Ruby - Array.join versus String Concatenation (Efficiency)

Question

I recall getting a scolding for concatenating Strings in Python once upon a time. I was told that it is more efficient to create an List of Strings in Python and join them later

Answer 1

Funny, benchmarking gives surprising results (unless I'm doing something wrong):

require 'benchmark'

N = 1_000_000
Benchmark.bm(20) do |rep|

  rep.report('+') do
    N.times do
      res = 'foo' + 'bar' + 'baz'
    end
  end

  rep.report('join') do
    N.times do
      res = ['foo', 'bar', 'baz'].join
    end
  end

  rep.report('<<') do
    N.times do
      res = 'foo' << 'bar' << 'baz'
    end
  end
end

gives

jablan@poneti:~/dev/rb$ ruby concat.rb 
                          user     system      total        real
+                     1.760000   0.000000   1.760000 (  1.791334)
join                  2.410000   0.000000   2.410000 (  2.412974)
<<                    1.380000   0.000000   1.380000 (  1.376663)

join turns out to be the slowest. It might have to do with creating the array, but that's what you would have to do anyway.

Oh BTW,

jablan@poneti:~/dev/rb$ ruby -v
ruby 1.9.1p378 (2010-01-10 revision 26273) [i486-linux]