Let’s start today’s post with a weird Ruby benchmark: require "benchmark/ips" class Foo def initialize forward forward ? go_forward : go_backward end ivars = ("a".."zz").map { |name| "@#{name} = 5" } # define the go_forward method eval "def go_forward; #{ivars.join("; ")} end" # define the go_backward method eval "def go_backward; #{ivars.reverse.join("; ")} end" end # Heat Foo.new true Foo.new false Benchmark.ips do |x| x.report("backward") { 5000.times { Foo.new false } } x.report("forward") { 5000.times { Foo.new true } } end This code defines a class that sets a bunch of instance variables, but the order that the instance variables are set depends on the parameter passed in to the constructor. When we pass true, it defines instance variables “a” through “zz”, and when we pass false it defines them “zz” through “a”.