functions_2.ex

defmodule D do

  def add(a, b, c), do: a + b + c  # Arity 3
  def add(b, b), do: 3 * b         # Pattern matching
  def add("i", b), do: "#{b}i"     # Pattern matching
  def add(a, _), do: a + a         # Strange default, but we'll go with it
  def add(_), do: IO.puts "Can't add one number, silly"

end

D.add(1, 2, 3)
# => 6
D.add(5, 5)
# => 15
D.add("i", 10)
# => 10i
D.add(3, 4)
# => 6
D.add(10)
# => "Can't add one number, silly"