# How can I improve this piece of code?

**URL:** https://discourse.julialang.org/t/how-can-i-improve-this-piece-of-code/81871
**Category:** New to Julia
**Tags:** question, struct, improvement
**Created:** [May 29, 2022, 3:16pm UTC](https://discourse.julialang.org/t/how-can-i-improve-this-piece-of-code/81871 "2022-05-29T15:16:59Z")
**Posts on this page:** 3
**Page:** 1

<div class="post-metadata">

### Author: ![vamp](https://avatars.discourse-cdn.com/v4/letter/v/f4b2a3/32.png) [@vamp](https://discourse.julialang.org/u/vamp)
#### Post date: [May 29, 2022, 3:16pm UTC](https://discourse.julialang.org/t/how-can-i-improve-this-piece-of-code/81871/1 "2022-05-29T15:16:59Z")

</div>

Hello,

I am new to Julia and I’m trying to do one of my first codes. I have created two _Structs_ that can be described as follows:

```julia
struct Struct1 
    a::Int
    b::SVector{value1, Int} 
    c::Int 
end 

struct Struct2 
    d::SVector{value1, Int}
end

```

I have the following function:

```julia
function MyFunction(x::Struct1)
    return [(Struct2(d)) for d in Iterators.product(0:value2.-x.b[1],0:value2.-x.b[2]) if sum(d)<=x.a]
end

```

It works when `value1 = 2`, but I want to know how can I put it so if `value1=4` it changes.

Thanks 🙂

---

<div class="post-metadata">

### Author: ![Henrique\_Becker](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/henrique_becker/32/15443_2.png) [@Henrique\_Becker](https://discourse.julialang.org/u/Henrique_Becker)
#### Post date: [May 29, 2022, 5:09pm UTC](https://discourse.julialang.org/t/how-can-i-improve-this-piece-of-code/81871/2 "2022-05-29T17:09:35Z")

</div>

You cannot have a `struct` dynamically change like that. What would happen with all the objects that had just two elements? They would gain two new undefined elements immediately? What you can do is to use a struct with type parameters, and so allow many different versions of the type with different lengths.

```julia
julia> using StaticArrays

julia> struct Struct1{N}
           a::Int
           b::SVector{N, Int} 
           c::Int 
       end

julia> struct Struct2{N}
           d::SVector{N, Int}
       end

julia> function MyFunction(x::Struct1{N}) where {N}
           return [(Struct2{N}(SVector{N}(d...))) for d in Iterators.product(ntuple((i -> 0:N .- x.b[i]), N)...) if sum(d)<=x.a]
       end

julia> MyFunction(Struct1{2}(1, SVector{2, Int}(1, 1), 1))
3-element Array{Struct2{2},1}:
 Struct2{2}([0, 0])
 Struct2{2}([1, 0])
 Struct2{2}([0, 1])

julia> MyFunction(Struct1{3}(1, SVector{3, Int}(1, 1, 1), 1))
4-element Array{Struct2{3},1}:
 Struct2{3}([0, 0, 0])
 Struct2{3}([1, 0, 0])
 Struct2{3}([0, 1, 0])
 Struct2{3}([0, 0, 1])

```

I assumed `value2` weas a mistake and you meant `value1`.

---

<div class="post-metadata">

### Author: ![vamp](https://avatars.discourse-cdn.com/v4/letter/v/f4b2a3/32.png) [@vamp](https://discourse.julialang.org/u/vamp)
#### Post date: [May 30, 2022, 11:35am UTC](https://discourse.julialang.org/t/how-can-i-improve-this-piece-of-code/81871/3 "2022-05-30T11:35:11Z")

</div>

Hello,

Yes, you are totally right. I am sorry, I am new and there are some things that I still don’t know.

Thank you so much for your help.