// written by Don Clugston:
//    https://www.digitalmars.com/d/archives/digitalmars/D/announce/4374.html
//    http://www.99-bottles-of-beer.net/language-d-1212.html

// Generates the "99 bottles of beer" song at compile time,
// using the template metaprograming facilities of D.
// No executable is generated. No libraries are used.
// Illustrates template default values, template string value parameters,
// compile-time concatenation of constant strings, static if.

module bottles99;

template decimaldigit(int n) {
    const string decimaldigit = "0123456789"[n..n+1];
}

template itoa(ulong n)
{
    static if ( n < 10L )
	const string itoa = decimaldigit!(n);
    else
	const string itoa = itoa!( n / 10L ) ~ decimaldigit!( n % 10L );
}

template showHowMany(int n, string where, bool needcapital = false)
{
  static if ( n > 1 )
      const string showHowMany = itoa!(n) ~ " bottles of beer" ~ where ~ "\n";
  else static if ( n == 1 )
      const string showHowMany = "1 bottle of beer" ~ where ~ "\n";
  else static if ( needcapital )
      const string showHowMany = "No more bottles of beer" ~ where ~ "\n";
  else
      const string showHowMany = "no more bottles of beer" ~ where ~ "\n";
}

template beer(int maxbeers, int n = maxbeers)
{
  static if ( n > 0 )
    const string beer = showHowMany!(n, " on the wall,", true)
        ~ showHowMany!(n, ".")
        ~ "Take one down and pass it around," ~ "\n"
        ~ showHowMany!( n - 1 , " on the wall.")
        ~ "\n" ~ beer!(maxbeers, n - 1); // recurse for subsequent verses.
  else
    const string beer = showHowMany!(n, " on the wall,", true)
        ~ showHowMany!(n, ".")
        ~ "Go to the store and buy some more," ~ "\n"
        ~ showHowMany!( maxbeers, " on the wall.");
}

enum expected = `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 one 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.
`;

static assert(beer!(99) == expected);