debian man page for apply_quat

apply_quat(3alleg4)						  Allegro manual					       apply_quat(3alleg4)

NAME
       apply_quat - Multiplies a point by a quaternion. Allegro game programming library.

SYNOPSIS
       #include <allegro.h>

       void apply_quat(const QUAT *q, float x, y, z, *xout, *yout, *zout);

DESCRIPTION
       Multiplies  the	point  (x,  y,	z)  by	the  quaternion  q,  storing  the result in (*xout, *yout, *zout). This is quite a bit slower than
       apply_matrix_f(), so only use it to translate a few points. If you have many points, it is much more efficient to call quat_to_matrix() and
       then use apply_matrix_f().

Allegro 							   version 4.4.2					       apply_quat(3alleg4)