FizzBuzz. Try elm there: http://elm-lang.org/try

fizz_buzz.ex

defmodule FizzBuzz do
  defp fizz({i, r} = line) do
    if rem(i, 3) == 0 do
      {i, r <> "Fizz"}
    else
      line
    end
  end

  defp buzz({i, r} = line) do
    if rem(i, 5) == 0 do
      {i, r <> "Buzz"}
    else
      line
    end
  end

  defp number({i, r} = line) do
    if r === "" do
      {i, Integer.to_string i}
    else
      line
    end
  end

  def fizz_buzz(list) do
    list
    |> Enum.map(fn i -> {i, ""} end)
    |> Enum.map(&fizz/1)
    |> Enum.map(&buzz/1)
    |> Enum.map(&number/1)
    |> Enum.map(fn {_, s} -> s end)
  end
end

1..100
|> FizzBuzz.fizz_buzz
|> IO.inspect

FizzBuzz.elm

import Html exposing (ul, li, text)


fizzBuzz list =
    let
        fizz ( i, r ) =
            if i % 3 == 0 then
                ( i, r ++ "Fizz" )
            else
                ( i, r )

        buzz ( i, r ) =
            if i % 5 == 0 then
                ( i, r ++ "Buzz" )
            else
                ( i, r )

        number ( i, r ) =
            if String.isEmpty r then
                ( i, toString i )
            else
                ( i, r )
    in
        list
            |> List.map (\i -> ( i, "" ))
            |> List.map fizz
            |> List.map buzz
            |> List.map number
            |> List.map Tuple.second


main =
    let
        lines =
            List.range 1 100
                |> fizzBuzz
                |> List.map (\i -> li [] [ text i ])
    in
        ul [] lines