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author HackBot
date Sun, 09 Dec 2012 19:30:08 +0000
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1 "Intersections & Splats" is an INTERCAL implementation of one of my
2 favorite games, "Cows & Bulls," now more commonly known by the
3 commercial version, "Mastermind."
4
5 Rules of the Game
6
7 The idea of the game is that one person selects a "code" in the form
8 of a short string of digits, typically four. ("Mastermind" used colors
9 in place of numbers.) The other person has a limited number of chances
10 to guess what the code is. Every move consists of submitting a guess,
11 and the first player replying with a score. Each scoring reveals a
12 little more information about the code. A guess is scored by giving a
13 certain number of cows and a certain number of bulls. These correspond
14 to Mastermind's white pegs and black pegs, respectively - and, in this
15 program, intersections (+) and splats (*).
16
17 This game is perfect for a computer because the person who makes the
18 code has nothing to do but score the other player's guesses - a
19 mechanical task.
20
21 Here's how the scoring works. For every number in the code that is
22 matched by the same number in the same position in the guess, a splat
23 is scored. And for every number in the code that is matched by the
24 same number in the guess, but in the wrong position, an intersection,
25 is scored.
26
27 For example: with a code of "3451" and a guess of "2465", one splat
28 and one intersection would be earned. The splat is for the 4, and the
29 intersection is for the 5. Of course, the player making the guesses
30 isn't told which numbers earned what - that's what they have to
31 deduce. A guess of "6152" gets exactly the same score, even though the
32 intersection and splat correspond to completely different digits.
33
34 The game continues until the code is discovered or the player runs out
35 of guesses.
36
37 Note that there can be some confusion about how the scoring works with
38 repeated digits. In absence of a better standards body, I have stuck
39 with the version described in the Mastermind rules, which is that a
40 digit in the guess can match up with more than one digit in the code.
41 Another example is in order. Say the code is "2412". A guess of "2544"
42 would earn one splat and two intersections. The splat is for having a
43 2 in the guess in the right position, and one of the intersections is
44 also for having a 2 in the guess, but now in the wrong position. The
45 final intersection is earned by having a 4 in the guess, again in the
46 wrong position. The second 4 in the guess, however, does not affect
47 the scoring.
48
49 Here is an algorithmic description of how scoring is done. The player
50 looks at each digit in the code in turn. If the digit under
51 consideration is matched by the same digit in the same place, a splat
52 is earned. Otherwise, if any other digit in the guess is the same, an
53 intersection is earned.
54
55 For those conversant in C, here is an even more algorithmic
56 description:
57
58 for (i = 0 ; i < digits ; ++i)
59 if (guess[i] == code[i])
60 ++splats;
61 else
62 for (j = 0 ; j < digits ; ++j)
63 if (guess[j] == code[i]) {
64 ++intersections;
65 break;
66 }
67
68 For those conversant in INTERCAL, consult the source code.
69
70 Anyway, enough of this. Play the game a few times; you'll get the idea.
71
72 How To Play
73
74 At each move the board is displayed, which shows you all of your
75 previous guesses. Above each guess are the intersections and splats
76 that they earned. Here is an example of a game in progress:
77
78 +
79 * + + * *
80 (1) (5) (2) ( ) ( ) ( ) ( ) ( ) ( ) ( ) (?)
81 (2) (4) (4) ( ) ( ) ( ) ( ) ( ) ( ) ( ) (?)
82 (4) (4) (3) ( ) ( ) ( ) ( ) ( ) ( ) ( ) (?)
83 (2) (6) (5) ( ) ( ) ( ) ( ) ( ) ( ) ( ) (?)
84
85 The first guess "1242" earned one splat and one intersection. The
86 third guess "2435" earned two splats and one intersection. The player
87 has seven more guesses left. Guesses are typed in at the "MOVE:"
88 prompt.
89
90 At the end of the game, the questions marks at the right are replaced
91 with the code. You are then prompted with "[CNQ]". Enter N to start a
92 new game, Q to quit playing, or C to configure the game (see below). N
93 is the default, so if you just hit enter, or type anything except C or
94 Q, it has the same effect. You can also use any of these commands at
95 the "MOVE:" prompt, if you wish to abandon the current game. In
96 addition, R can be entered during a game to redraw the board.
97
98 Configuring the Game
99
100 The game is set up originally to have ten guesses in a game, four
101 digits in the code, and to use the digits 1 through 6. (This matches
102 the setup of the "Mastermind" game.) The C command can be used to
103 modify these settings, so as to change the difficulty of the game.
104
105 When you enter the C command, you are first prompted for the X
106 setting, the number of guesses allowed; then the Y setting, which is
107 the number of digits in the code; and finally the N setting, the
108 number of digits used in the game. Each number is entered using
109 standard INTERCAL numeric entry. (Yes, I could have used my own numio
110 routines here, but the program is big enough as it is. Besides, I
111 didn't want you to completely forget that you were using an INTERCAL
112 program.) You can enter ZERO at any three prompts to abort the
113 configuration and return to the current game. If any values are higher
114 than ONE FIVE, the value modulo 16 will be used instead. Note that
115 while you can enter a value higher than NINE for the number of digits,
116 you may need to have an ASCII chart handy. (By the way, if anyone
117 wants an EBCDIC version, drop me a line.)
118
119 Other Versions
120
121 I enjoyed writing this program so much, that I created two others
122 based on it. First, there is a colorized version, which requires a
123 VT100/ANSI color terminal, or something compatible. And second, there
124 is a CGI script version that plays this game. A package containing all
125 three versions is available at ftp.muppetlabs.com under
126 /pub/intercal/ins.tar.gz. In addition, you can play the CGI script at
127 http://www.muppetlabs.com/~breadbox/intercal/ins/insstart.html.
128
129 Coda
130
131 That's it. Have fun. Questions, comments, and concerns for my mental
132 health can be directed to breadbox@muppetlabs.com.