Ruby version for http://qiita.com/kuroyakov/items/0b2076df3619e20725e6

map_filter_reduce.rb

require 'benchmark'

def with_sum
  (0..9_999_999)
    .map { |n| n * 2 }
    .select { |n| n % 3 == 0 }
    .sum
end

def with_inject
  (0..9_999_999)
    .map { |n| n * 2 }
    .select { |n| n % 3 == 0 }
    .inject(:+)
end

Benchmark.bm 10 do |r|
  r.report 'with sum' do
    with_sum
  end
  r.report 'with inject' do
    with_inject
  end
end

# Ruby 2.4.1
#                  user     system      total        real
# with sum     1.170000   0.030000   1.200000 (  1.199294)
# with inject  1.190000   0.050000   1.240000 (  1.243078)