bsdgames/backgammon/backgammon/extra.c

/*	$NetBSD: extra.c,v 1.5 2003/08/07 09:36:55 agc Exp $	*/

/*
 * Copyright (c) 1980, 1993
 *	The Regents of the University of California.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#include <sys/cdefs.h>
#ifndef lint
#if 0
static char sccsid[] = "@(#)extra.c	8.1 (Berkeley) 5/31/93";
#else
__RCSID("$NetBSD: extra.c,v 1.5 2003/08/07 09:36:55 agc Exp $");
#endif
#endif /* not lint */

#include "back.h"
#include "backlocal.h"

#ifdef DEBUG
FILE   *trace;
#endif

/*
 * dble()
 *	Have the current player double and ask opponent to accept.
 */

void
dble()
{
	int     resp;		/* response to y/n */

	for (;;) {
		writel(" doubles.");	/* indicate double */

		if (cturn == -pnum) {	/* see if computer accepts */
			if (dblgood()) {	/* guess not */
				writel("  Declined.\n");
				nexturn();
				cturn *= -2;	/* indicate loss */
				return;
			} else {/* computer accepts */
				writel("  Accepted.\n");
				gvalue *= 2;	/* double game value */
				dlast = cturn;
				if (tflag)
					gwrite();
				return;
			}
		}
		/* ask if player accepts */
		writel("  Does ");
		writel(cturn == 1 ? color[2] : color[3]);
		writel(" accept?");

		/* get response from yorn, a "2" means he said "p" for print
		 * board. */
		if ((resp = yorn('R')) == 2) {
			writel("  Reprint.\n");
			buflush();
			wrboard();
			writel(*Colorptr);
			continue;
		}
		/* check response */
		if (resp) {
			/* accepted */
			gvalue *= 2;
			dlast = cturn;
			if (tflag)
				gwrite();
			return;
		}
		nexturn();	/* declined */
		cturn *= -2;
		return;
	}
}
/*
 * dblgood ()
 *	Returns 1 if the computer would double in this position.  This
 * is not an exact science.  The computer will decline a double that he
 * would have made.  Accumulated judgments are kept in the variable n,
 * which is in "pips", i.e., the position of each man summed over all
 * men, with opponent's totals negative.  Thus, n should have a positive
 * value of 7 for each move ahead, or a negative value of 7 for each one
 * behind.
 */

int
dblgood()
{
	int     n;		/* accumulated judgment */
	int     OFFC = *offptr;	/* no. of computer's men off */
	int     OFFO = *offopp;	/* no. of player's men off */

#ifdef DEBUG
	int     i;
	if (trace == NULL)
		trace = fopen("bgtrace", "w");
#endif

	/* get real pip value */
	n = eval() * cturn;
#ifdef DEBUG
	fputs("\nDoubles:\nBoard: ", trace);
	for (i = 0; i < 26; i++)
		fprintf(trace, " %d", board[i]);
	fprintf(trace, "\n\tpip = %d, ", n);
#endif

	/* below adjusts pip value according to position judgments */

	/* check men moving off board */
	if (OFFC > -15 || OFFO > -15) {
		if (OFFC < 0 && OFFO < 0) {
			OFFC += 15;
			OFFO += 15;
			n += ((OFFC - OFFO) * 7) / 2;
		} else
			if (OFFC < 0) {
				OFFC += 15;
				n -= OFFO * 7 / 2;
			} else
				if (OFFO < 0) {
					OFFO += 15;
					n += OFFC * 7 / 2;
				}
		if (OFFC < 8 && OFFO > 8)
			n -= 7;
		if (OFFC < 10 && OFFO > 10)
			n -= 7;
		if (OFFC < 12 && OFFO > 12)
			n -= 7;
		if (OFFO < 8 && OFFC > 8)
			n += 7;
		if (OFFO < 10 && OFFC > 10)
			n += 7;
		if (OFFO < 12 && OFFC > 12)
			n += 7;
		n += ((OFFC - OFFO) * 7) / 2;
	}
#ifdef DEBUG
	fprintf(trace, "off = %d, ", n);
#endif

	/* see if men are trapped */
	n -= freemen(bar);
	n += freemen(home);
	n += trapped(home, -cturn);
	n -= trapped(bar, cturn);

#ifdef DEBUG
	fprintf(trace, "free = %d\n", n);
	fprintf(trace, "\tOFFC = %d, OFFO = %d\n", OFFC, OFFO);
	fflush(trace);
#endif

	/* double if 2-3 moves ahead */
	if (n > 10 + rnum(7))
		return (1);
	return (0);
}

int
freemen(b)
	int     b;
{
	int     i, inc, lim;

	odds(0, 0, 0);
	if (board[b] == 0)
		return (0);
	inc = (b == 0 ? 1 : -1);
	lim = (b == 0 ? 7 : 18);
	for (i = b + inc; i != lim; i += inc)
		if (board[i] * inc < -1)
			odds(abs(b - i), 0, abs(board[b]));
	if (abs(board[b]) == 1)
		return ((36 - count()) / 5);
	return (count() / 5);
}

int
trapped(n, inc)
	int     n, inc;
{
	int     i, j, k;
	int     c, l, ct;

	ct = 0;
	l = n + 7 * inc;
	for (i = n + inc; i != l; i += inc) {
		odds(0, 0, 0);
		c = abs(i - l);
		if (board[i] * inc > 0) {
			for (j = c; j < 13; j++)
				if (board[i + inc * j] * inc < -1) {
					if (j < 7)
						odds(j, 0, 1);
					for (k = 1; k < 7 && k < j; k++)
						if (j - k < 7)
							odds(k, j - k, 1);
				}
			ct += abs(board[i]) * (36 - count());
		}
	}
	return (ct / 5);
}

int
eval()
{
	int     i, j;

	for (j = i = 0; i < 26; i++)
		j += (board[i] >= 0 ? i * board[i] : (25 - i) * board[i]);

	if (off[1] >= 0)
		j += 25 * off[1];
	else
		j += 25 * (off[1] + 15);

	if (off[0] >= 0)
		j -= 25 * off[0];
	else
		j -= 25 * (off[0] + 15);
	return (j);
}