Re: [GiNaC-list] non-commutative symbols (again)

Hi, Jan!

1. Why does replacing a non-commutative object with another non-commutative object result in the ncmul becoming a mul? 2. Why is the product of two (different) non-commutative objects a mul and not a ncmul?

In a nutshell, non-commutative objects of the different (C++) types are assumed to commute with each other (say, Dirac matrices commute with Gell-Mann ones). One can change this behavior by overriding the return_type_tinfo() method. See the tutorial (section titled `Non-commutative objects') for more details and examples. Hope this helps, Alexei