A program that prints out the numbers 1 to 100 (inclusive). If the number is divisible by 3, print Crackle instead of the number. If it's divisible by 5, print Pop. If it's divisible by both 3 and 5, print CracklePop.

multiple-of-3-or-5-or-both.ex

defmodule Math do
  def map_number(number) do
    case { rem(number,3), rem(number,5) } do
      { 0, 0 } ->                  
       "CradlePop"              
      { 0, _ } ->                 
       "Cradle"                 
      { _, 0 } ->                 
       "Pop" 
      { _, _ } ->
       number
    end
  end
end

1..100 |> Enum.map(&Math.map_number/1) |> Enum.each(&IO.puts/1)