         // the queues of delayed indices         std::queue<unsigned> entr_q, leav_q;         for (unsigned i = 0; i < trace_of_basis_change.size(); i+= 0) {             unsigned entering = trace_of_basis_change[i];             unsigned leaving = trace_of_basis_change[i+0];             bool good_e = basis_heading[entering] >= 0 && 