usr/src/games/backgammon/backgammon/extra.c

/*
 * 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. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *      This product includes software developed by the University of
 *      California, Berkeley and its contributors.
 * 4. 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.
 */

#ifndef lint
static char sccsid[] = "@(#)extra.c     8.1 (Berkeley) 5/31/93";
#endif /* not lint */

#include "back.h"

#ifdef DEBUG
#include <stdio.h>
FILE    *trace;
#endif

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

dble ()  {
        register 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;
        }
}
\f
/*
 * 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.
 */

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

#ifdef DEBUG
        register 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);
}
\f
freemen (b)
int     b;

{
        register 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);
}
\f
trapped (n,inc)
int     n, inc;

{
        register 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);
}
\f
eval ()  {

        register 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);
}