quat_mul - Man Page
Multiplies two quaternions. Allegro game programming library.
Synopsis
#include <allegro.h>
void quat_mul(const QUAT *p, const QUAT *q, QUAT *out);
Description
Multiplies two quaternions, storing the result in out. The resulting quaternion will have the same effect as the combination of p and q, ie. when applied to a point, (point * out) = ((point * p) * q). Any number of rotations can be concatenated in this way. Note that quaternion multiplication is not commutative, ie. quat_mul(p, q) != quat_mul(q, p).
Info
version 4.4.3 Allegro manual