next_to_last.exs

list = Enum.to_list(1..100_000)

Benchee.init(%{time: 3})
|> Benchee.benchmark("Enum.at", fn -> Enum.at(list, length(list) - 2) end)
|> Benchee.benchmark(
  "revers + pattern matching",
  fn ->
    [_, next_to_last | _] = Enum.reverse(list)
    next_to_last
  end
)
|> Benchee.statistics
|> Benchee.Formatters.Console.format
|> IO.puts

# Results

Benchmarking Enum.at...
Benchmarking revers + pattern matching...

Name                          ips            average        deviation      median
revers + pattern matching     2264.76        441.55μs       (±74.31%)      257.00μs
Enum.at                       962.23         1039.25μs      (±15.16%)      980.00μs

Comparison:
revers + pattern matching     2264.76
Enum.at                       962.23          - 2.35x slower