arrow_def.rb

require 'benchmark/ips'

Benchmark.ips do |x|
  ary = []
  
  x.report(:a) {
    10_000.times do |num|
      ary << "#{num} #{num * 2} #{num * 3}"
    end
  }
  
  x.report(:b){
    calc_num = -> (n) { "#{n} #{n * 2} #{n * 3}" }
    10_000.times do |num|
      ary << calc_num.call(num)
    end
  }

  x.compare!
end 

comparison.txt

Warming up --------------------------------------
                   a    13.000  i/100ms
                   b    10.000  i/100ms
Calculating -------------------------------------
                   a    109.073  (±22.9%) i/s -    468.000  in   5.057635s
                   b     81.887  (±41.5%) i/s -    300.000  in   5.174320s

Comparison:
                   a:      109.1 i/s
                   b:       81.9 i/s - same-ish: difference falls within error