translate_with_else

case_bench.exs

defmodule CaseBench do
  use Benchfella

  defp ok_or_error_with_atom do
    Stream.cycle([:ok, {:error, :err}])
    |> Enum.take(1000)
  end

  defp ok_or_error_with_string do
    Stream.cycle([:ok, {:error, "err"}])
    |> Enum.take(1000)
  end

  bench "case with else clauses" do
    for x <- ok_or_error_with_atom(),
        y <- ok_or_error_with_string() do
        case x do
          :ok ->
            case y do
              :ok -> :ok
              {:error, error} when is_atom(error) -> :error
              {:error, _error} -> :error
            end
          {:error, error} when is_atom(error) -> :error
          {:error, _error} -> :error
        end
      end
  end

  bench "two cases" do
    for x <- ok_or_error_with_atom(),
        y <- ok_or_error_with_string() do
      {branch, result} = case x do
        :ok ->
          case y do
            :ok -> {:do, :ok}
            other -> {:else, other}
          end
        other -> {:else, other}
      end
      case branch do
        :do -> result
        :else ->
          case result do
            {:error, error} when is_atom(error) -> :error
            {:error, _error} -> :error
          end
      end
    end
  end
end

result

Settings:
  duration:      1.0 s

## CaseBench
[23:36:41] 1/2: case with else clauses
[23:36:43] 2/2: two cases

Finished in 3.46 seconds

## CaseBench
benchmark name          iterations   average time 
two cases                       10   148161.50 µs/op
case with else clauses          10   151157.40 µs/op