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compkl.c revision 1.1 
      1 /*
      2  * Copyright (c) 1980 Regents of the University of California.
      3  * 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 
     34 #ifndef lint
     35 static char sccsid[] = "@(#)compkl.c	5.4 (Berkeley) 6/1/90";
     36 #endif /* not lint */
     37 
     38 # include	"trek.h"
     39 
     40 /*
     41 **  compute klingon distances
     42 **
     43 **	The klingon list has the distances for all klingons recomputed
     44 **	and sorted.  The parameter is a Boolean flag which is set if
     45 **	we have just entered a new quadrant.
     46 **
     47 **	This routine is used every time the Enterprise or the Klingons
     48 **	move.
     49 */
     50 
     51 compkldist(f)
     52 int	f;		/* set if new quadrant */
     53 {
     54 	register int		i, dx, dy;
     55 	double			d;
     56 	double			temp;
     57 
     58 	if (Etc.nkling == 0)
     59 		return;
     60 	for (i = 0; i < Etc.nkling; i++)
     61 	{
     62 		/* compute distance to the Klingon */
     63 		dx = Ship.sectx - Etc.klingon[i].x;
     64 		dy = Ship.secty - Etc.klingon[i].y;
     65 		d = dx * dx + dy * dy;
     66 		d = sqrt(d);
     67 
     68 		/* compute average of new and old distances to Klingon */
     69 		if (!f)
     70 		{
     71 			temp = Etc.klingon[i].dist;
     72 			Etc.klingon[i].avgdist = 0.5 * (temp + d);
     73 		}
     74 		else
     75 		{
     76 			/* new quadrant: average is current */
     77 			Etc.klingon[i].avgdist = d;
     78 		}
     79 		Etc.klingon[i].dist = d;
     80 	}
     81 
     82 	/* leave them sorted */
     83 	sortkl();
     84 }
     85 
     86 
     87 /*
     88 **  sort klingons
     89 **
     90 **	bubble sort on ascending distance
     91 */
     92 
     93 sortkl()
     94 {
     95 	struct kling		t;
     96 	register int		f, i, m;
     97 
     98 	m = Etc.nkling - 1;
     99 	f = 1;
    100 	while (f)
    101 	{
    102 		f = 0;
    103 		for (i = 0; i < m; i++)
    104 			if (Etc.klingon[i].dist > Etc.klingon[i+1].dist)
    105 			{
    106 				bmove(&Etc.klingon[i], &t, sizeof t);
    107 				bmove(&Etc.klingon[i+1], &Etc.klingon[i], sizeof t);
    108 				bmove(&t, &Etc.klingon[i+1], sizeof t);
    109 				f = 1;
    110 			}
    111 	}
    112 }
    113