why is GiNaC::symbol commutative??

[smilauer at volny.cz]

Hello,

subject explains it all. I would like to use symbols to represent
matrices. Obvious solution (replacing symbols via
some_ex.sub(some_symbol==some_matrix) does not work for
multiplication of matrices. Other ways to do it?

Thanks. Vaclav.

(If I understand it right, upon replacement of one matrix, one
has matrix*symbol; symbol is supposed to be a scalar, so we have
commutative multiplication; then the other symbol is also
substituted for a matrix, so one gets exception "non-commutative
scalar".)