Print an Inert Head with additional labels

[Omar Z]

Hello,

I would like to define an inert head, say "H", such that H[tens,n] is printed as "H^n tens".

If I define

DefInertHead[H]

PrintAs[H]^="H"

I have that, for example, H[tens,2] is printed as "H tens".

I know that it should be possible because the command Perturbation[tens,2] in xPert correctly prints the second argument as a power. The H head that I define also has most of the properties of Perturbation, eg it satisfies Leibnitz, if it can be useful. I tried to understand how it was done for Perturbation, but I did not get it.

Options to print with any other type of additional labels would also be appreciated.

Thank you in advance

Omar

[Thomas Bäckdahl]

Hi!

You can modify the more advanced display properties by changing the corresponding MakeBoxes command.
To tell Mathematica that you want your special code to be used instead of the standard code, you have to turn off the standard code before and turn it on again after your change.
For instance:
DefInertHead[He, PrintAs -> "H"]
xTensorFormStop[InertHead]
MakeBoxes[He[expr_, n_], StandardForm] :=
  xAct`xTensor`Private`interpretbox[He[expr, n],
   RowBox[{SuperscriptBox[PrintAs[Unevaluated[He]], PrintAs[n]], "[",
     MakeBoxes[expr, StandardForm], "]"}]];
xTensorFormStart[InertHead]

If you don't want the brackets, you can easily remove them in the lines above.

To have best control I would recommend that you implement your Leibnitz rules yourself either as rules that you apply when you need them or as UpValues for automatic rules.

Regards
Thomas

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[Omar Z]

Thank you very much, your help is very appreciated.

Omar