Template:99BoB

From Stiki

This template prints a set of lyrics for the traditional song, 99 Bottles of Beer.

Usage

{{99BoB}}

Required extensions

The following extensions must be installed in order for this template to work:

ParserFunctions

Includes functionality for conditional statements (this template uses #ifeq and #expr).

Variables

Allows the use of variables to store and retrieve values within the same wiki page (this template uses #vardefine and #var).

Loops

Allows the use of loops within a template, as opposed to allowing a template to call itself (this template uses #while).

Background

Intuitively, one might expect the following piece of code to produce the required effect:

{{#if:{{{1|}}}|{{{1}}} bottle{{#ifeq:{{{1}}}|1||s}} of beer on the wall,
{{{1}}} bottle{{#ifeq:{{{1}}}|1||s}} of beer.
Take one down and pass it around.
{{#ifeq:{{{1}}}|1|No more|{{#expr:{{{1}}}-1}}}} bottle{{#ifeq:{{{1}}}|2||s}} of beer on the wall.{{#ifeq:{{{1}}}|1||

{{99BoB|{{#expr:{{{1}}}-1}}}}}}|{{99BoB|99}}}}

However, MediaWiki software specifically checks for loops in templates and upon discovering one will cease parsing the template, returning the error message, "Template loop detected". This cannot be circumvented (nor should it since to disable this error trapping would open a wiki to the possibility of an infinite loop in the template parser, which may have a similar effect to a Denial of Service attack).

Instead there are some additional extensions (listed above) that allow the use of variables and loops within a template.

It is of interest to note that to prevent infinite loops in templates written using the Loops extension, all loops computed by that extension are limited to 100 iterations. This template just sneaks in at 99/100, so it works for the strict requirements of the challenge but it isn't scalable. Be aware that the use of loops noticeably increases the page load time.

Underlying source code

Here is a copy of the underlying active code for this template:

{{#vardefine:bottles|99}}{{#while:|{{#var:bottles}}
|{{#var:bottles}} bottle{{#ifeq:{{#var:bottles}}|1||s}} of beer on the wall,
<BR>{{#var:bottles}} bottle{{#ifeq:{{#var:bottles}}|1||s}} of beer.
<BR>Take 1 down and pass it around.
<BR>{{#ifeq:{{#var:bottles}}|1|No more|{{#expr:{{#var:bottles}}-1}}}} bottle{{#ifeq:{{#var:bottles}}|2||s}} of beer on the wall.
<BR><BR>{{#vardefine:bottles|{{#ifeq:{{#var:bottles}}|1||{{#expr:{{#var:bottles}}-1}}}}}}
}}

If you wish to verify this source code, click on the "edit" tab at the top of the page (if you are a registered user) or the "view source" tab (if you are not).

Template code

99 bottles of beer on the wall,
99 bottles of beer.
Take 1 down and pass it around.
98 bottles of beer on the wall.

98 bottles of beer on the wall,
98 bottles of beer.
Take 1 down and pass it around.
97 bottles of beer on the wall.

97 bottles of beer on the wall,
97 bottles of beer.
Take 1 down and pass it around.
96 bottles of beer on the wall.

96 bottles of beer on the wall,
96 bottles of beer.
Take 1 down and pass it around.
95 bottles of beer on the wall.

95 bottles of beer on the wall,
95 bottles of beer.
Take 1 down and pass it around.
94 bottles of beer on the wall.

94 bottles of beer on the wall,
94 bottles of beer.
Take 1 down and pass it around.
93 bottles of beer on the wall.

93 bottles of beer on the wall,
93 bottles of beer.
Take 1 down and pass it around.
92 bottles of beer on the wall.

92 bottles of beer on the wall,
92 bottles of beer.
Take 1 down and pass it around.
91 bottles of beer on the wall.

91 bottles of beer on the wall,
91 bottles of beer.
Take 1 down and pass it around.
90 bottles of beer on the wall.

90 bottles of beer on the wall,
90 bottles of beer.
Take 1 down and pass it around.
89 bottles of beer on the wall.

89 bottles of beer on the wall,
89 bottles of beer.
Take 1 down and pass it around.
88 bottles of beer on the wall.

88 bottles of beer on the wall,
88 bottles of beer.
Take 1 down and pass it around.
87 bottles of beer on the wall.

87 bottles of beer on the wall,
87 bottles of beer.
Take 1 down and pass it around.
86 bottles of beer on the wall.

86 bottles of beer on the wall,
86 bottles of beer.
Take 1 down and pass it around.
85 bottles of beer on the wall.

85 bottles of beer on the wall,
85 bottles of beer.
Take 1 down and pass it around.
84 bottles of beer on the wall.

84 bottles of beer on the wall,
84 bottles of beer.
Take 1 down and pass it around.
83 bottles of beer on the wall.

83 bottles of beer on the wall,
83 bottles of beer.
Take 1 down and pass it around.
82 bottles of beer on the wall.

82 bottles of beer on the wall,
82 bottles of beer.
Take 1 down and pass it around.
81 bottles of beer on the wall.

81 bottles of beer on the wall,
81 bottles of beer.
Take 1 down and pass it around.
80 bottles of beer on the wall.

80 bottles of beer on the wall,
80 bottles of beer.
Take 1 down and pass it around.
79 bottles of beer on the wall.

79 bottles of beer on the wall,
79 bottles of beer.
Take 1 down and pass it around.
78 bottles of beer on the wall.

78 bottles of beer on the wall,
78 bottles of beer.
Take 1 down and pass it around.
77 bottles of beer on the wall.

77 bottles of beer on the wall,
77 bottles of beer.
Take 1 down and pass it around.
76 bottles of beer on the wall.

76 bottles of beer on the wall,
76 bottles of beer.
Take 1 down and pass it around.
75 bottles of beer on the wall.

75 bottles of beer on the wall,
75 bottles of beer.
Take 1 down and pass it around.
74 bottles of beer on the wall.

74 bottles of beer on the wall,
74 bottles of beer.
Take 1 down and pass it around.
73 bottles of beer on the wall.

73 bottles of beer on the wall,
73 bottles of beer.
Take 1 down and pass it around.
72 bottles of beer on the wall.

72 bottles of beer on the wall,
72 bottles of beer.
Take 1 down and pass it around.
71 bottles of beer on the wall.

71 bottles of beer on the wall,
71 bottles of beer.
Take 1 down and pass it around.
70 bottles of beer on the wall.

70 bottles of beer on the wall,
70 bottles of beer.
Take 1 down and pass it around.
69 bottles of beer on the wall.

69 bottles of beer on the wall,
69 bottles of beer.
Take 1 down and pass it around.
68 bottles of beer on the wall.

68 bottles of beer on the wall,
68 bottles of beer.
Take 1 down and pass it around.
67 bottles of beer on the wall.

67 bottles of beer on the wall,
67 bottles of beer.
Take 1 down and pass it around.
66 bottles of beer on the wall.

66 bottles of beer on the wall,
66 bottles of beer.
Take 1 down and pass it around.
65 bottles of beer on the wall.

65 bottles of beer on the wall,
65 bottles of beer.
Take 1 down and pass it around.
64 bottles of beer on the wall.

64 bottles of beer on the wall,
64 bottles of beer.
Take 1 down and pass it around.
63 bottles of beer on the wall.

63 bottles of beer on the wall,
63 bottles of beer.
Take 1 down and pass it around.
62 bottles of beer on the wall.

62 bottles of beer on the wall,
62 bottles of beer.
Take 1 down and pass it around.
61 bottles of beer on the wall.

61 bottles of beer on the wall,
61 bottles of beer.
Take 1 down and pass it around.
60 bottles of beer on the wall.

60 bottles of beer on the wall,
60 bottles of beer.
Take 1 down and pass it around.
59 bottles of beer on the wall.

59 bottles of beer on the wall,
59 bottles of beer.
Take 1 down and pass it around.
58 bottles of beer on the wall.

58 bottles of beer on the wall,
58 bottles of beer.
Take 1 down and pass it around.
57 bottles of beer on the wall.

57 bottles of beer on the wall,
57 bottles of beer.
Take 1 down and pass it around.
56 bottles of beer on the wall.

56 bottles of beer on the wall,
56 bottles of beer.
Take 1 down and pass it around.
55 bottles of beer on the wall.

55 bottles of beer on the wall,
55 bottles of beer.
Take 1 down and pass it around.
54 bottles of beer on the wall.

54 bottles of beer on the wall,
54 bottles of beer.
Take 1 down and pass it around.
53 bottles of beer on the wall.

53 bottles of beer on the wall,
53 bottles of beer.
Take 1 down and pass it around.
52 bottles of beer on the wall.

52 bottles of beer on the wall,
52 bottles of beer.
Take 1 down and pass it around.
51 bottles of beer on the wall.

51 bottles of beer on the wall,
51 bottles of beer.
Take 1 down and pass it around.
50 bottles of beer on the wall.

50 bottles of beer on the wall,
50 bottles of beer.
Take 1 down and pass it around.
49 bottles of beer on the wall.

49 bottles of beer on the wall,
49 bottles of beer.
Take 1 down and pass it around.
48 bottles of beer on the wall.

48 bottles of beer on the wall,
48 bottles of beer.
Take 1 down and pass it around.
47 bottles of beer on the wall.

47 bottles of beer on the wall,
47 bottles of beer.
Take 1 down and pass it around.
46 bottles of beer on the wall.

46 bottles of beer on the wall,
46 bottles of beer.
Take 1 down and pass it around.
45 bottles of beer on the wall.

45 bottles of beer on the wall,
45 bottles of beer.
Take 1 down and pass it around.
44 bottles of beer on the wall.

44 bottles of beer on the wall,
44 bottles of beer.
Take 1 down and pass it around.
43 bottles of beer on the wall.

43 bottles of beer on the wall,
43 bottles of beer.
Take 1 down and pass it around.
42 bottles of beer on the wall.

42 bottles of beer on the wall,
42 bottles of beer.
Take 1 down and pass it around.
41 bottles of beer on the wall.

41 bottles of beer on the wall,
41 bottles of beer.
Take 1 down and pass it around.
40 bottles of beer on the wall.

40 bottles of beer on the wall,
40 bottles of beer.
Take 1 down and pass it around.
39 bottles of beer on the wall.

39 bottles of beer on the wall,
39 bottles of beer.
Take 1 down and pass it around.
38 bottles of beer on the wall.

38 bottles of beer on the wall,
38 bottles of beer.
Take 1 down and pass it around.
37 bottles of beer on the wall.

37 bottles of beer on the wall,
37 bottles of beer.
Take 1 down and pass it around.
36 bottles of beer on the wall.

36 bottles of beer on the wall,
36 bottles of beer.
Take 1 down and pass it around.
35 bottles of beer on the wall.

35 bottles of beer on the wall,
35 bottles of beer.
Take 1 down and pass it around.
34 bottles of beer on the wall.

34 bottles of beer on the wall,
34 bottles of beer.
Take 1 down and pass it around.
33 bottles of beer on the wall.

33 bottles of beer on the wall,
33 bottles of beer.
Take 1 down and pass it around.
32 bottles of beer on the wall.

32 bottles of beer on the wall,
32 bottles of beer.
Take 1 down and pass it around.
31 bottles of beer on the wall.

31 bottles of beer on the wall,
31 bottles of beer.
Take 1 down and pass it around.
30 bottles of beer on the wall.

30 bottles of beer on the wall,
30 bottles of beer.
Take 1 down and pass it around.
29 bottles of beer on the wall.

29 bottles of beer on the wall,
29 bottles of beer.
Take 1 down and pass it around.
28 bottles of beer on the wall.

28 bottles of beer on the wall,
28 bottles of beer.
Take 1 down and pass it around.
27 bottles of beer on the wall.

27 bottles of beer on the wall,
27 bottles of beer.
Take 1 down and pass it around.
26 bottles of beer on the wall.

26 bottles of beer on the wall,
26 bottles of beer.
Take 1 down and pass it around.
25 bottles of beer on the wall.

25 bottles of beer on the wall,
25 bottles of beer.
Take 1 down and pass it around.
24 bottles of beer on the wall.

24 bottles of beer on the wall,
24 bottles of beer.
Take 1 down and pass it around.
23 bottles of beer on the wall.

23 bottles of beer on the wall,
23 bottles of beer.
Take 1 down and pass it around.
22 bottles of beer on the wall.

22 bottles of beer on the wall,
22 bottles of beer.
Take 1 down and pass it around.
21 bottles of beer on the wall.

21 bottles of beer on the wall,
21 bottles of beer.
Take 1 down and pass it around.
20 bottles of beer on the wall.

20 bottles of beer on the wall,
20 bottles of beer.
Take 1 down and pass it around.
19 bottles of beer on the wall.

19 bottles of beer on the wall,
19 bottles of beer.
Take 1 down and pass it around.
18 bottles of beer on the wall.

18 bottles of beer on the wall,
18 bottles of beer.
Take 1 down and pass it around.
17 bottles of beer on the wall.

17 bottles of beer on the wall,
17 bottles of beer.
Take 1 down and pass it around.
16 bottles of beer on the wall.

16 bottles of beer on the wall,
16 bottles of beer.
Take 1 down and pass it around.
15 bottles of beer on the wall.

15 bottles of beer on the wall,
15 bottles of beer.
Take 1 down and pass it around.
14 bottles of beer on the wall.

14 bottles of beer on the wall,
14 bottles of beer.
Take 1 down and pass it around.
13 bottles of beer on the wall.

13 bottles of beer on the wall,
13 bottles of beer.
Take 1 down and pass it around.
12 bottles of beer on the wall.

12 bottles of beer on the wall,
12 bottles of beer.
Take 1 down and pass it around.
11 bottles of beer on the wall.

11 bottles of beer on the wall,
11 bottles of beer.
Take 1 down and pass it around.
10 bottles of beer on the wall.

10 bottles of beer on the wall,
10 bottles of beer.
Take 1 down and pass it around.
9 bottles of beer on the wall.

9 bottles of beer on the wall,
9 bottles of beer.
Take 1 down and pass it around.
8 bottles of beer on the wall.

8 bottles of beer on the wall,
8 bottles of beer.
Take 1 down and pass it around.
7 bottles of beer on the wall.

7 bottles of beer on the wall,
7 bottles of beer.
Take 1 down and pass it around.
6 bottles of beer on the wall.

6 bottles of beer on the wall,
6 bottles of beer.
Take 1 down and pass it around.
5 bottles of beer on the wall.

5 bottles of beer on the wall,
5 bottles of beer.
Take 1 down and pass it around.
4 bottles of beer on the wall.

4 bottles of beer on the wall,
4 bottles of beer.
Take 1 down and pass it around.
3 bottles of beer on the wall.

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

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

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