Recursion

Recursion

Elixir uses recursion instead of traditional loops. A recursive function calls itself with a smaller problem.

defmodule Math do
  def factorial(0), do: 1
  def factorial(n), do: n * factorial(n - 1)
end

IO.puts(Math.factorial(5))   # 120

The first clause matches 0 (base case), the second matches any other value.

Sum of a List

defmodule MyList do
  def sum([]), do: 0
  def sum([head | tail]), do: head + sum(tail)
end

IO.puts(MyList.sum([1, 2, 3, 4, 5]))   # 15

Your Turn

Implement:

1. Math.factorial(5) → 120
2. MyList.sum([1, 2, 3, 4, 5]) → 15