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0 votes

I tried this example from the site:
https://cadabra.science/manual/PartialDerivative.html

\tau::Coordinate;
\partial{#}::Derivative(\tau);
f::Depends(\tau);
ex:= \partial{f g};
unwrap(ex);

It returns 0 instead of g∂f

asked in Bug reports by (160 points)

1 Answer

+1 vote

The above works fine with the current version on github. If it does not for you,
either upgrade, or say explicitly that the derivative is with respect to $\tau$,

  ex:= \partial_{\tau}{ f g};

or make $f$ depend on \partial:

 f::Depends(\partial{#}).

Otherwise the 'old' version of Cadabra which you use does not know how to figure out that \partial is a $\tau$-derivative.

answered by (50.9k points)
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