Beer Song

Clojure

(ns beer-song
  (:require [clojure.string :as str]))

(defn- generalised-verse [num]
  (format
   "%s bottles of beer on the wall, %s bottles of beer.\nTake one down and pass it around, %s bottles of beer on the wall.\n"
   num
   num
   (dec num)))

(defn verse
  "Returns the nth verse of the song."
  ([num]
   (case num
     0 "No more bottles of beer on the wall, no more bottles of beer.\nGo to the store and buy some more, 99 bottles of beer on the wall.\n"
     1 "1 bottle of beer on the wall, 1 bottle of beer.\nTake it down and pass it around, no more bottles of beer on the wall.\n"
     2 "2 bottles of beer on the wall, 2 bottles of beer.\nTake one down and pass it around, 1 bottle of beer on the wall.\n"
     (generalised-verse num))))

(defn sing
  "Given a start and an optional end, returns all verses in this interval. If
  end is not given, the whole song from start is sung."
  ([start] (sing start 0))
  ([start end] (str/join "\n"
                         (->>
                          (range start (dec end) -1)
                          (map verse)))))

Elixir

Other Elixir solutions.

defmodule BeerSong do
  @doc """
  Get a single verse of the beer song
  """
  @spec verse(integer) :: String.t()
  def verse(number) do
    case number do
      0 ->
        "No more bottles of beer on the wall, no more bottles of beer.\nGo to the store and buy some more, 99 bottles of beer on the wall.\n"

      1 ->
        "1 bottle of beer on the wall, 1 bottle of beer.\nTake it down and pass it around, no more bottles of beer on the wall.\n"

      2 ->
        "2 bottles of beer on the wall, 2 bottles of beer.\nTake one down and pass it around, 1 bottle of beer on the wall.\n"

      number ->
        "#{number} bottles of beer on the wall, #{number} bottles of beer.\nTake one down and pass it around, #{
          number - 1
        } bottles of beer on the wall.\n"
    end
  end

  @doc """
  Get the entire beer song for a given range of numbers of bottles.
  """
  @spec lyrics(Range.t()) :: String.t()
  def lyrics(range \\ 99..0) do
    range
    |> Enum.map(&verse(&1))
    |> Enum.join("\n")
  end
end