geometry.ex

module Geometry do
  @moduledoc """
  Calculates area of different shapes
  """
  
  @doc """
  Some other comment
  """
  def area({:rectangle, width, height}) do:  width * height
  def area({:square, side}) do:  side * side
  def area({:circle, radius}) do:  3.14159 * radius * radius
end

geometry.rb

class Circle
  attr_accessor :radius
  
  def initialize(radius)
    @radius = radius
  end
  
  def area
    Math::PI * radius**2
  end
end

class Square
  attr_accessor :side
  
  def initialize(side)
    @side = side
  end
  
  def area
    side**2
  end
end

class Rectangle
  attr_accessor :width, :height
  
  def initialize(width, height)
    @width = width
    @height = height
  end
  
  def area
    width * height
  end
end