al_fixatan23alleg5

Usage

Overview

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.