From: "Ara.T.Howard" <Ara.T.Howard@...>
Date: 2005-09-03T00:21:25+09:00
Subject: Re: Ruby-specific performance heuristics?

On Sat, 3 Sep 2005, Robert Klemme wrote:

>> here's some things i think of:
>
> <lots of good stuff deleted>
>
>>    - anchor every single regular expression : performance degrades
>>      exponentially otherwise
>
> That's not possible - especially with String#scan.  Sometimes you want all
> occurrences of something.

true.  however there nearly always __some__ anchor one can use:

   harp:~ > irb
   irb(main):001:0> "foo bar".scan %r/ \b\w+ /x
   => ["foo", "bar"]

a better thing would be to say "use an anchor unless you know exactly why you
shouldn't."

>>    - compile regular expressions only once unless they require
>>      variable substitution
>
> I guess you're talking about flag /o or storage of a regexp object somewhere
> which is really only needed if the regexp contains interpolation that you
> want to do only once.  Otherwise a regexp *is* compiled only once and inline
> regexps are roughly as performant as a stored regexp and might be easier to
> read (not always).

you are quite right - guy pointed this out to me once before - for some reason
my brain hasn't retained it though ;-)

cheers.

-a
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