This could solve the issue https://github.com/sympy/sympy/issues/11444

*Expr.is_constant()* checks whether the expression derivative by its free 
symbols is nonzero. Unfortunately *A[i].diff(i)* currently gives 0.

Free symbols of *A[i]* are *A *and *i*.


On Thursday, 26 January 2017 17:04:01 UTC+1, Björn Dahlgren wrote:
>
>
> Do you have an applied example where this would help? If it simplifies 
> users' code I think that would be an argument for it.
>

 Not really, indices are supposed to be integers, the derivative doesn't 
make any sense. On the other hand integer symbols are still derivable in 
SymPy.

Furthermore, nothing forbids to use indexed objects as very strange 
functions.

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