Question: Bug in Physics metric?

Hi all,

I found some strange behavior while usings tensors from Physics; I wanted to make sure I wasn't missing something here.

It seems that changing the metric (for instance, to +++-) causes raising and lowering problems. As an example:

with(Physics):
Setup(metric=`+++-`):

# Define our system of equations
Coordinates(X):

# Define tensors
{U[~mu] = [u(X),0,0,1],
A[~mu]=[0,0,0,n(X)]}:
Define(op(%)):

F[mu,nu]=d_[mu](A[nu]) - d_[nu](A[mu]):
Define(%):

# Multiply tensors
TensorArray(F[~0,~mu].U[mu]);

This produces

-diff(n(X),x1)*u(X)-2*diff(n(X),x4)

However, only the first term should be present. It seems that changing the mulitplication to F[0,~mu].U[mu] produces the correct output, as does removing the Setup call. Also, manually defining F produces the expected output; only defining it via A seems to generate the discrepancy.

Any idea if this is a bug or a feature?

Thanks!