From: ml.morus.walter@... (Morus Walter)
Date: 2006-10-24T13:40:10+09:00
Subject: Re: DRY fanatics?

In article <newscache$bemi7j$uw2$1@cat-in-the-hat.dnsalias.com>,
	"Ken Bloom" <kbloom@gmail.com> writes:
> On Sun, 22 Oct 2006 10:02:37 +0900, Giles Bowkett wrote:
> 
>> Anybody know a way to make this DRYer?
>> 
>>     when /^([A-Za-z0-9,]+), '([^']+)', '([^']+)', '([^']+)'/
>> 
>> a literal regex with a subpattern repeated three times
>> 
>> I could probably split on the ', but it seems that might have unwanted
>> side effects.
>>
> 
> That's fine. I see no reason to make it more obfuscated. A couple tips
> though:
> 
>  * Use .+? instead of [^']+
>    .+? does a non-greedy match, which is what you're really trying to say
>    with the [^']+
> 
Really?
What about input like
"bla, 'bl'ub', 'foo', 'bar'"

You'll easily see that the non-greedy version matches, whereas the
original regex doesn't.
You have to be *very* careful if you use non-greedy matches instead of
explicit exclusion, when the match is followed by further rules.
/'[^']+'/ and /'.+?'/ are equivalent, but /'[^']+',/ and /'.+?',/ are not.

My rule of thumb is to avoid non greedy matches in complex regexes.

M.