[GiNaC-list] How to convert epsilon_tensor in a matrix?

Hi, I have a very naive question: my program compute some dirac_traces, and some epsilon_tensors arises in this process. I have to convert the tensorial structure to matricial to compute it numerically, but until now I don't figure out how to manipulate expressions like this ============= [[31],[0.0],[0.0],[-31]]~sigma*[[6.3],[0.0],[0.0],[6.30]]~alpha*[[19.33],[-1.108],[-5.4],[18.6]].gamma*eps.delta.sigma~gamma.alpha*[[16.781197650788506337],[4.96],[11.38],[11.2]]~gamma ============= Note that the episilon tensor is fully contracted by four (4x1) vectors. I will be glad for any suggestion given! Regards, Marco