I want to assign a certain value to an element of a tensor. This element is identified by an array obtained from some evaluations, so we fix it. Here i present an oversimplified core part of my code:

DimensionA = 3;
v = {1, 2, 3};
Array[TensorA, Table[10, DimensionA], 0];  
TensorA @@ v = 12;

at this point i receive an error

Set::write: Tag Apply in TensorA@@{1,2,3} is Protected.

Obviously if i do TensorA[1, 2, 3] = 12; it is all ok, but my aim is to give in input a vector with an arbitrary number of indices. Please show me how I should input the vector to the tensor without receiving this error.

  • 1
    $\begingroup$ Note that half the code in this question is extraneous. v = {1, 2, 3}; Evaluate[TensorA @@ v] = 12 is sufficient to set TensorA[1, 2, 3] to 12. $\endgroup$
    – bbgodfrey
    Oct 7, 2018 at 17:31
  • $\begingroup$ Thank you, here there is good related answer right here : mathematica.stackexchange.com/questions/183259/… $\endgroup$ Oct 7, 2018 at 20:25
  • $\begingroup$ I wrote it but did not post a similar answer here, because it would have been the same as the one by @ThatGravityGuy. Thank you for the kind words. $\endgroup$
    – bbgodfrey
    Oct 7, 2018 at 20:39

1 Answer 1


Just force the Apply before Set.

Evaluate[TensorA @@ v] = 12

Also for the dimensions specification Table[10, DimensionA], I suggest using ConstantArray[10, DimensionA] instead.


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