1 /*
2  * Copyright (c) 1980, 1993
3  *	The Regents of the University of California.  All rights reserved.
4  *
5  * Redistribution and use in source and binary forms, with or without
6  * modification, are permitted provided that the following conditions
7  * are met:
8  * 1. Redistributions of source code must retain the above copyright
9  *    notice, this list of conditions and the following disclaimer.
10  * 2. Redistributions in binary form must reproduce the above copyright
11  *    notice, this list of conditions and the following disclaimer in the
12  *    documentation and/or other materials provided with the distribution.
13  * 3. All advertising materials mentioning features or use of this software
14  *    must display the following acknowledgement:
15  *	This product includes software developed by the University of
16  *	California, Berkeley and its contributors.
17  * 4. Neither the name of the University nor the names of its contributors
18  *    may be used to endorse or promote products derived from this software
19  *    without specific prior written permission.
20  *
21  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
22  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
23  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
24  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
25  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
26  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
27  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
28  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
29  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
30  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
31  * SUCH DAMAGE.
32  *
33  * @(#)odds.c	8.1 (Berkeley) 5/31/93
34  * $FreeBSD: src/games/backgammon/common_source/odds.c,v 1.5 1999/11/30 03:48:26 billf Exp $
35  * $DragonFly: src/games/backgammon/common_source/odds.c,v 1.3 2006/08/08 16:36:11 pavalos Exp $
36  */
37 
38 #include "back.h"
39 
40 void
41 odds(int r1, int r2, int val)
42 {
43 	int	i, j;
44 
45 	if (r1 == 0)  {
46 		for (i = 0; i < 6; i++)
47 			for (j = 0; j < 6; j++)
48 				table[i][j] = 0;
49 		return;
50 	} else  {
51 		r1--;
52 		if (r2-- == 0)
53 			for (i = 0; i < 6; i++)  {
54 				table[i][r1] += val;
55 				table[r1][i] += val;
56 			}
57 		else  {
58 			table[r2][r1] += val;
59 			table[r1][r2] += val;
60 		}
61 	}
62 }
63 
64 int
65 count(void)
66 {
67 	int	i;
68 	int	j;
69 	int	total;
70 
71 	total = 0;
72 	for (i = 0; i < 6; i++)
73 		for (j = 0; j < 6; j++)
74 			total += table[i][j];
75 	return (total);
76 }
77 
78 int
79 canhit(int i, int c)
80 {
81 	int	j, k, b;
82 	int	a, diff, place, addon, menstuck;
83 
84 	if (c == 0)
85 		odds (0,0,0);
86 	if (board[i] > 0)  {
87 		a = -1;
88 		b = 25;
89 	} else  {
90 		a = 1;
91 		b = 0;
92 	}
93 	place = abs (25-b-i);
94 	menstuck = abs (board[b]);
95 	for (j = b; j != i; j += a)  {
96 		if (board[j]*a > 0)  {
97 			diff = abs(j-i);
98 			addon = place+((board[j]*a > 2 || j == b)? 5: 0);
99 			if ((j == b && menstuck == 1) &&
100 			    (j != b && menstuck == 0))
101 				for (k = 1; k < diff; k++)
102 					if (k < 7 && diff-k < 7 &&
103 					    (board[i+a*k]*a >= 0 ||
104 					    board[i+a*(diff-k)] >= 0))
105 						odds (k,diff-k,addon);
106 			if ((j == b || menstuck < 2) && diff < 7)
107 				odds (diff,0,addon);
108 		}
109 		if (j == b && menstuck > 1)
110 			break;
111 	}
112 	return (count());
113 }
114