super(tensor);
}
@Override
public TraverseState next() {
TraverseState oldState = state();
Tensor oldTensor = tensor();
TraverseState newState = super.next();
Tensor newTensor = tensor();
if (oldState == TraverseState.Entering && oldTensor instanceof TensorField)
currentUpperProduct = new TensorReference(currentUpperProduct);
if (oldState == TraverseState.Entering && oldTensor instanceof Derivative) {