fixatan2(3)                     Allegro manual                     fixatan2(3)



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

SYNOPSIS
       #include <allegro.h>


       fixed fixatan2(fixed y, fixed x);

DESCRIPTION
       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);
          ASSERT(!errno);

RETURN VALUE
       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.


SEE ALSO
       , exlights(3), exspline(3)



Allegro                          version 4.2.3                     fixatan2(3)
