From: Robert Klemme <shortcutter@...>
Date: 2012-02-03T19:42:44+09:00
Subject: Re: Basic Ruby performance

On Fri, Feb 3, 2012 at 3:21 AM, Dmitry Nikiforov <dniq@dniq-online.com> wrote:
> Ryan Davis wrote in post #1043813:
>
>> IMHO re.match is just as useless as Regexp.new, Array.new, and Hash.new
>> (assuming no args/blocks passed). They're throwbacks to java devs and
>> serve no purpose but to make things more verbose. In this specific case,
>> there are tangible reasons to use =~ over #match.
>
> The reason I tried to use Regexp.new is because I figured it would
> pre-compile the regexp - the way "qr/ test /" in Perl would do, so that
> it doesn't have to re-compile it on every iteration.

Not necessary in Ruby: regexp literals are treated specially and are
not recompiled.  Usually it's faster to do

io.each do |line|
  if line =~ /foo/
  end
end

than

rx = /foo/

io.each do |line|
  if line =~ rx
  end
end

If there is dynamic content, use /o:

input = gets

io.each do |line|
  if line =~ /foo:#{input}/o
  end
end

Kind regards

robert

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