From: Robert Klemme <shortcutter@...>
Date: 2012-08-20T15:54:14+09:00
Subject: Re: case vs if-else

On Mon, Aug 20, 2012 at 6:57 AM, Charles Hixson
<charleshixsn@earthlink.net> wrote:

> The point was that because it's hard to tell what is fast and what is slow,
> bad decisions are often made.

The situation is not that bad.  For example, we know that - from a
certain number of entries on - it is much faster to use hash lookup
than sequential lookup.  Where exactly the point is from which on it's
faster depends on the specific situation (hit rate, hash functions
etc.).  Whether a particular piece of code is a significant
performance hog in a certain program can only be judged by measuring.
But sill it does make sense to use a Hash as general lookup tool which
generally will be quite good decision.

> I was using my current habit of avoiding
> regular expressions as an example of that.

There you have a bad habit IMHO.  Regular expressions are often faster
in Ruby because they are implemented in C and do not need to create as
many objects with GC overhead as any solution implemented in Ruby is
likely to have.

>  I had heard that the regular
> expression parser had been totally re-written, but because it would take a
> lot of work to find out the details, I tend to cling to an habit which may
> now be bad, even though it was once appropriate.

You do not need to know too many details; you could just try it out
and measure it, don't you think?

Cheers

robert


-- 
remember.guy do |as, often| as.you_can - without end
http://blog.rubybestpractices.com/