# Symbolic rewriter rules for symbolic functions

**URL:** <https://discourse.julialang.org/t/symbolic-rewriter-rules-for-symbolic-functions/123131>\
**Category:** General Usage\
**Tags:** symbolics, symbolic-utils, symbolicutils\
**Created:** [November 26, 2024, 11:55pm UTC](https://discourse.julialang.org/t/symbolic-rewriter-rules-for-symbolic-functions/123131 "2024-11-26T23:55:07Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![erny123](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/erny123/32/52255_2.png) [@erny123](https://discourse.julialang.org/u/erny123)\
**Post date:** [November 26, 2024, 11:55pm UTC](https://discourse.julialang.org/t/symbolic-rewriter-rules-for-symbolic-functions/123131/1 "2024-11-26T23:55:07Z")

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I have something simple that there seems to be no answer anywhere. I make a symbolic function and none of the re-writing rules work on it.

```julia
using SymbolicUtils
using Symbolics
using Latexify
using Plots
using LaTeXStrings
using SymbolicUtils.Rewriters

@variables x t Tinv(..) 

test = Tinv(x) 

r = @rule Tinv(~a) => ~a/2
r2 = @rule Tinv(~~a) =>~~a/2

r(test) #returns nothing
r(Symbolics.value(test)) #returns nothing
r(test.val) #returns nothing

r2(test) #returns nothing
r2(Symbolics.value(test)) #returns nothing
r2(test.val) #returns nothing

simplify(test, rewriter=r) # returns test unmodified
simplify(test.val, rewriter=r) # returns test unmodified
simplify(Symbolics.value(test), rewriter=r) #returns test unmodified

#similar when using r2

```

So what’s the issue and why isn’t there compatibility with the SymbolicUtils.jl rewriting functions?

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<div class="post-metadata">

**Author:** ![ChrisRackauckas](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/chrisrackauckas/32/77_2.png) [@ChrisRackauckas](https://discourse.julialang.org/u/ChrisRackauckas)\
**Post date:** [November 28, 2024, 4:39pm UTC](https://discourse.julialang.org/t/symbolic-rewriter-rules-for-symbolic-functions/123131/2 "2024-11-28T16:39:38Z")

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It’s just a current issue. I believe someone has already recently opened an issue for it. It just needs bodies.

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<div class="post-metadata">

**Author:** ![erny123](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/erny123/32/52255_2.png) [@erny123](https://discourse.julialang.org/u/erny123)\
**Post date:** [November 28, 2024, 8:13pm UTC](https://discourse.julialang.org/t/symbolic-rewriter-rules-for-symbolic-functions/123131/3 "2024-11-28T20:13:42Z")

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Got it. I’ll try to find the issue on github and see where it’s at.