fizzbuzz.ex

defmodule FizzBuzz do
  def fizzbuzz(a) when rem(a, 3) == 0 and rem(a, 5) == 0, do: "FizzBuzz"
  def fizzbuzz(a) when rem(a, 3) == 0, do: "Fizz"
  def fizzbuzz(a) when rem(a, 5) == 0, do: "Buzz"
  def fizzbuzz(a), do: a
end

1..100 |> Enum.map(&FizzBuzz.fizzbuzz/1) |> Enum.each(&IO.puts/1)

fizzbuzz2.ex

defmodule FizzBuzz do
  defp whichfizz(0, 0, _), do: "FizzBuzz"
  defp whichfizz(0, _, _), do: "Fizz"
  defp whichfizz(_, 0, _), do: "Buzz"
  defp whichfizz(_, _, n), do: n
  
  def fizzbuzz(n), do: whichfizz(rem(n, 3), rem(n, 5), n)
end

1..100 |> Enum.map(&FizzBuzz.fizzbuzz/1) |> Enum.each(&IO.puts/1)