How to make ParamD to commute with partial derivative?

[Júnior Diniz Toniato]

Dear all,

I'm learning to work with mathematica and xTensor package. 

I would like to know if it is possible to make ParamD and PD to comute.

My PD has been defined together with a flat metric:

DefMetric[1, \[Delta][-i, -j], PD, {",", "\[PartialD]"}, 

  FlatMetric -> True, PrintAs -> "\[Delta]"];

And I have a parameter t: 

DefParameter[t]

Now, I want that mathematica understands that

ParamD[t][PD[-i][X]]

is the same as

PD[-i][ParamD[t][X]],

where X can be any tensor with 0, 1 or 2 indices.

Thanks for your time.

[ghadir jafari]

Hi Toniato

You can set this as follows:

Unprotect[PD];

ParamD[t]@PD[-i_]@A_ := PD[-i]@ParamD[t]@A

Protect[PD];

[Júnior Diniz Toniato]

Thank you, Jafari.

It worked fine.