I would like to be able to modify the Fundiff procedure from the Physics package to generalise it for my application by relaxing some of the constraints and changing to arbitrary direction rather than just a Dirac delta function.

In order to view the code, I write:

interface(verboseproc = 2);
print(Fundiff);

I then copied the code in order to modify it. However, there appear to be some functions that I do not have access to, including Tensor and TensorSort....