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.