From: Josh Cheek <josh.cheek@...>
Date: 2012-02-03T12:47:01+09:00
Subject: Re: Basic Ruby performance

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On Thu, Feb 2, 2012 at 8:57 PM, Jeremy Bopp <jeremy@bopp.net> wrote:

>
> Try a similar change to the other looping variations that have been
> discussed and see if and how much they may improve.  For me I didn't
> really see any difference between using re as above or using the simple
> regexp directly; however, the code was almost an order of magnitude
> slower when I replaced the comparison as follows:
>
>  s =~ / test#{} /
>
> It seems that Ruby is smart enough to see that the simple regexp will
> never need to be re-evaluated.  The regexp used above must force that
> optimization off because #{} while constantly evaluated to the empty
> string is technically dynamic, thus the regexp needs to be re-evaluated
> in every iteration of the loop.
>
>
The o flag tells Ruby to only interpolate the first time, and then cache
the regex

s =~ / test#{} /o

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