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Groups > comp.lang.java.programmer > #28558

Re: regex tidy

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On 25.05.2014 18:09, Roedy Green wrote:
> On Sat, 24 May 2014 14:55:03 +0200, Robert Klemme
> <shortcutter@googlemail.com> wrote, quoted or indirectly quoted
> someone who said :

>>> 3. alphabetise | lists.
>> What does that mean?  Are you talking about merging common prefixes to
>> get a more efficient matching experience?  That might actually be done
>> by a regex engine if it detects this situation.
>
>
> (cat|rabbit|dog|cow)
> could be transformed to
> (cat|cow|dog|rabbit)
>
> for two reasons:
> make the list easier to proofread
> might help engine optimise handling the c in cat and cow in common.

The engine does not need the reordering to do this optimization.  If you 
want to help lesser engines which do not optimize here you would have to 
transform it into

(c(?:at|ow)|dog|rabbit)

to get more efficient matching.

Cheers

	robert

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Thread

regex tidy Roedy Green <see_website@mindprod.com.invalid> - 2014-05-23 11:39 -0700
  Re: regex tidy leif.roar@invalid.com (Leif Roar Moldskred) - 2014-05-23 14:33 -0500
    Re: regex tidy Joshua Cranmer 🐧 <Pidgeot18@verizon.invalid> - 2014-05-23 15:05 -0500
  Re: regex tidy Robert Klemme <shortcutter@googlemail.com> - 2014-05-24 14:55 +0200
    Re: regex tidy Roedy Green <see_website@mindprod.com.invalid> - 2014-05-25 09:09 -0700
      Re: regex tidy Robert Klemme <shortcutter@googlemail.com> - 2014-05-25 18:49 +0200
        Re: regex tidy leif.roar@invalid.com (Leif Roar Moldskred) - 2014-05-25 12:28 -0500
          Re: regex tidy Robert Klemme <shortcutter@googlemail.com> - 2014-05-25 19:55 +0200
          Re: regex tidy "Chris Uppal" <chris.uppal@metagnostic.REMOVE-THIS.org> - 2014-05-26 12:12 +0100
    Re: regex tidy Roedy Green <see_website@mindprod.com.invalid> - 2014-05-25 09:10 -0700
    Re: regex tidy Roedy Green <see_website@mindprod.com.invalid> - 2014-05-25 09:13 -0700
    Re: regex tidy Roedy Green <see_website@mindprod.com.invalid> - 2014-05-25 09:21 -0700
      Re: regex tidy Joshua Cranmer 🐧 <Pidgeot18@verizon.invalid> - 2014-05-25 13:31 -0500
        Re: regex tidy "Chris Uppal" <chris.uppal@metagnostic.REMOVE-THIS.org> - 2014-05-26 12:31 +0100

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