equality.ex

defmodule Equality do
  @tests [
    0,
    1,
    -1,
    2,
    -2,
    10,
    -10,
    3,
    5,
    8,
    13,
    21,
    -3,
    -5,
    -8,
    -13,
    -21,
    17,
    19,
    23,
    29,
    127,
    128,
    -127,
    -128,
    254,
    255,
    256,
    384,
    1_234_567_890,
    -254,
    -255,
    -256,
    -384,
    -1_234_567_890,
    987_654_321,
    -987_654_321
  ]
  def benchmark do
    Benchee.run(%{
      "primitive" => fn -> test!(&primitive/2) end,
      "subtract" => fn -> test!(&subtract/2) end,
      "pattern match" => fn -> test!(&pattern_match/2) end,
      "match exception" => fn -> test!(&match_exception/2) end,
      "exception" => fn -> test!(&exception/2) end
    })
  end

  def test!(func) do
    Enum.each(@tests, fn a ->
      Enum.each(@tests, fn b ->
        func.(a, b)
      end)
    end)
  end

  def primitive(a, b) do
    a == b
  end

  def subtract(a, b) do
    0 == a - b
  end

  def pattern_match(a, b) do
    case a do
      ^b -> true
      _ -> false
    end
  end

  def match_exception(a, b) do
    try do
      ^a = b
      true
    rescue
      MatchError -> false
    end
  end

  def exception(a, b) do
    try do
      1 / (a - b)
      false
    rescue
      ArithmeticError -> true
    end
  end
end