Adzz

defmodule Perimeter do
  def calculate(shape) do
    case shape do
      %Square{side: side} -> side * 4
      %Circle{radius: radius} -> radius * 2 * 3.14
    end
  end
end

Perimeter.calculate(%Square{side: 10}) #=> 40

Adzz

Shape.area(%Square{side: 10}) #=> 100

Adzz

# Make some shapes
defmodule Square do
  defstruct [:side]
end

defmodule Circle do
  defstruct [:radius]
end

Adzz

defprotocol Perimeter do
  def calculate(shape)
end

defimpl Perimeter, for: Square do
  def calculate(square) do
    square.side * 4
  end
end

Adzz

defmodule Square do
  defstruct [:side]
end

defmodule Circle do
  defstruct [:radius]
end

defprotocol Area do

Adzz

defmodule Square do
  defstruct [:side]
end

defmodule Circle do
  defstruct [:radius]
end

defprotocol Area do

Adzz

Shape.calculate(:area, %Square{side: 10})

Adzz

defmodule Square do
  defstruct [:side]
end

defmodule Area do
  defstruct []
end

defprotocol Shape do
  def calculate(calculation, shape)

Adzz

defmodule Circle do
  defstruct [:radius]
end

defimpl AreaProtocol, for: Circle do
  def calculate(%Circle{radius: radius}) do
    3.14 * radius * radius
  end
end

Adzz

defmodule Perimeter do
  defstruct []
end

defprotocol PerimeterProtocol do
  def calculate(shape)
end

defimpl Shape, for: Perimeter do
  def calculate(%Perimeter{}, shape) do