lazy.rb

# Enumerator#lazy is very slow and should only be used when iterating over large/infinite collections
# where you know you are going to get your results quite early in the iteration.

require 'benchmark/ips'

Benchmark.ips do |r|  
  r.report("map") do
    (0..50).map{ |i| 'lol' if i.even? }
  end
 
  r.report("lazy+map") do
    (0..50).lazy.map { |i| 'lol' if i.even? }.to_a
  end
end

Calculating -------------------------------------
            map           7726 i/100ms
            lazy+map      2451 i/100ms
-------------------------------------------------
            map         87178.8 (±2.6%) i/s -     440382 in   5.055076s
            lazy+map    27059.9 (±2.7%) i/s -     137256 in   5.076049s