# Undef for non-arrays
**URL:** https://discourse.julialang.org/t/undef-for-non-arrays/69250
**Category:** General Usage
**Created:** [October 5, 2021, 6:48pm UTC](https://discourse.julialang.org/t/undef-for-non-arrays/69250 "2021-10-05T18:48:32Z")
**Posts on this page:** 7
**Page:** 1
### Author:  [@goerch](https://discourse.julialang.org/u/goerch)
#### Post date: [October 5, 2021, 6:48pm UTC](https://discourse.julialang.org/t/undef-for-non-arrays/69250/1 "2021-10-05T18:48:32Z")
Do we have something similar to undef for non-arrays? Wishful thinking:
```julia
f() = a::Tuple{Int, Int} where T = 5, undef
```
---
### Author:  [@Mason](https://discourse.julialang.org/u/Mason)
#### Post date: [October 5, 2021, 7:08pm UTC](https://discourse.julialang.org/t/undef-for-non-arrays/69250/2 "2021-10-05T19:08:08Z")
Could you explain what you want that to do?
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### Author:  [@goerch](https://discourse.julialang.org/u/goerch)
#### Post date: [October 5, 2021, 7:16pm UTC](https://discourse.julialang.org/t/undef-for-non-arrays/69250/3 "2021-10-05T19:16:20Z")
I’m trying to implement node allocators, which could make use of undefined memory like arrays do.
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### Author:  [@Mason](https://discourse.julialang.org/u/Mason)
#### Post date: [October 5, 2021, 7:21pm UTC](https://discourse.julialang.org/t/undef-for-non-arrays/69250/4 "2021-10-05T19:21:16Z")
You could use a `Ref`, e.g. `Ref{Tuple{Int, Int}}()` will be a mutable container that can be updated later.
Or you could use StaticArrays.jl’s `MVector`. e.g. `MVector{2, Int}(undef)`.
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### Author:  [@goerch](https://discourse.julialang.org/u/goerch)
#### Post date: [October 5, 2021, 7:39pm UTC](https://discourse.julialang.org/t/undef-for-non-arrays/69250/5 "2021-10-05T19:39:34Z")
`Ref{Tuple{Int, Int}}()` I understand, but if we have a vector of these there a probably some allocations required.
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### Author:  [@Mason](https://discourse.julialang.org/u/Mason)
#### Post date: [October 5, 2021, 8:01pm UTC](https://discourse.julialang.org/t/undef-for-non-arrays/69250/6 "2021-10-05T20:01:30Z")
If you have a vector of them then you just use `undef`.
```julia
julia> v = Vector{Tuple{Int, Int}}(undef, 2)
2-element Vector{Tuple{Int64, Int64}}:
(9, 4)
(11, 5)
```
---
### Author:  [@goerch](https://discourse.julialang.org/u/goerch)
#### Post date: [October 10, 2021, 3:15pm UTC](https://discourse.julialang.org/t/undef-for-non-arrays/69250/7 "2021-10-10T15:15:51Z")
Just noticed [Create a struct with uninitialized fields - #5 by dfdx](https://discourse.julialang.org/t/create-a-struct-with-uninitialized-fields/6967/5) in the feed.