For matrix and quaternions multiplication does not output the same type as the input.

For example:

    int a = 1;
    
    a + a = 2; (int)
    a * 2 = 2; (int)


    auto ma = matrix<2, 4>();
    auto mb = matrix<4, 1>();
 
    ma * a  is matrix<2, 4>
    ma * ma is not possible
    ma * mb is matrix<2, 1>

Compilers used to be very bad at telling you what was going on here if you, for example, changed `<2, 4>` to `<3, 4>` or something. g++ now handles it pretty well: https://hastebin.com/idemopikag