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compkl.c revision 1.5 
      1 /*	$NetBSD: compkl.c,v 1.5 2003/08/07 09:37:50 agc Exp $	*/
      2 
      3 /*
      4  * Copyright (c) 1980, 1993
      5  *	The Regents of the University of California.  All rights reserved.
      6  *
      7  * Redistribution and use in source and binary forms, with or without
      8  * modification, are permitted provided that the following conditions
      9  * are met:
     10  * 1. Redistributions of source code must retain the above copyright
     11  *    notice, this list of conditions and the following disclaimer.
     12  * 2. Redistributions in binary form must reproduce the above copyright
     13  *    notice, this list of conditions and the following disclaimer in the
     14  *    documentation and/or other materials provided with the distribution.
     15  * 3. Neither the name of the University nor the names of its contributors
     16  *    may be used to endorse or promote products derived from this software
     17  *    without specific prior written permission.
     18  *
     19  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
     20  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     21  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     22  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
     23  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     24  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     25  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     26  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     27  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     28  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     29  * SUCH DAMAGE.
     30  */
     31 
     32 #include <sys/cdefs.h>
     33 #ifndef lint
     34 #if 0
     35 static char sccsid[] = "@(#)compkl.c	8.1 (Berkeley) 5/31/93";
     36 #else
     37 __RCSID("$NetBSD: compkl.c,v 1.5 2003/08/07 09:37:50 agc Exp $");
     38 #endif
     39 #endif /* not lint */
     40 
     41 #include <math.h>
     42 #include "trek.h"
     43 
     44 /*
     45 **  compute klingon distances
     46 **
     47 **	The klingon list has the distances for all klingons recomputed
     48 **	and sorted.  The parameter is a Boolean flag which is set if
     49 **	we have just entered a new quadrant.
     50 **
     51 **	This routine is used every time the Enterprise or the Klingons
     52 **	move.
     53 */
     54 
     55 static void sortkl __P((void));
     56 
     57 void
     58 compkldist(f)
     59 int	f;		/* set if new quadrant */
     60 {
     61 	int		i, dx, dy;
     62 	double		d;
     63 	double		temp;
     64 
     65 	if (Etc.nkling == 0)
     66 		return;
     67 	for (i = 0; i < Etc.nkling; i++)
     68 	{
     69 		/* compute distance to the Klingon */
     70 		dx = Ship.sectx - Etc.klingon[i].x;
     71 		dy = Ship.secty - Etc.klingon[i].y;
     72 		d = dx * dx + dy * dy;
     73 		d = sqrt(d);
     74 
     75 		/* compute average of new and old distances to Klingon */
     76 		if (!f)
     77 		{
     78 			temp = Etc.klingon[i].dist;
     79 			Etc.klingon[i].avgdist = 0.5 * (temp + d);
     80 		}
     81 		else
     82 		{
     83 			/* new quadrant: average is current */
     84 			Etc.klingon[i].avgdist = d;
     85 		}
     86 		Etc.klingon[i].dist = d;
     87 	}
     88 
     89 	/* leave them sorted */
     90 	sortkl();
     91 }
     92 
     93 
     94 /*
     95 **  sort klingons
     96 **
     97 **	bubble sort on ascending distance
     98 */
     99 
    100 static void
    101 sortkl()
    102 {
    103 	struct kling		t;
    104 	int		f, i, m;
    105 
    106 	m = Etc.nkling - 1;
    107 	f = 1;
    108 	while (f)
    109 	{
    110 		f = 0;
    111 		for (i = 0; i < m; i++)
    112 			if (Etc.klingon[i].dist > Etc.klingon[i+1].dist)
    113 			{
    114 				t =  Etc.klingon[i];
    115 				Etc.klingon[i] = Etc.klingon[i+1];
    116 				Etc.klingon[i+1] = t;
    117 				f = 1;
    118 			}
    119 	}
    120 }
    121