String concatenation vs. interpolation in Ruby

Question

I am just starting to learn Ruby (first time programming), and have a basic syntactical question with regards to variables, and various ways of writing code.

Chris

Answer 1

If you are using a string as a buffer, I found that using concatenation (String#concat) to be faster.

require 'benchmark/ips'

puts "Ruby #{RUBY_VERSION} at #{Time.now}"
puts

firstname = 'soundarapandian'
middlename = 'rathinasamy'
lastname = 'arumugam'

Benchmark.ips do |x|
    x.report("String\#<<") do |i|
        buffer = String.new

        while (i -= 1) > 0
            buffer << 'Mr. ' << firstname << middlename << lastname << ' aka soundar'
        end
    end

    x.report("String interpolate") do |i|
        buffer = String.new

        while (i -= 1) > 0
            buffer << "Mr. #{firstname} #{middlename} #{lastname} aka soundar"
        end
    end

    x.compare!
end

Results:

Ruby 2.3.1 at 2016-11-15 15:03:57 +1300

Warming up --------------------------------------
           String#<<   230.615k i/100ms
  String interpolate   234.274k i/100ms
Calculating -------------------------------------
           String#<<      2.345M (± 7.2%) i/s -     11.761M in   5.041164s
  String interpolate      1.242M (± 5.4%) i/s -      6.325M in   5.108324s

Comparison:
           String#<<:  2344530.4 i/s
  String interpolate:  1241784.9 i/s - 1.89x  slower

At a guess, I'd say that interpolation generates a temporary string which is why it's slower.