posftix notation for valence 0 tensors

[David Kofroň]

Dear xAct developers,
 a student asked me to help him with the following problem:

 It is possible to choose a postfix notation for covariant derivative by the assignment
$CovDFormat = "Postfix";

 alas, this does not work for valence 0 tensors, even in the latest xTensor version 1.2.0. See the minimal notebook attached, the very last line.

 It would have been nice, for the sake of consistency, to have all the derivatives in the postfix notation.

 Any help would be appreciated; but, being merely an aesthetic problem, it does not deserve too much attention (at least during the summer vacation period :) ).

 best regards

David Kofron

[Thomas Bäckdahl]

Hi!

This seems to be a bug. I usually don't use postfix notation, so I had not noticed.

There seems to be something missing in the function MakeBoxesCovD in xTensor.
Adding the following line to your code seems to fix the problem

xAct`xTensor`Private`MakeBoxesCovD[der_[i_ /; Head[i] =!= Dir][head_],"Postfix"] :=
  Block[{$WarningFrom = "CovD Formatting"}, SubsuperscriptBox[head, #1, #2] & @@xAct`xTensor`Private`AddIndex[{"", ""}, i, der]];

I hope Jose can add something like this to the next release.

Regards
Thomas

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[Ron Riegert]

I asked about this almost 3 years ago, but never got a response:

https://groups.google.com/g/xact/c/wHxrWsXduXw/m/K1OoqVm-AQAJ

[Jose]

Hi,

Yes, I'll fix this.

Thanks all for the reports and suggested fix.

Cheers,

Jose.