fixatan2(3) Fixed point version of the libc atan2() routine. Allegro game programming library.


#include <allegro.h>

fixed fixatan2(fixed y, fixed x);


This is a fixed point version of the libc atan2() routine. It computes the arc tangent of `y / x', but the signs of both arguments are used to determine the quadrant of the result, and `x' is permitted to be zero. This function is useful to convert Cartesian coordinates to polar coordinates. Example:

   fixed result;
   /* Sets `result' to binary angle 64. */
   result = fixatan2(itofix(1), 0);
   /* Sets `result' to binary angle -109. */
   result = fixatan2(itofix(-1), itofix(-2));
   /* Fails the assert. */
   result = fixatan2(0, 0);


Returns the arc tangent of `y / x' in fixed point binary format angle, from `-128' to `128'. If both `x' and `y' are zero, returns zero and sets `errno' to EDOM.