# How to correctly refer arguments of macro in nested quote?
**URL:** https://discourse.julialang.org/t/how-to-correctly-refer-arguments-of-macro-in-nested-quote/23144
**Category:** General Usage
**Tags:** question
**Created:** [April 14, 2019, 5:45pm UTC](https://discourse.julialang.org/t/how-to-correctly-refer-arguments-of-macro-in-nested-quote/23144 "2019-04-14T17:45:14Z")
**Posts on this page:** 6
**Page:** 1
### Author:  [@shipengcheng1230](https://discourse.julialang.org/u/shipengcheng1230)
#### Post date: [April 14, 2019, 5:45pm UTC](https://discourse.julialang.org/t/how-to-correctly-refer-arguments-of-macro-in-nested-quote/23144/1 "2019-04-14T17:45:14Z")
Suppose I just want to do something like `f(x, ind) = x[ind] = 5.0`, I could write a similar macro like this:
```julia
julia> macro foo1(data, index)
esc(quote
$data[$index] = 5.0
end)
end
@foo1 (macro with 1 method)
julia> d1 = zeros(10);
julia> @foo1(d1, 3)
5.0
julia> d1[3] == 5
true
```
However, if I want some intermediate variable involved in it, like:
```julia
function foo2(data, index)
newindex = index * 2 # or other types of manipulation
data[newindex] = 5.0
end
```
I try to write the following:
```julia
julia> macro foo2(data, index)
newindex = gensym(:newindex)
esc(quote
$(newindex) = $(index) * 2
quote
$$(data)[$$(newindex)] = 5.0
end
end)
end
@foo2 (macro with 1 method)
julia> d2 = zeros(10);
julia> @macroexpand @foo2(d2, 3)
quote
#= REPL[16]:4 =#
##newindex#365 = 3 * 2
#= REPL[16]:5 =#
(Core._expr)(:block, $(QuoteNode(:(#= REPL[16]:6 =#))), (Core._expr)(:(=), (Core._expr)(:ref, d2, ##newindex#365), 5.0))
end
```
Notice that the final expr has `d2` in it instead of `:d2`, which the later is what I want. This isn’t setting the `d2` actually. How can I achieve this? I checked [this post](https://discourse.julialang.org/t/macro-hygiene-in-nested-quote-not-working/17806) but it doesn’t deal with this situation.
Thanks!
---
### Author:  [@shipengcheng1230](https://discourse.julialang.org/u/shipengcheng1230)
#### Post date: [April 14, 2019, 10:54pm UTC](https://discourse.julialang.org/t/how-to-correctly-refer-arguments-of-macro-in-nested-quote/23144/2 "2019-04-14T22:54:27Z")
I just solve this by following:
```julia
julia> macro foo4(data, index)
quote
newindex = $index * 2
$(data)[newindex] = 5.0
end
end
@foo4 (macro with 1 method)
julia> d3 = zeros(10);
julia> @foo4(d3, 3)
5.0
julia> d3[6] == 5.0
true
```
where I got a great help from [this tutorial](https://riptutorial.com/julia-lang/example/24364/quotenode--meta-quot--and-expr--quote-).
---
### Author:  [@Tamas\_Papp](https://discourse.julialang.org/u/Tamas_Papp)
#### Post date: [April 15, 2019, 5:08am UTC](https://discourse.julialang.org/t/how-to-correctly-refer-arguments-of-macro-in-nested-quote/23144/3 "2019-04-15T05:08:22Z")
> [@shipengcheng1230](#):
>
> do something like `f(x, ind) = x[ind] = 5.0` , I could write a similar macro
I may be missing something, but you don’t need a macro for this.
---
### Author:  [@shipengcheng1230](https://discourse.julialang.org/u/shipengcheng1230)
#### Post date: [April 15, 2019, 1:42pm UTC](https://discourse.julialang.org/t/how-to-correctly-refer-arguments-of-macro-in-nested-quote/23144/4 "2019-04-15T13:42:04Z")
I was trying to implement a callback function to incrementally write the output to a hdf5 file in DifferentialEquations.jl, hence I need a macro to generate that function (binded with some static variable by using `let`). So this is one of the ingredients where it came from.
---
### Author:  [@Tamas\_Papp](https://discourse.julialang.org/u/Tamas_Papp)
#### Post date: [April 15, 2019, 2:32pm UTC](https://discourse.julialang.org/t/how-to-correctly-refer-arguments-of-macro-in-nested-quote/23144/5 "2019-04-15T14:32:07Z")
I still don’t see why you need a macro, instead of a callable `struct` or closure.
---
### Author:  [@shipengcheng1230](https://discourse.julialang.org/u/shipengcheng1230)
#### Post date: [April 16, 2019, 12:56am UTC](https://discourse.julialang.org/t/how-to-correctly-refer-arguments-of-macro-in-nested-quote/23144/6 "2019-04-16T00:56:37Z")
You are right, I seem to make the problem more complicated. Nevertheless, this “detour” actually makes me learn something else.