Industry News | Programming Tutorials | C++ Tutorials | Visual Basic Tutorials | Java Tutorials | VB.NET Tutorials | C# Tutorials | Linux Tutorials | PHP Tutorials | ColdFusion Tutorials | Windows Tutorials | HTML/JavaScript Tutorials | CSS Tutorials | Flash Tutorials | Web Promotion Tutorials | Graphic Design & Photoshop Tutorials | Software Development Tutorials | Database Tutorials | Other Language Tutorials | ASP.NET Tutorials | Game Programming Tutorials | WPF & Silverlight Tutorials |

Copyright 2001-2008 MediaGroup1 LLC, All Rights Reserved
A MediaGroup1 LLC Production - Version 6.0.2.1.36
Server: secure2

Search^Updated!w00t

Over 509,000 Pages! Advanced Forum Search

Live Help!

Be Social

Tutorials

Programming

Web Development

Reference Sheets

Code Snippets

DIC Chatroom

Join our IRC Chat

Bye Bye Ads

Monthly Drawing

Top Contributors

Top 10 Kudos This Month