From: Joel VanderWerf <vjoel@...>
Date: 2008-03-07T07:02:22+09:00
Subject: Re: duplicating characters in a string

Rodrigo Bermejo wrote:
> "abc".gsub(/./) { |x| x * 2 }

That's the most elegant way to refer to captures, but if speed matters:

"abc".gsub(/(.)/, "\\1\\1")

The "\\1" is always easy to mess up, which is why I generally prefer the 
block form.

It's only about a factor of two faster, according to the following, but 
that matters sometimes.

require 'benchmark'

Benchmark.bmbm do |b|
   s = "abc" * 1_000_000
   re = /(.)/

   b.report("s.gsub(re){...}") do
     s.gsub(re) { |x| x * 2 }
   end

   b.report("s.gsub(re,...)") do
     s.gsub(re, "\\1\\1")
   end
end

__END__

Rehearsal ---------------------------------------------------
s.gsub(re){...}   5.970000   0.000000   5.970000 (  6.009089)
s.gsub(re,...)    2.900000   0.060000   2.960000 (  3.148006)
------------------------------------------ total: 8.930000sec

                       user     system      total        real
s.gsub(re){...}   5.760000   0.010000   5.770000 (  5.925049)
s.gsub(re,...)    2.800000   0.060000   2.860000 (  2.914432)

-- 
       vjoel : Joel VanderWerf : path berkeley edu : 510 665 3407