Count ways to break a dollar using Elixir

break_dollar.exs

defmodule Money do

  @silver_dollar 100
  @half_dollar    50
  @quarter        25
  @dime           10
  @nickel          5
  @penny           1
  def all_coins, do: [@silver_dollar, @half_dollar, @quarter, @dime, @nickel, @penny]

  def break(amount, coins), do: do_break(amount, coins)

  defp do_break(     _, [@penny]              ), do: 1  
  defp do_break(amount, [coin | smaller_coins])  do
    0..div(amount, coin)
    |> Enum.reduce(0, fn(coin_count, sum) ->
      remaining_amount = amount - coin * coin_count
      sum + do_break(remaining_amount, smaller_coins)
    end)
  end

end

# Determine how many ways there are to break a dollar.
IO.inspect Money.break(100, Money.all_coins)