# Are the Symbolics.jl docs outdated?
**URL:** https://discourse.julialang.org/t/are-the-symbolics-jl-docs-outdated/135212
**Category:** New to Julia
**Created:** [January 22, 2026, 11:48pm UTC](https://discourse.julialang.org/t/are-the-symbolics-jl-docs-outdated/135212 "2026-01-22T23:48:14Z")
**Posts on this page:** 6
**Page:** 1
### Author:  [@twcawm](https://discourse.julialang.org/u/twcawm)
#### Post date: [January 22, 2026, 11:48pm UTC](https://discourse.julialang.org/t/are-the-symbolics-jl-docs-outdated/135212/1 "2026-01-22T23:48:14Z")
I’m relatively new to Julia and have been having some trouble following the docs for Symbolics.jl ; not sure if I am misunderstanding something.
(I am looking at the “stable” version of Symbolics.jl docs, in the “variables” section of the Manual; I couldn’t include a link in the post. Though this question also applies to the ? help docs in the REPL since the docs there look identical.)
Examples:
[`TermInterface.iscall`]
the “examples” section for `iscall` returns “false” on all their examples when I run them - if I apply Symbolics.value(…) or Symbolics.unwrap(…) to the arg, I can reproduce the intended returns. Is this from an outdated version of Symbolics or something else?
[`TermInterface.arguments`]
Likewise, the Examples section on `arguments` doesn’t work for me - I see “MethodError: no method matching arguments(::Num)”; and likewise, if I wrap the args in Symbolics.value(…), they work.
Am I missing something here, or are possibly some of these docs outdated? Any suggestions to a newcomer trying to become acquainted with Symbolics but a little disconcerted with some of the docs examples (or advice on when to trust docs etc)? Thanks!
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### Author:  [@ChrisRackauckas](https://discourse.julialang.org/u/ChrisRackauckas)
#### Post date: [January 23, 2026, 7:51am UTC](https://discourse.julialang.org/t/are-the-symbolics-jl-docs-outdated/135212/2 "2026-01-23T07:51:50Z")
> [@twcawm](#):
>
> iscall
@cryptic.ax looks like we missed a spot.
> [@twcawm](#):
>
> Am I missing something here, or are possibly some of these docs outdated? Any suggestions to a newcomer trying to become acquainted with Symbolics but a little disconcerted with some of the docs examples (or advice on when to trust docs etc)? Thanks!
all docs have something outdated. Just open an issue if you find something.
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### Author:  [@cryptic.ax](https://discourse.julialang.org/u/cryptic.ax)
#### Post date: [January 23, 2026, 8:24am UTC](https://discourse.julialang.org/t/are-the-symbolics-jl-docs-outdated/135212/3 "2026-01-23T08:24:21Z")
Yeah that docstring is wrong. Even Symbolics v6 didn’t support `iscall` on `Num`. The docstring is in `SymbolicUtils` and should use `@syms`.
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### Author:  [@twcawm](https://discourse.julialang.org/u/twcawm)
#### Post date: [January 24, 2026, 9:33pm UTC](https://discourse.julialang.org/t/are-the-symbolics-jl-docs-outdated/135212/4 "2026-01-24T21:33:27Z")
thanks so much.
edit: I asked a question about not being able to find @register\_derivative, but then I realized it’s quite new and I had a slightly outdated version of Symbolics.
I guess you can really make things weird with something like
`@register_derivative sin(x) 1 exp(x)`
wonder if there is any use case for such things (or not).
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### Author:  [@cryptic.ax](https://discourse.julialang.org/u/cryptic.ax)
#### Post date: [January 30, 2026, 1:00pm UTC](https://discourse.julialang.org/t/are-the-symbolics-jl-docs-outdated/135212/5 "2026-01-30T13:00:22Z")
`@register_derivative` is for defining custom derivatives for functions you own. Implementing it for others’ functions is type-piracy. Specifically for `sin(x)`, this will also break precompilation due to method overwriting, since Symbolics already defines the `@register_derivative` for `sin(x)`
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### Author:  [@twcawm](https://discourse.julialang.org/u/twcawm)
#### Post date: [January 30, 2026, 8:06pm UTC](https://discourse.julialang.org/t/are-the-symbolics-jl-docs-outdated/135212/6 "2026-01-30T20:06:27Z")
OK. I am not sure if I understand the “break precompilation” statement; I can run this:
```julia-auto
julia> @register_derivative sin(x) 1 exp(x)
julia> Dx = Differential(x)
Differential(x, 1)
julia> Dx(sin(x))
Differential(x, 1)(sin(x))
julia> expand_derivatives(Dx(sin(x)))
exp(x)
julia> sin
sin (generic function with 21 methods) #showing this is the builtin
```
in any case, the first example in the @register\_derivative docstring uses the sin(x) example and doesn’t warn against this, which encouraged me to try it out with already registered functions.
Or perhaps do you mean that if I were to do this in a package, then precompiling that package would fail?
In any case thanks so much for the helpful clarifications!
>