# An confused error for the Marco for Expr to function
**URL:** https://discourse.julialang.org/t/an-confused-error-for-the-marco-for-expr-to-function/40485
**Category:** General Usage
**Created:** [May 30, 2020, 9:56pm UTC](https://discourse.julialang.org/t/an-confused-error-for-the-marco-for-expr-to-function/40485 "2020-05-30T21:56:31Z")
**Posts on this page:** 5
**Page:** 1
### Author:  [@gangchern](https://discourse.julialang.org/u/gangchern)
#### Post date: [May 30, 2020, 9:56pm UTC](https://discourse.julialang.org/t/an-confused-error-for-the-marco-for-expr-to-function/40485/1 "2020-05-30T21:56:32Z")
I try to use the macro
```julia
macro expr2fn(fname, expr, args...)
fn = quote
function $(esc(fname))()
$(esc(expr.args[1]))
end
end
for arg in args
push!(fn.args[2].args[1].args, esc(arg))
end
return fn
end
```
Then I use :
@expr2fn(f, :((n1+n2+n3)), n1, n2, n3 )
f(0.1,0.2,0.3)
This is fine.
When I use like :
expr2=:((n1+n2+n3))
@expr2fn(test2\_func, expr2, n1, n2, n3 )
It generate an error
> Blockquote
> LoadError: type Symbol has no field args
> in expression starting at /Users/gangchen/Downloads/sample.jl:92
> getproperty(::Symbol, ::Symbol) at sys.dylib:?
> @expr2fn(::LineNumberNode, ::Module, ::Any, ::Any, ::Vararg{Any,N} where N) at sample.jl:65
> #macroexpand#32 at expr.jl:107 [inlined]
> (::Base.var"#kw##macroexpand")(::NamedTuple{(:recursive,),Tuple{Bool}}, ::typeof(macroexpand), ::Module, ::Expr) at none:0
> top-level scope at sample.jl:92
> include\_string(::Module, ::String, ::String) at sys.dylib:?
> include\_string(::Module, ::String, ::String, ::Int64) at eval.jl:30
> (::Atom.var"#188#192"{String,Int64,String,Bool})() at eval.jl:111
> withpath(::Atom.var"#188#192"{String,Int64,String,Bool}, ::String) at utils.jl:30
> withpath(::Function, ::String) at eval.jl:9
> #187 at eval.jl:110 [inlined]
> with\_logstate(::Atom.var"#187#191"{String,Int64,String,Bool}, ::Base.CoreLogging.LogState) at logging.jl:395
> with\_logger at logging.jl:491 [inlined]
> #186 at eval.jl:109 [inlined]
> hideprompt(::Atom.var"#186#190"{String,Int64,String,Bool}) at repl.jl:140
> macro expansion at eval.jl:108 [inlined]
> macro expansion at dynamic.jl:24 [inlined]
> eval(::String, ::Int64, ::String, ::String, ::Bool) at eval.jl:105
> macro expansion at eval.jl:39 [inlined]
> (::Atom.var"#172#173")() at task.jl:333
Any one know what happens and how to fix the problem?
---
### Author:  [@yuyichao](https://discourse.julialang.org/u/yuyichao)
#### Post date: [May 30, 2020, 10:13pm UTC](https://discourse.julialang.org/t/an-confused-error-for-the-marco-for-expr-to-function/40485/2 "2020-05-30T22:13:56Z")
It is impossible for macro to read from a runtime variable. If the value is know before runtime, just use the first one.
Even better, remove the quote from that argument.
---
### Author:  [@stevengj](https://discourse.julialang.org/u/stevengj)
#### Post date: [May 30, 2020, 10:16pm UTC](https://discourse.julialang.org/t/an-confused-error-for-the-marco-for-expr-to-function/40485/3 "2020-05-30T22:16:41Z")
Standard question: What are you trying to accomplish using a macro here? Are you passing expressions as arguments and using metaprogramming when you could pass function arguments instead?
---
### Author:  [@gangchern](https://discourse.julialang.org/u/gangchern)
#### Post date: [May 31, 2020, 4:31am UTC](https://discourse.julialang.org/t/an-confused-error-for-the-marco-for-expr-to-function/40485/4 "2020-05-31T04:31:51Z")
Yes. An additional question, are there any method can transform Julia expr to a function? We hope it can be used in REPL and in functions.
---
### Author:  [@stevengj](https://discourse.julialang.org/u/stevengj)
#### Post date: [May 31, 2020, 3:07pm UTC](https://discourse.julialang.org/t/an-confused-error-for-the-marco-for-expr-to-function/40485/5 "2020-05-31T15:07:55Z")
> [@gangchern](#):
>
> > [@stevengj](#):
> >
> > Are you passing expressions as arguments and using metaprogramming when you could pass function arguments instead?
>
> Yes.
Assuming your “yes” referred to my question: don’t use expressions to pass functions. Use functions to pass functions.
> [@gangchern](#):
>
> We hope it can be used in REPL and in functions.
What are you trying to accomplish? I think we may have an [XY problem](https://en.wikipedia.org/wiki/XY_problem) here.