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I have the code TensorDimensions[TensorContract[c, {{1, 2}}]]. It is in normal form. But if I add the rules:

Unprotect[TensorDimensions]
TensorDimensions[c] = {4, 4, 5}

then the code evaluates to {5}.

I was wondering, is there some specific language construct that would give me the result of the evaluation TensorDimensions[TensorContract[c, {{1, 2}}]] if I were to add those rules, without actually adding those rules in the global context?

I would like to see what would happen to the expression evaluation if the rules were added, but not add the rules. Is this possible? Like a "stronger" version of what ReplaceAll does.

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1 Answer 1

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Sounds like you want to use TensorReduce[] with assumptions:

Assuming[c ∈ Arrays[{4, 4, 5}],
        TensorReduce[TensorDimensions[TensorContract[c, {{1, 2}}]]]]
   {5}
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  • $\begingroup$ This works for the particular case of TensorDimensions , however I'm still wondering if it's possible to have a general construct that operates like I've described in my post. I've tried using contexts with Begin and End, but it turns out if you're in a context and add rules to a function that's already defined in the global context, the rules "leak out" to the global context. Block and Module don't seem to work as would be needed also. The 'Unset` function seems like the most helpful for this kind of construct, but it unsets everithing, not just locally added rules. $\endgroup$
    – user3257842
    May 3, 2020 at 2:00

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