# Run a macro on all code evaluated by julia
**URL:** https://discourse.julialang.org/t/run-a-macro-on-all-code-evaluated-by-julia/2633
**Category:** General Usage
**Created:** [March 13, 2017, 4:48am UTC](https://discourse.julialang.org/t/run-a-macro-on-all-code-evaluated-by-julia/2633 "2017-03-13T04:48:51Z")
**Posts on this page:** 6
**Page:** 1
### Author:  [@bramtayl](https://discourse.julialang.org/u/bramtayl)
#### Post date: [March 13, 2017, 4:48am UTC](https://discourse.julialang.org/t/run-a-macro-on-all-code-evaluated-by-julia/2633/1 "2017-03-13T04:48:51Z")
Let’s say I have a function that transforms julia code, and I want to prerun it on any code ever evaluated by Julia. Is there a way to do this? If not, it seems like a great way to customize the Julia experience
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### Author:  [@Tamas\_Papp](https://discourse.julialang.org/u/Tamas_Papp)
#### Post date: [March 13, 2017, 6:26am UTC](https://discourse.julialang.org/t/run-a-macro-on-all-code-evaluated-by-julia/2633/2 "2017-03-13T06:26:00Z")
What are you trying to achieve?
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### Author:  [@Per](https://discourse.julialang.org/u/Per)
#### Post date: [March 13, 2017, 9:09am UTC](https://discourse.julialang.org/t/run-a-macro-on-all-code-evaluated-by-julia/2633/3 "2017-03-13T09:09:43Z")
You could very easily create a macro `@c` so that any command prefixed with those two characters is subject to your customization. Apply this to an entire module with:
```julia
@c module my_module
lots of
customized
code
end
```
I don’t think most people would want to have a 100% transparent way of altering how julia works. Programmers like to be able to look at a piece of code and know what it does. Having to add at least two characters when you want your code parsed in your own fashion is a small price to pay for that. (The reason why macros calls are prefixed with the `@` character is to warn the reader to expect the unexpected.)
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### Author:  [@StefanKarpinski](https://discourse.julialang.org/u/StefanKarpinski)
#### Post date: [March 13, 2017, 1:51pm UTC](https://discourse.julialang.org/t/run-a-macro-on-all-code-evaluated-by-julia/2633/4 "2017-03-13T13:51:12Z")
This would not be terribly hard to insert into the REPL code. It’s a bit strange though. It would, of course, only be useful for syntactic transformations, but I can imagine using it, e.g., for backwards compatibility support.
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### Author:  [@bramtayl](https://discourse.julialang.org/u/bramtayl)
#### Post date: [March 13, 2017, 2:50pm UTC](https://discourse.julialang.org/t/run-a-macro-on-all-code-evaluated-by-julia/2633/5 "2017-03-13T14:50:57Z")
Said macro already exists, and inspired this thread!
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### Author:  [@bramtayl](https://discourse.julialang.org/u/bramtayl)
#### Post date: [March 13, 2017, 3:06pm UTC](https://discourse.julialang.org/t/run-a-macro-on-all-code-evaluated-by-julia/2633/6 "2017-03-13T15:06:04Z")
[https://github.com/JunoLab/Atom.jl/pull/79/files](https://github.com/JunoLab/Atom.jl/pull/79/files)
I’m sure something similar could be done for the REPL but this is good enough for me rn