mul method

Q mul(Q o)

Returns the Hamilton product of this quaternion and o.

Not commutative: a.mul(b) != b.mul(a).

Implementation

Q mul(Q o) => _q(
  x*o.w + w*o.x + y*o.z - z*o.y,
  y*o.w + w*o.y + z*o.x - x*o.z,
  z*o.w + w*o.z + x*o.y - y*o.x,
  w*o.w - x*o.x - y*o.y - z*o.z,
);