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al_fixatan2(3)                                                  al_fixatan2(3)

NAME
       al_fixatan2 - Allegro 5 API

SYNOPSIS

              #include <allegro5/allegro.h>

              al_fixed al_fixatan2(al_fixed y, al_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:

                  al_fixed result;

                  /* Sets `result' to binary angle 64. */
                  result = al_fixatan2(al_itofix(1), 0);

                  /* Sets `result' to binary angle -109. */
                  result = al_fixatan2(al_itofix(-1), al_itofix(-2));

                  /* Fails the assert. */
                  result = al_fixatan2(0, 0);
                  assert(!al_get_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
       Allegro's errno to EDOM.

Allegro reference manual                                        al_fixatan2(3)