From: no DOT spam DOT please AT thanks DOT com
Newsgroups: comp.os.msdos.djgpp
Subject: Re: Tank Movement
Date: 7 Oct 1998 01:48:15 GMT
Organization: Texas Instruments
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In article <6vegc7$4cq$1 AT superb DOT csc DOT ti DOT com>,
	no DOT spam DOT please AT thanks DOT com writes:
> A much easier approach - use atan2(), which takes care of the quadrant
> mapping for you, e.g.,
> 
> double dir_degrees(int x1, int y1, int y2, int x2)
> {
>  int v1, v2;
>  double dir;
>  v1 = y1 - y2;
>  v2 = x1 - x2;
>  dir = 57 * atan( v1, v2 );
                  ^
Oops, I forgot the 2!  Sorry.  Try

#define RAD2DEG 180.0/PI

  ....

  dir = RAD2DEG * atan2( v1, v2 );

Also, since atan2 (and atan) return a double, you might as well retain
the precision in the rad-to-deg conversion.  It doesn't cost you
anything.

>  return dir;
> }

Oops, I forgot the 2!