require 'benchmark/ips'


Benchmark.ips do |x|
  x.report('mutating and fast') do
    result = ''
    1.upto(50) do |x|
      result << x
    end
  end

  x.report('pure, but slow') do
    1.upto(50).reduce('') {|memo, elem| memo + elem.to_s}
  end

  x.compare!
end
# Warming up --------------------------------------
#    mutating and fast    18.469k i/100ms
#       pure, but slow     6.683k i/100ms
# Calculating -------------------------------------
#    mutating and fast    190.909k (± 3.4%) i/s -    960.388k in   5.036743s
#       pure, but slow     68.436k (± 2.3%) i/s -    347.516k in   5.080727s

# Comparison:
#    mutating and fast:   190908.6 i/s
#       pure, but slow:    68435.5 i/s - 2.79x  slower