Can you chain maps and eat cake too?

gistfile1.txt

Allocations -------------------------------------
                null       0/0  alloc/ret        0/0  strings/ret
        mega no work       1/0  alloc/ret        0/0  strings/ret
      mega w/ locals  1446/114  alloc/ret      50/50  strings/ret
             chained    1334/0  alloc/ret       50/0  strings/ret
        lazy chained    2102/0  alloc/ret       50/0  strings/ret
Warming up --------------------------------------
                null   151.895k i/100ms
        mega no work     6.384k i/100ms
      mega w/ locals   135.000  i/100ms
             chained   133.000  i/100ms
        lazy chained   105.000  i/100ms
Calculating -------------------------------------
                null     10.550M (± 6.3%) i/s -     52.556M
        mega no work     67.528k (± 5.1%) i/s -    338.352k
      mega w/ locals      1.403k (± 3.4%) i/s -      7.020k
             chained      1.362k (± 2.8%) i/s -      6.916k
        lazy chained      1.040k (± 5.0%) i/s -      5.250k

maps.rb

require "benchmark/ipsa"
require "digest/md5"

text = File.read("/etc/passwd")
lines = text.split

# sillysum obfuscates a file by:
#
# - rot13'ing each line
# - upcasing each line
# - calculating the MD5 of each rot13'd line
# - concatenating all the MD5s
#
# It is really silly.

ROT13_INPUT = 'A-Za-z'
ROT13_OUTPUT = 'N-ZA-Mn-za-m'
Benchmark.ipsa do |x|
  x.report("null") do
  end

  x.report("mega no work") do
    lines.map {}
  end

  x.report("mega w/ locals") do
    lines.map { |l|
      rot13 = l.tr(ROT13_INPUT, ROT13_OUTPUT)
      upcase = rot13.upcase

      Digest::MD5.hexdigest(upcase)
    }.join("")
  end

  x.report("chained") do
    lines.
      map { |line| line.tr(ROT13_INPUT, ROT13_OUTPUT) }.
      map { |line| line.upcase }.
      map { |line| Digest::MD5.hexdigest(line) }.
      join("")
  end

  x.report("lazy chained") do
    lines.lazy.
      map { |line| line.tr(ROT13_INPUT, ROT13_OUTPUT) }.
      map { |line| line.upcase }.
      map { |line| Digest::MD5.hexdigest(line) }.
      to_a.
      join("")
  end
end