Re^2: regex anchoring issue

in reply to Re: regex anchoring issue
in thread regex anchoring issue

Why do you place the regex in a (?>...) non-backtracking group?

Comment on Re^2: regex anchoring issue Download Code

Replies are listed 'Best First'.
Re^3: regex anchoring issue by kcott (Archbishop) on Feb 16, 2013 at 05:58 UTC
Wrapping regexp alternations in `(?>...)` is something I do by default. While there may be rare cases where this might be problematical, I haven't encountered any: it's something that doesn't hurt and, indeed, often helps. This usage is based on a "Perl Best Practices" guideline: Backtracking (page 269). It's summarised on page 271 as: ... rewrite any instance of: `X \| Y` [download] as: `(?> X \| Y )` [download] While I'm not a slave to all "Perl Best Practices" guidelines, this is one I have found to be useful. Update: `s/have encountered/haven't encountered/` -- Ken	[reply] [d/l] [select]

Replies are listed 'Best First'.

Re^3: regex anchoring issue
by kcott (Archbishop) on Feb 16, 2013 at 05:58 UTC

Wrapping regexp alternations in (?>...) is something I do by default. While there may be rare cases where this might be problematical, I haven't encountered any: it's something that doesn't hurt and, indeed, often helps.

This usage is based on a "Perl Best Practices" guideline: Backtracking (page 269). It's summarised on page 271 as:

... rewrite any instance of:

X | Y
[download]

as:
(?> X | Y )
[download]

While I'm not a slave to all "Perl Best Practices" guidelines, this is one I have found to be useful.

Update: s/have encountered/haven't encountered/

-- Ken

[reply]
[d/l]
[select]

In Section Seekers of Perl Wisdom