davearonson's solution to Beer Song on the Elixir track

Instructions

Test suite

Solution

Note:

This solution was written on an old version of Exercism. The tests below might not correspond to the solution code, and the exercise may have changed since this code was written.

Recite the lyrics to that beloved classic, that field-trip favorite: 99 Bottles of Beer on the Wall.

Note that not all verses are identical.

99 bottles of beer on the wall, 99 bottles of beer.
Take one down and pass it around, 98 bottles of beer on the wall.

98 bottles of beer on the wall, 98 bottles of beer.
Take one down and pass it around, 97 bottles of beer on the wall.

97 bottles of beer on the wall, 97 bottles of beer.
Take one down and pass it around, 96 bottles of beer on the wall.

96 bottles of beer on the wall, 96 bottles of beer.
Take one down and pass it around, 95 bottles of beer on the wall.

95 bottles of beer on the wall, 95 bottles of beer.
Take one down and pass it around, 94 bottles of beer on the wall.

94 bottles of beer on the wall, 94 bottles of beer.
Take one down and pass it around, 93 bottles of beer on the wall.

93 bottles of beer on the wall, 93 bottles of beer.
Take one down and pass it around, 92 bottles of beer on the wall.

92 bottles of beer on the wall, 92 bottles of beer.
Take one down and pass it around, 91 bottles of beer on the wall.

91 bottles of beer on the wall, 91 bottles of beer.
Take one down and pass it around, 90 bottles of beer on the wall.

90 bottles of beer on the wall, 90 bottles of beer.
Take one down and pass it around, 89 bottles of beer on the wall.

89 bottles of beer on the wall, 89 bottles of beer.
Take one down and pass it around, 88 bottles of beer on the wall.

88 bottles of beer on the wall, 88 bottles of beer.
Take one down and pass it around, 87 bottles of beer on the wall.

87 bottles of beer on the wall, 87 bottles of beer.
Take one down and pass it around, 86 bottles of beer on the wall.

86 bottles of beer on the wall, 86 bottles of beer.
Take one down and pass it around, 85 bottles of beer on the wall.

85 bottles of beer on the wall, 85 bottles of beer.
Take one down and pass it around, 84 bottles of beer on the wall.

84 bottles of beer on the wall, 84 bottles of beer.
Take one down and pass it around, 83 bottles of beer on the wall.

83 bottles of beer on the wall, 83 bottles of beer.
Take one down and pass it around, 82 bottles of beer on the wall.

82 bottles of beer on the wall, 82 bottles of beer.
Take one down and pass it around, 81 bottles of beer on the wall.

81 bottles of beer on the wall, 81 bottles of beer.
Take one down and pass it around, 80 bottles of beer on the wall.

80 bottles of beer on the wall, 80 bottles of beer.
Take one down and pass it around, 79 bottles of beer on the wall.

79 bottles of beer on the wall, 79 bottles of beer.
Take one down and pass it around, 78 bottles of beer on the wall.

78 bottles of beer on the wall, 78 bottles of beer.
Take one down and pass it around, 77 bottles of beer on the wall.

77 bottles of beer on the wall, 77 bottles of beer.
Take one down and pass it around, 76 bottles of beer on the wall.

76 bottles of beer on the wall, 76 bottles of beer.
Take one down and pass it around, 75 bottles of beer on the wall.

75 bottles of beer on the wall, 75 bottles of beer.
Take one down and pass it around, 74 bottles of beer on the wall.

74 bottles of beer on the wall, 74 bottles of beer.
Take one down and pass it around, 73 bottles of beer on the wall.

73 bottles of beer on the wall, 73 bottles of beer.
Take one down and pass it around, 72 bottles of beer on the wall.

72 bottles of beer on the wall, 72 bottles of beer.
Take one down and pass it around, 71 bottles of beer on the wall.

71 bottles of beer on the wall, 71 bottles of beer.
Take one down and pass it around, 70 bottles of beer on the wall.

70 bottles of beer on the wall, 70 bottles of beer.
Take one down and pass it around, 69 bottles of beer on the wall.

69 bottles of beer on the wall, 69 bottles of beer.
Take one down and pass it around, 68 bottles of beer on the wall.

68 bottles of beer on the wall, 68 bottles of beer.
Take one down and pass it around, 67 bottles of beer on the wall.

67 bottles of beer on the wall, 67 bottles of beer.
Take one down and pass it around, 66 bottles of beer on the wall.

66 bottles of beer on the wall, 66 bottles of beer.
Take one down and pass it around, 65 bottles of beer on the wall.

65 bottles of beer on the wall, 65 bottles of beer.
Take one down and pass it around, 64 bottles of beer on the wall.

64 bottles of beer on the wall, 64 bottles of beer.
Take one down and pass it around, 63 bottles of beer on the wall.

63 bottles of beer on the wall, 63 bottles of beer.
Take one down and pass it around, 62 bottles of beer on the wall.

62 bottles of beer on the wall, 62 bottles of beer.
Take one down and pass it around, 61 bottles of beer on the wall.

61 bottles of beer on the wall, 61 bottles of beer.
Take one down and pass it around, 60 bottles of beer on the wall.

60 bottles of beer on the wall, 60 bottles of beer.
Take one down and pass it around, 59 bottles of beer on the wall.

59 bottles of beer on the wall, 59 bottles of beer.
Take one down and pass it around, 58 bottles of beer on the wall.

58 bottles of beer on the wall, 58 bottles of beer.
Take one down and pass it around, 57 bottles of beer on the wall.

57 bottles of beer on the wall, 57 bottles of beer.
Take one down and pass it around, 56 bottles of beer on the wall.

56 bottles of beer on the wall, 56 bottles of beer.
Take one down and pass it around, 55 bottles of beer on the wall.

55 bottles of beer on the wall, 55 bottles of beer.
Take one down and pass it around, 54 bottles of beer on the wall.

54 bottles of beer on the wall, 54 bottles of beer.
Take one down and pass it around, 53 bottles of beer on the wall.

53 bottles of beer on the wall, 53 bottles of beer.
Take one down and pass it around, 52 bottles of beer on the wall.

52 bottles of beer on the wall, 52 bottles of beer.
Take one down and pass it around, 51 bottles of beer on the wall.

51 bottles of beer on the wall, 51 bottles of beer.
Take one down and pass it around, 50 bottles of beer on the wall.

50 bottles of beer on the wall, 50 bottles of beer.
Take one down and pass it around, 49 bottles of beer on the wall.

49 bottles of beer on the wall, 49 bottles of beer.
Take one down and pass it around, 48 bottles of beer on the wall.

48 bottles of beer on the wall, 48 bottles of beer.
Take one down and pass it around, 47 bottles of beer on the wall.

47 bottles of beer on the wall, 47 bottles of beer.
Take one down and pass it around, 46 bottles of beer on the wall.

46 bottles of beer on the wall, 46 bottles of beer.
Take one down and pass it around, 45 bottles of beer on the wall.

45 bottles of beer on the wall, 45 bottles of beer.
Take one down and pass it around, 44 bottles of beer on the wall.

44 bottles of beer on the wall, 44 bottles of beer.
Take one down and pass it around, 43 bottles of beer on the wall.

43 bottles of beer on the wall, 43 bottles of beer.
Take one down and pass it around, 42 bottles of beer on the wall.

42 bottles of beer on the wall, 42 bottles of beer.
Take one down and pass it around, 41 bottles of beer on the wall.

41 bottles of beer on the wall, 41 bottles of beer.
Take one down and pass it around, 40 bottles of beer on the wall.

40 bottles of beer on the wall, 40 bottles of beer.
Take one down and pass it around, 39 bottles of beer on the wall.

39 bottles of beer on the wall, 39 bottles of beer.
Take one down and pass it around, 38 bottles of beer on the wall.

38 bottles of beer on the wall, 38 bottles of beer.
Take one down and pass it around, 37 bottles of beer on the wall.

37 bottles of beer on the wall, 37 bottles of beer.
Take one down and pass it around, 36 bottles of beer on the wall.

36 bottles of beer on the wall, 36 bottles of beer.
Take one down and pass it around, 35 bottles of beer on the wall.

35 bottles of beer on the wall, 35 bottles of beer.
Take one down and pass it around, 34 bottles of beer on the wall.

34 bottles of beer on the wall, 34 bottles of beer.
Take one down and pass it around, 33 bottles of beer on the wall.

33 bottles of beer on the wall, 33 bottles of beer.
Take one down and pass it around, 32 bottles of beer on the wall.

32 bottles of beer on the wall, 32 bottles of beer.
Take one down and pass it around, 31 bottles of beer on the wall.

31 bottles of beer on the wall, 31 bottles of beer.
Take one down and pass it around, 30 bottles of beer on the wall.

30 bottles of beer on the wall, 30 bottles of beer.
Take one down and pass it around, 29 bottles of beer on the wall.

29 bottles of beer on the wall, 29 bottles of beer.
Take one down and pass it around, 28 bottles of beer on the wall.

28 bottles of beer on the wall, 28 bottles of beer.
Take one down and pass it around, 27 bottles of beer on the wall.

27 bottles of beer on the wall, 27 bottles of beer.
Take one down and pass it around, 26 bottles of beer on the wall.

26 bottles of beer on the wall, 26 bottles of beer.
Take one down and pass it around, 25 bottles of beer on the wall.

25 bottles of beer on the wall, 25 bottles of beer.
Take one down and pass it around, 24 bottles of beer on the wall.

24 bottles of beer on the wall, 24 bottles of beer.
Take one down and pass it around, 23 bottles of beer on the wall.

23 bottles of beer on the wall, 23 bottles of beer.
Take one down and pass it around, 22 bottles of beer on the wall.

22 bottles of beer on the wall, 22 bottles of beer.
Take one down and pass it around, 21 bottles of beer on the wall.

21 bottles of beer on the wall, 21 bottles of beer.
Take one down and pass it around, 20 bottles of beer on the wall.

20 bottles of beer on the wall, 20 bottles of beer.
Take one down and pass it around, 19 bottles of beer on the wall.

19 bottles of beer on the wall, 19 bottles of beer.
Take one down and pass it around, 18 bottles of beer on the wall.

18 bottles of beer on the wall, 18 bottles of beer.
Take one down and pass it around, 17 bottles of beer on the wall.

17 bottles of beer on the wall, 17 bottles of beer.
Take one down and pass it around, 16 bottles of beer on the wall.

16 bottles of beer on the wall, 16 bottles of beer.
Take one down and pass it around, 15 bottles of beer on the wall.

15 bottles of beer on the wall, 15 bottles of beer.
Take one down and pass it around, 14 bottles of beer on the wall.

14 bottles of beer on the wall, 14 bottles of beer.
Take one down and pass it around, 13 bottles of beer on the wall.

13 bottles of beer on the wall, 13 bottles of beer.
Take one down and pass it around, 12 bottles of beer on the wall.

12 bottles of beer on the wall, 12 bottles of beer.
Take one down and pass it around, 11 bottles of beer on the wall.

11 bottles of beer on the wall, 11 bottles of beer.
Take one down and pass it around, 10 bottles of beer on the wall.

10 bottles of beer on the wall, 10 bottles of beer.
Take one down and pass it around, 9 bottles of beer on the wall.

9 bottles of beer on the wall, 9 bottles of beer.
Take one down and pass it around, 8 bottles of beer on the wall.

8 bottles of beer on the wall, 8 bottles of beer.
Take one down and pass it around, 7 bottles of beer on the wall.

7 bottles of beer on the wall, 7 bottles of beer.
Take one down and pass it around, 6 bottles of beer on the wall.

6 bottles of beer on the wall, 6 bottles of beer.
Take one down and pass it around, 5 bottles of beer on the wall.

5 bottles of beer on the wall, 5 bottles of beer.
Take one down and pass it around, 4 bottles of beer on the wall.

4 bottles of beer on the wall, 4 bottles of beer.
Take one down and pass it around, 3 bottles of beer on the wall.

3 bottles of beer on the wall, 3 bottles of beer.
Take one down and pass it around, 2 bottles of beer on the wall.

2 bottles of beer on the wall, 2 bottles of beer.
Take one down and pass it around, 1 bottle of beer on the wall.

1 bottle of beer on the wall, 1 bottle of beer.
Take it down and pass it around, no more bottles of beer on the wall.

No more bottles of beer on the wall, no more bottles of beer.
Go to the store and buy some more, 99 bottles of beer on the wall.

For bonus points

Did you get the tests passing and the code clean? If you want to, these are some additional things you could try:

Remove as much duplication as you possibly can.
Optimize for readability, even if it means introducing duplication.
If you've removed all the duplication, do you have a lot of conditionals? Try replacing the conditionals with polymorphism, if it applies in this language. How readable is it?

Then please share your thoughts in a comment on the submission. Did this experiment make the code better? Worse? Did you learn anything from it?

Running tests

Execute the tests with:

$ elixir beer_song_test.exs

Pending tests

In the test suites, all but the first test have been skipped.

Once you get a test passing, you can unskip the next one by commenting out the relevant @tag :pending with a # symbol.

For example:

# @tag :pending
test "shouting" do
  assert Bob.hey("WATCH OUT!") == "Whoa, chill out!"
end

Or, you can enable all the tests by commenting out the ExUnit.configure line in the test suite.

# ExUnit.configure exclude: :pending, trace: true

For more detailed information about the Elixir track, please see the help page.

Source

Learn to Program by Chris Pine http://pine.fm/LearnToProgram/?Chapter=06

Submitting Incomplete Solutions

It's possible to submit an incomplete solution so you can see how others have completed the exercise.

beer_song_test.exs

if !System.get_env("EXERCISM_TEST_EXAMPLES") do
  Code.load_file("beer_song.exs", __DIR__)
end

ExUnit.start()
ExUnit.configure(exclude: :pending, trace: true)

defmodule BeerSongTest do
  use ExUnit.Case

  test "getting the first verse (99 bottles)" do
    assert BeerSong.verse(99) == """
           99 bottles of beer on the wall, 99 bottles of beer.
           Take one down and pass it around, 98 bottles of beer on the wall.
           """
  end

  @tag :pending
  test "getting the second verse (98 bottles)" do
    assert BeerSong.verse(98) == """
           98 bottles of beer on the wall, 98 bottles of beer.
           Take one down and pass it around, 97 bottles of beer on the wall.
           """
  end

  @tag :pending
  test "getting just the penultimate verse" do
    assert BeerSong.verse(1) == """
           1 bottle of beer on the wall, 1 bottle of beer.
           Take it down and pass it around, no more bottles of beer on the wall.
           """
  end

  @tag :pending
  test "getting just the last verse" do
    assert BeerSong.verse(0) == """
           No more bottles of beer on the wall, no more bottles of beer.
           Go to the store and buy some more, 99 bottles of beer on the wall.
           """
  end

  @tag :pending
  test "getting the last 4 verses" do
    assert BeerSong.lyrics(3..0) == """
           3 bottles of beer on the wall, 3 bottles of beer.
           Take one down and pass it around, 2 bottles of beer on the wall.

           2 bottles of beer on the wall, 2 bottles of beer.
           Take one down and pass it around, 1 bottle of beer on the wall.

           1 bottle of beer on the wall, 1 bottle of beer.
           Take it down and pass it around, no more bottles of beer on the wall.

           No more bottles of beer on the wall, no more bottles of beer.
           Go to the store and buy some more, 99 bottles of beer on the wall.
           """
  end

  @tag :pending
  test "getting the whole song" do
    assert BeerSong.lyrics() == """
           99 bottles of beer on the wall, 99 bottles of beer.
           Take one down and pass it around, 98 bottles of beer on the wall.

           98 bottles of beer on the wall, 98 bottles of beer.
           Take one down and pass it around, 97 bottles of beer on the wall.

           97 bottles of beer on the wall, 97 bottles of beer.
           Take one down and pass it around, 96 bottles of beer on the wall.

           96 bottles of beer on the wall, 96 bottles of beer.
           Take one down and pass it around, 95 bottles of beer on the wall.

           95 bottles of beer on the wall, 95 bottles of beer.
           Take one down and pass it around, 94 bottles of beer on the wall.

           94 bottles of beer on the wall, 94 bottles of beer.
           Take one down and pass it around, 93 bottles of beer on the wall.

           93 bottles of beer on the wall, 93 bottles of beer.
           Take one down and pass it around, 92 bottles of beer on the wall.

           92 bottles of beer on the wall, 92 bottles of beer.
           Take one down and pass it around, 91 bottles of beer on the wall.

           91 bottles of beer on the wall, 91 bottles of beer.
           Take one down and pass it around, 90 bottles of beer on the wall.

           90 bottles of beer on the wall, 90 bottles of beer.
           Take one down and pass it around, 89 bottles of beer on the wall.

           89 bottles of beer on the wall, 89 bottles of beer.
           Take one down and pass it around, 88 bottles of beer on the wall.

           88 bottles of beer on the wall, 88 bottles of beer.
           Take one down and pass it around, 87 bottles of beer on the wall.

           87 bottles of beer on the wall, 87 bottles of beer.
           Take one down and pass it around, 86 bottles of beer on the wall.

           86 bottles of beer on the wall, 86 bottles of beer.
           Take one down and pass it around, 85 bottles of beer on the wall.

           85 bottles of beer on the wall, 85 bottles of beer.
           Take one down and pass it around, 84 bottles of beer on the wall.

           84 bottles of beer on the wall, 84 bottles of beer.
           Take one down and pass it around, 83 bottles of beer on the wall.

           83 bottles of beer on the wall, 83 bottles of beer.
           Take one down and pass it around, 82 bottles of beer on the wall.

           82 bottles of beer on the wall, 82 bottles of beer.
           Take one down and pass it around, 81 bottles of beer on the wall.

           81 bottles of beer on the wall, 81 bottles of beer.
           Take one down and pass it around, 80 bottles of beer on the wall.

           80 bottles of beer on the wall, 80 bottles of beer.
           Take one down and pass it around, 79 bottles of beer on the wall.

           79 bottles of beer on the wall, 79 bottles of beer.
           Take one down and pass it around, 78 bottles of beer on the wall.

           78 bottles of beer on the wall, 78 bottles of beer.
           Take one down and pass it around, 77 bottles of beer on the wall.

           77 bottles of beer on the wall, 77 bottles of beer.
           Take one down and pass it around, 76 bottles of beer on the wall.

           76 bottles of beer on the wall, 76 bottles of beer.
           Take one down and pass it around, 75 bottles of beer on the wall.

           75 bottles of beer on the wall, 75 bottles of beer.
           Take one down and pass it around, 74 bottles of beer on the wall.

           74 bottles of beer on the wall, 74 bottles of beer.
           Take one down and pass it around, 73 bottles of beer on the wall.

           73 bottles of beer on the wall, 73 bottles of beer.
           Take one down and pass it around, 72 bottles of beer on the wall.

           72 bottles of beer on the wall, 72 bottles of beer.
           Take one down and pass it around, 71 bottles of beer on the wall.

           71 bottles of beer on the wall, 71 bottles of beer.
           Take one down and pass it around, 70 bottles of beer on the wall.

           70 bottles of beer on the wall, 70 bottles of beer.
           Take one down and pass it around, 69 bottles of beer on the wall.

           69 bottles of beer on the wall, 69 bottles of beer.
           Take one down and pass it around, 68 bottles of beer on the wall.

           68 bottles of beer on the wall, 68 bottles of beer.
           Take one down and pass it around, 67 bottles of beer on the wall.

           67 bottles of beer on the wall, 67 bottles of beer.
           Take one down and pass it around, 66 bottles of beer on the wall.

           66 bottles of beer on the wall, 66 bottles of beer.
           Take one down and pass it around, 65 bottles of beer on the wall.

           65 bottles of beer on the wall, 65 bottles of beer.
           Take one down and pass it around, 64 bottles of beer on the wall.

           64 bottles of beer on the wall, 64 bottles of beer.
           Take one down and pass it around, 63 bottles of beer on the wall.

           63 bottles of beer on the wall, 63 bottles of beer.
           Take one down and pass it around, 62 bottles of beer on the wall.

           62 bottles of beer on the wall, 62 bottles of beer.
           Take one down and pass it around, 61 bottles of beer on the wall.

           61 bottles of beer on the wall, 61 bottles of beer.
           Take one down and pass it around, 60 bottles of beer on the wall.

           60 bottles of beer on the wall, 60 bottles of beer.
           Take one down and pass it around, 59 bottles of beer on the wall.

           59 bottles of beer on the wall, 59 bottles of beer.
           Take one down and pass it around, 58 bottles of beer on the wall.

           58 bottles of beer on the wall, 58 bottles of beer.
           Take one down and pass it around, 57 bottles of beer on the wall.

           57 bottles of beer on the wall, 57 bottles of beer.
           Take one down and pass it around, 56 bottles of beer on the wall.

           56 bottles of beer on the wall, 56 bottles of beer.
           Take one down and pass it around, 55 bottles of beer on the wall.

           55 bottles of beer on the wall, 55 bottles of beer.
           Take one down and pass it around, 54 bottles of beer on the wall.

           54 bottles of beer on the wall, 54 bottles of beer.
           Take one down and pass it around, 53 bottles of beer on the wall.

           53 bottles of beer on the wall, 53 bottles of beer.
           Take one down and pass it around, 52 bottles of beer on the wall.

           52 bottles of beer on the wall, 52 bottles of beer.
           Take one down and pass it around, 51 bottles of beer on the wall.

           51 bottles of beer on the wall, 51 bottles of beer.
           Take one down and pass it around, 50 bottles of beer on the wall.

           50 bottles of beer on the wall, 50 bottles of beer.
           Take one down and pass it around, 49 bottles of beer on the wall.

           49 bottles of beer on the wall, 49 bottles of beer.
           Take one down and pass it around, 48 bottles of beer on the wall.

           48 bottles of beer on the wall, 48 bottles of beer.
           Take one down and pass it around, 47 bottles of beer on the wall.

           47 bottles of beer on the wall, 47 bottles of beer.
           Take one down and pass it around, 46 bottles of beer on the wall.

           46 bottles of beer on the wall, 46 bottles of beer.
           Take one down and pass it around, 45 bottles of beer on the wall.

           45 bottles of beer on the wall, 45 bottles of beer.
           Take one down and pass it around, 44 bottles of beer on the wall.

           44 bottles of beer on the wall, 44 bottles of beer.
           Take one down and pass it around, 43 bottles of beer on the wall.

           43 bottles of beer on the wall, 43 bottles of beer.
           Take one down and pass it around, 42 bottles of beer on the wall.

           42 bottles of beer on the wall, 42 bottles of beer.
           Take one down and pass it around, 41 bottles of beer on the wall.

           41 bottles of beer on the wall, 41 bottles of beer.
           Take one down and pass it around, 40 bottles of beer on the wall.

           40 bottles of beer on the wall, 40 bottles of beer.
           Take one down and pass it around, 39 bottles of beer on the wall.

           39 bottles of beer on the wall, 39 bottles of beer.
           Take one down and pass it around, 38 bottles of beer on the wall.

           38 bottles of beer on the wall, 38 bottles of beer.
           Take one down and pass it around, 37 bottles of beer on the wall.

           37 bottles of beer on the wall, 37 bottles of beer.
           Take one down and pass it around, 36 bottles of beer on the wall.

           36 bottles of beer on the wall, 36 bottles of beer.
           Take one down and pass it around, 35 bottles of beer on the wall.

           35 bottles of beer on the wall, 35 bottles of beer.
           Take one down and pass it around, 34 bottles of beer on the wall.

           34 bottles of beer on the wall, 34 bottles of beer.
           Take one down and pass it around, 33 bottles of beer on the wall.

           33 bottles of beer on the wall, 33 bottles of beer.
           Take one down and pass it around, 32 bottles of beer on the wall.

           32 bottles of beer on the wall, 32 bottles of beer.
           Take one down and pass it around, 31 bottles of beer on the wall.

           31 bottles of beer on the wall, 31 bottles of beer.
           Take one down and pass it around, 30 bottles of beer on the wall.

           30 bottles of beer on the wall, 30 bottles of beer.
           Take one down and pass it around, 29 bottles of beer on the wall.

           29 bottles of beer on the wall, 29 bottles of beer.
           Take one down and pass it around, 28 bottles of beer on the wall.

           28 bottles of beer on the wall, 28 bottles of beer.
           Take one down and pass it around, 27 bottles of beer on the wall.

           27 bottles of beer on the wall, 27 bottles of beer.
           Take one down and pass it around, 26 bottles of beer on the wall.

           26 bottles of beer on the wall, 26 bottles of beer.
           Take one down and pass it around, 25 bottles of beer on the wall.

           25 bottles of beer on the wall, 25 bottles of beer.
           Take one down and pass it around, 24 bottles of beer on the wall.

           24 bottles of beer on the wall, 24 bottles of beer.
           Take one down and pass it around, 23 bottles of beer on the wall.

           23 bottles of beer on the wall, 23 bottles of beer.
           Take one down and pass it around, 22 bottles of beer on the wall.

           22 bottles of beer on the wall, 22 bottles of beer.
           Take one down and pass it around, 21 bottles of beer on the wall.

           21 bottles of beer on the wall, 21 bottles of beer.
           Take one down and pass it around, 20 bottles of beer on the wall.

           20 bottles of beer on the wall, 20 bottles of beer.
           Take one down and pass it around, 19 bottles of beer on the wall.

           19 bottles of beer on the wall, 19 bottles of beer.
           Take one down and pass it around, 18 bottles of beer on the wall.

           18 bottles of beer on the wall, 18 bottles of beer.
           Take one down and pass it around, 17 bottles of beer on the wall.

           17 bottles of beer on the wall, 17 bottles of beer.
           Take one down and pass it around, 16 bottles of beer on the wall.

           16 bottles of beer on the wall, 16 bottles of beer.
           Take one down and pass it around, 15 bottles of beer on the wall.

           15 bottles of beer on the wall, 15 bottles of beer.
           Take one down and pass it around, 14 bottles of beer on the wall.

           14 bottles of beer on the wall, 14 bottles of beer.
           Take one down and pass it around, 13 bottles of beer on the wall.

           13 bottles of beer on the wall, 13 bottles of beer.
           Take one down and pass it around, 12 bottles of beer on the wall.

           12 bottles of beer on the wall, 12 bottles of beer.
           Take one down and pass it around, 11 bottles of beer on the wall.

           11 bottles of beer on the wall, 11 bottles of beer.
           Take one down and pass it around, 10 bottles of beer on the wall.

           10 bottles of beer on the wall, 10 bottles of beer.
           Take one down and pass it around, 9 bottles of beer on the wall.

           9 bottles of beer on the wall, 9 bottles of beer.
           Take one down and pass it around, 8 bottles of beer on the wall.

           8 bottles of beer on the wall, 8 bottles of beer.
           Take one down and pass it around, 7 bottles of beer on the wall.

           7 bottles of beer on the wall, 7 bottles of beer.
           Take one down and pass it around, 6 bottles of beer on the wall.

           6 bottles of beer on the wall, 6 bottles of beer.
           Take one down and pass it around, 5 bottles of beer on the wall.

           5 bottles of beer on the wall, 5 bottles of beer.
           Take one down and pass it around, 4 bottles of beer on the wall.

           4 bottles of beer on the wall, 4 bottles of beer.
           Take one down and pass it around, 3 bottles of beer on the wall.

           3 bottles of beer on the wall, 3 bottles of beer.
           Take one down and pass it around, 2 bottles of beer on the wall.

           2 bottles of beer on the wall, 2 bottles of beer.
           Take one down and pass it around, 1 bottle of beer on the wall.

           1 bottle of beer on the wall, 1 bottle of beer.
           Take it down and pass it around, no more bottles of beer on the wall.

           No more bottles of beer on the wall, no more bottles of beer.
           Go to the store and buy some more, 99 bottles of beer on the wall.
           """
  end
end

defmodule BeerSong do
  @where "on the wall"
  @doc """
  Get a single verse of the beer song
  """
  @spec verse(integer) :: String.t
  def verse(number) do
    # Could have put functions in terms of verse number,
    # but by number of bottles is MUCH clearer!
    count = rem(number - 2, 100) + 1
    """
#{how_many_what(count, :capitalized)} #{@where}, #{how_many_what(count)}.
#{action(count)}, #{how_many_what(remainder(count))} #{@where}.
    """
  end

  defp how_many_what(count, treatment \\ :none) do
    "#{how_many(count, treatment)} bottle#{pluralizer(count)} of beer"
  end

  defp how_many(0, :capitalized), do: "No more"
  defp how_many(0, _), do: "no more"
  defp how_many(count, _), do: count

  defp pluralizer(1), do: ""
  defp pluralizer(_), do: "s"

  defp action(0), do: "Go to the store and buy some more"
  defp action(count) do
    "Take #{to_pass(count)} down and pass it around"
  end

  defp to_pass(1), do: "it"
  defp to_pass(_), do: "one"

  # could also do modulo math, but this reveals intent better imho
  defp remainder(0), do: 99
  defp remainder(count), do: count - 1

  @doc """
  Get the entire beer song for a given range of numbers of bottles.
  """
  @spec lyrics(Range.t) :: String.t
  def lyrics(range \\ 100..1) do
    Enum.map(range, &(verse &1)) |> Enum.join("\n")
  end
end

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davearonson's solution

to Beer Song in the Elixir Track