# Can I invoke Julia's built-in type inference on a subarray{Any}?
**URL:** https://discourse.julialang.org/t/can-i-invoke-julias-built-in-type-inference-on-a-subarray-any/1985
**Category:** General Usage
**Created:** [February 8, 2017, 2:06pm UTC](https://discourse.julialang.org/t/can-i-invoke-julias-built-in-type-inference-on-a-subarray-any/1985 "2017-02-08T14:06:31Z")
**Posts on this page:** 4
**Page:** 1
### Author:  [@NickNack](https://discourse.julialang.org/u/NickNack)
#### Post date: [February 8, 2017, 2:06pm UTC](https://discourse.julialang.org/t/can-i-invoke-julias-built-in-type-inference-on-a-subarray-any/1985/1 "2017-02-08T14:06:31Z")
Given this:
```julia
julia> mat = [1 2; 3.0 4.0; 5 6.0; "seven" "eight"; :nine :ten]
4×2 Array{Any,2}:
1 2
3.0 4.0
5 6.0
"seven" "eight"
:nine :ten
julia> typeof(mat[1,1])
Int64
julia> typeof(mat[2,1])
Float64
julia> typeof(mat[1,:])
Array{Any,1}
julia> typeof(mat[2,:])
Array{Any,1}
```
Is there a built-in function somewhere, let’s call it `typeinfer()`, that can do this?
```julia
julia> typeinfer(mat[1,:])
Array{Int64,1}
julia> typeinfer(mat[2,:])
Array{Float64,1}
julia> typeinfer(mat[3,:])
Array{Float64,1}
julia> typeinfer(mat[4,:])
Array{String,1}
julia> typeinfer(mat[5,:])
Array{Symbol,1}
```
Or do I have to roll my own?
---
### Author:  [@mauro3](https://discourse.julialang.org/u/mauro3)
#### Post date: [February 8, 2017, 2:11pm UTC](https://discourse.julialang.org/t/can-i-invoke-julias-built-in-type-inference-on-a-subarray-any/1985/2 "2017-02-08T14:11:38Z")
The type cannot be inferred because the container has element type `Any`. So it will have to be a runtime check, which (I suspect) you have to write yourself.
---
### Author:  [@dpsanders](https://discourse.julialang.org/u/dpsanders)
#### Post date: [February 8, 2017, 3:11pm UTC](https://discourse.julialang.org/t/can-i-invoke-julias-built-in-type-inference-on-a-subarray-any/1985/3 "2017-02-08T15:11:59Z")
How about this:
```julia
julia> [mat[1, :]...]
2-element Array{Int64,1}:
1
2
julia> v = [[mat[i,:]...] for i in 1:size(mat, 1)]
5-element Array{Array{T,1},1}:
[1,2]
[3.0,4.0]
[5.0,6.0]
String["seven","eight"]
Symbol[:nine,:ten]
julia> v[1]
2-element Array{Int64,1}:
1
2
julia> v[2]
2-element Array{Float64,1}:
3.0
4.0
```
But the real question is why would you store things like that in the first place?
---
### Author:  [@NickNack](https://discourse.julialang.org/u/NickNack)
#### Post date: [February 8, 2017, 3:34pm UTC](https://discourse.julialang.org/t/can-i-invoke-julias-built-in-type-inference-on-a-subarray-any/1985/4 "2017-02-08T15:34:43Z")
> [@dpsanders](#):
>
> How about this:
>
> ```julia
> julia> [mat[1, :]...]
> 2-element Array{Int64,1}:
> 1
> 2
>
> ```
Brilliant! Why didn’t I think of trying a splat? Thanks!!
> [@](#):
>
> But the real question is why would you store things like that in the first place?
It’s a small part of a large optimization model (using JuMP). I have a macro that reads an external table of variable names and data and creates those variables in the local scope. And now I wanted to identify the type as well.
I know this setup would be absolutely horrible for ordinary coding projects, but for optimization the focus is on the equations, so the hack is fine. Probably. 🙂