From: Wes Gamble <weyus@...>
Date: 2006-05-25T00:03:56+09:00
Subject: Re: String.scan hangs in some cases?

Bill Kelly wrote:
> From: "Robert Klemme" <shortcutter@googlemail.com>
>> 
>> Yes, that's a property of NFA based regular expression engines.  Some
>> patterns have awful runtime characteristics because of the
>> backtracking.  Without looking too close at your patter I guess in
>> this case it's caused by having "x*" twice in your RX - not very
>> useful anyway.
> 
> Thanks :)  We haven't seen the OP's regexp yet; I was just
> offering the above as an example of what can cause the
> hanging he described.
> 
> 
> Regards,
> 
> Bill

All,

Thanks for giving me some idea of what might be wrong.  For now, I've 
gone with a simpler regex that I think will work fine.  My original 
pattern was attempting to allow several portions of the pattern to be 
optional and the more that I think about it, the more it makes sense 
that this might occur.

I will keep (?>pattern) in mind as a way to inhibit backtracking.

Thanks,
Wes

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