# How to replace macro argument with expr as being typed manually?
**URL:** https://discourse.julialang.org/t/how-to-replace-macro-argument-with-expr-as-being-typed-manually/26630
**Category:** New to Julia
**Tags:** question
**Created:** [July 22, 2019, 1:56pm UTC](https://discourse.julialang.org/t/how-to-replace-macro-argument-with-expr-as-being-typed-manually/26630 "2019-07-22T13:56:30Z")
**Posts on this page:** 6
**Page:** 1
### Author:  [@Islam0mar](https://discourse.julialang.org/u/Islam0mar)
#### Post date: [July 22, 2019, 1:56pm UTC](https://discourse.julialang.org/t/how-to-replace-macro-argument-with-expr-as-being-typed-manually/26630/1 "2019-07-22T13:56:30Z")
Given a macro `@NLobjective` which have the following usage example: `@NLobjective(m, Min, 11 x² - 484 x + 12358)`
I want to write a function that returns the last expression `11 x² - 484 x + 12358`.
Function implementation:
```julia
function CreateEq(x::VariableRef, arr::Array)
s = 0
for i in arr
s += (x-i)^2
end
return :(@NLobjective(m, Min, begin $(s) end))
end
```
given x and `S = [5,6,7,9,11,16,20,22,23,24,99]`
Output from `eval(CreateEq(x,S))` is understood in a different way that writing `@NLobjective(m, Min, 11 x² - 484 x + 12358)` and gives the following error message:
> ERROR: Unexpected quadratic expression 11 x² - 484 x + 12358 in nonlinear expression. Quadratic expressions (e.g., created using @expression) and nonlinear expressions cannot be mixed.
Questions:
- How to make `begin $(s) end` be substituted as manually writing `11 x² - 484 x + 12358`?
---
### Author:  [@odow](https://discourse.julialang.org/u/odow)
#### Post date: [July 22, 2019, 2:42pm UTC](https://discourse.julialang.org/t/how-to-replace-macro-argument-with-expr-as-being-typed-manually/26630/2 "2019-07-22T14:42:50Z")
What are you trying to achieve? There is probably a better way to do it.
Do you want something like?
```nohighlight
function create_eq(model, x, arr)
return @expression(model, sum((x - i)^2 for i in arr))
end
```
---
### Author:  [@Islam0mar](https://discourse.julialang.org/u/Islam0mar)
#### Post date: [July 22, 2019, 2:48pm UTC](https://discourse.julialang.org/t/how-to-replace-macro-argument-with-expr-as-being-typed-manually/26630/3 "2019-07-22T14:48:20Z")
I want to get around this setup:
```julia
my_expr = CreateEq(x,S)
@variable(m, aux)
@constraint(m, aux == my_expr)
```
I have tried your function using this: `@NLobjective(m, Min, @eval(create_eq(m,x,S)))`, but it gives the same error
---
### Author:  [@odow](https://discourse.julialang.org/u/odow)
#### Post date: [July 22, 2019, 3:41pm UTC](https://discourse.julialang.org/t/how-to-replace-macro-argument-with-expr-as-being-typed-manually/26630/4 "2019-07-22T15:41:08Z")
So I assume you want to include an affine or quadratic expression within a nonlinear objective? And you followed the work-around in the docs? [Nonlinear Modeling · JuMP](http://www.juliaopt.org/JuMP.jl/v0.19.2/nlp/#Syntax-notes-1)
At present, the work-around is recommended:
```nohighlight
function create_eq(model, x, arr)
aux = @variable(model)
@constraint(model, aux == sum((x - i)^2 for i in arr))
return aux
end
model = Model()
@variable(model, x)
ex = create_eq(model, x, [1, 2, 3])
@NLobjective(model, Min, ex)
```
Also, please read [Please read: make it easier to help you](https://discourse.julialang.org/t/psa-make-it-easier-to-help-you/14757), and provide a minimal working example.
---
### Author:  [@Islam0mar](https://discourse.julialang.org/u/Islam0mar)
#### Post date: [July 23, 2019, 3:59am UTC](https://discourse.julialang.org/t/how-to-replace-macro-argument-with-expr-as-being-typed-manually/26630/5 "2019-07-23T03:59:59Z")
Yes, that is it.
Thanks I will use your solution.
---
### Author:  [@Islam0mar](https://discourse.julialang.org/u/Islam0mar)
#### Post date: [July 24, 2019, 4:20am UTC](https://discourse.julialang.org/t/how-to-replace-macro-argument-with-expr-as-being-typed-manually/26630/6 "2019-07-24T04:20:22Z")
Here is the solution:
```nohighlight
function CreateEq(x::VariableRef, arr::Array)
s = Expr(:call,:+)
for i in arr
push!(s.args, :((x - $i)^2))
end
return s
end
```
call it like that for macros:
```julia
eval(:(@NLobjective(m, Min, $(CreateEq(x,S)))))
```