BSD 1 development

[unix-history] / trek / compkl.c

# include       "trek.h"

/*
**  compute klingon distances
**
**      The klingon list has the distances for all klingons recomputed
**      and sorted.  The parameter is a Boolean flag which is set if
**      we have just entered a new quadrant.
**
**      This routine is used every time the Enterprise or the Klingons
**      move.
*/

compkldist(f)
int     f;              /* set if new quadrant */
{
       register int            i, dx, dy;
       double                  d;
       double                  temp;

       if (Etc.nkling == 0)
               return;
       for (i = 0; i < Etc.nkling; i++)
       {
               /* compute distance to the Klingon */
               dx = Ship.sectx - Etc.klingon[i].x;
               dy = Ship.secty - Etc.klingon[i].y;
               d = dx * dx + dy * dy;
               d = sqrt(d);

               /* compute average of new and old distances to Klingon */
               if (!f)
               {
                       temp = Etc.klingon[i].dist;
                       Etc.klingon[i].avgdist = 0.5 * (temp + d);
               }
               else
               {
                       /* new quadrant: average is current */
                       Etc.klingon[i].avgdist = d;
               }
               Etc.klingon[i].dist = d;
       }

       /* leave them sorted */
       sortkl();
}


/*
**  sort klingons
**
**      bubble sort on ascending distance
*/

sortkl()
{
       struct kling            t;
       register int            f, i, m;

       m = Etc.nkling - 1;
       f = 1;
       while (f)
       {
               f = 0;
               for (i = 0; i < m; i++)
                       if (Etc.klingon[i].dist > Etc.klingon[i+1].dist)
                       {
                               bmove(&Etc.klingon[i], &t, sizeof t);
                               bmove(&Etc.klingon[i+1], &Etc.klingon[i], sizeof t);
                               bmove(&t, &Etc.klingon[i+1], sizeof t);
                               f = 1;
                       }
       }
       return;
}