Symbolically evaluating an in-place function

General Usage
2

Nevermind, I figured it out:

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