def Cross_C3V(vec1, vec2, result):
    """Computes the cross product between the 3d vectors vec1 and vec2
    (indexable objects of length 3) and stores the result in the third
    argument, named result."""
    x1, y1, z1 = vec1;
    x2, y2, z2 = vec2;

    result[0] = y1 * z2 - z1 * y2;
    result[1] = z1 * x2 - x1 * z2;
    result[2] = x1 * y2 - y1 * x2;

    return None