al_fixatan2 man page

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.

Info

Allegro reference manual