geom.ex

defmodule Etudes.Geom do
  @spec area(atom(), number(), number()) :: number()
  def area(:rectangle, x, y) when x > 0 and y > 0 do
    x * y
  end

  def area(:triangle, base, height) when base > 0 and height > 0 do
    (base * height) / 2.0
  end

  def area(:ellipse, x, y) when x > 0 and y > 0 do
    :math.pi * x * y
  end

  @spec sum(number(), number(), number()) :: number()
  def sum(x \\ 1, y \\ 1, z \\ 1), do: x + y + z
end

defmodule GeomTest do
  use ExUnit.Case
  doctest Etudes.Geom
  alias Etudes.Geom

  test "calculate area" do
    assert Geom.area(:rectangle, 2, 4)           == 8
    assert Geom.area(:triangle, 4, 2)            == 4.0
    assert Geom.area(:ellipse, 2, 4)             == 25.132741228718345
  end

  test "calculate a sum of up to 3" do
    assert Geom.sum(2)       == 4
    assert Geom.sum(2, 2)    == 5
    assert Geom.sum(2, 2, 2) == 6
  end
end