fixatan2 (3) Linux Manual Page

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)