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Passing function to derivative results in zero #1085

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kapple19 opened this issue Mar 7, 2024 · 5 comments · May be fixed by #1257
Open

Passing function to derivative results in zero #1085

kapple19 opened this issue Mar 7, 2024 · 5 comments · May be fixed by #1257

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@kapple19
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kapple19 commented Mar 7, 2024

Not sure if this is a bug, but I think this should either throw an error or be fixed.

Setup:

using Symbolics: derivative
f(x) = x^2
@variables x

and then

derivative(f, x)

gives 0,

derivative(f(x), x)

gives Num(2x).

The former should error or be fixed, right?
@ChrisRackauckas
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Yes, we should make it error on non-Num or BasicSymbolic

@kapple19
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Would it be appropriate to try and feed x to f instead of erroring?

@ChrisRackauckas
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Yeah we can make a dispatch for ::Function that just feeds it in and then calls derivative. And then another catch-all dispatch for ::Any that checks if it's symbolic in some form and uses it, otherwise it errors saying derivative is not supported on typeof(f).

@kapple19
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kapple19 commented Sep 3, 2024

What do you mean by "symbolic in some form"? Is Complex{Num} an example?

@kapple19 kapple19 mentioned this issue Sep 3, 2024
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@ChrisRackauckas
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Union{Num, BasicSymbolic}

ChrisRackauckas added a commit that referenced this issue Sep 4, 2024
@ChrisRackauckas
Merge pull request #1256 from kapple19/#1085
69cf971 
Fix false positive result of passing a `Function` to `derivative`
@kapple19 kapple19 linked a pull request Sep 4, 2024 that will close this issue
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Added BasicSymbolic as input for function fed to derivative kapple19/Symbolics.jl
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@ChrisRackauckas @kapple19