Process

• create a file named hollow_pyramid.ex
• write the code

hollow_pyramid = fn number ->
  for i <- 1..number do
    # for printing spaces

    spaces =
      for j when j <= number - i <- 1..number do
        " "
      end

    # for printing star
    star_number = 2 * i - 2

    star =
      for k <- 0..star_number do
        if i == 1 || i == number do
          "*"
        else
          if k == 0 || k == star_number do
            "*"
          else
            " "
          end
        end
      end

    spaces ++ star
  end
  |> Enum.into("", fn string ->
    string = Enum.join(string)
    "#{string}\n"
  end)
end

IO.puts(hollow_pyramid.(10))
IO.puts(hollow_pyramid.(5))

• run elixir hollow_pyramid.ex

Result

         *
        * *
       *   *
      *     *
     *       *
    *         *
   *           *
  *             *
 *               *
*******************

    *
   * *
  *   *
 *     *
*********

Happy Coding!