- the arithmetics of the gf mesh_points :
the forwarding of the second argument was missing,
leading to subtle bugs e.g. in (in matrix case) :
deltaw(iom_) << iom_ * gw.singularity()(-1) + gw.singularity()(0) - gw(iom_);
because the partial evaluation of the expression introduced a dangling const matrix_view &
instead of moving the temporary matrix_view into the final matrix expression template.