Cracklepop

cracklepop.ex

defmodule Cracklepop do
  @moduledoc """
  Returns a list of number strings, 1 to 100 (inclusive).
  If the number is divisible by 3, prints 'Crackle' instead of the number.
  If it's divisible by 5, prints 'Pop' instead of the number.
  If it's divisible by both 3 and 5, prints 'CracklePop' instead of the number.

  DEV NOTES: I've decided to use strings for all values for consistency, and
  presumed "printing" means it's valid to return a list of strings to the console
  using iex instead of explicitly using IO.puts/1 for each value. Hope this is ok!
  """

  @doc """
  Entrypoint for the main cracklepop function.

      iex> length(Cracklepop.cracklepop())
      100
  """
  @spec cracklepop() :: [String.t()]
  def cracklepop do
    Enum.map(1..100, &cracklepop/1)
  end

  @doc """
  Converts an integer to the required cracklepop string.

      iex> Cracklepop.cracklepop(3)
      "Crackle"
      iex> Cracklepop.cracklepop(10)
      "Pop"
      iex> Cracklepop.cracklepop(15)
      "CracklePop"
      iex> Cracklepop.cracklepop(11)
      "11"
  """
  @spec cracklepop(integer()) :: String.t()
  def cracklepop(n) when rem(n, 3) == 0 and rem(n, 5) == 0, do: "CracklePop"
  def cracklepop(n) when rem(n, 3) == 0, do: "Crackle"
  def cracklepop(n) when rem(n, 5) == 0, do: "Pop"
  def cracklepop(n), do: Integer.to_string(n)
end