# Symbolically evaluating an in-place function

**URL:** <https://discourse.julialang.org/t/symbolically-evaluating-an-in-place-function/107264>\
**Category:** General Usage\
**Tags:** symbolics\
**Created:** [December 7, 2023, 10:41am UTC](https://discourse.julialang.org/t/symbolically-evaluating-an-in-place-function/107264 "2023-12-07T10:41:48Z")\
**Posts on this page:** 1\
**Showing post:** 2

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**Author:** ![Neodym](https://avatars.discourse-cdn.com/v4/letter/n/ba8739/32.png) [@Neodym](https://discourse.julialang.org/u/Neodym)\
**Post date:** [December 7, 2023, 11:03am UTC](https://discourse.julialang.org/t/symbolically-evaluating-an-in-place-function/107264/2 "2023-12-07T11:03:31Z")

</div>

Nevermind, I figured it out:

```julia
using Symbolics
@variables x[1:2] y[1:2]

function f!(result, arg)
    result[1] = arg[1] + 2
    result[2] = 2 * arg[2] + arg[1]
    nothing
end

yy = collect(y)
f!(yy, x)

```

This gives

```julia
julia> yy
2-element Vector{Num}:
     2 + x[1]
 x[1] + 2x[2]

```

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