# When I declare an empty array, what does the output given by the typeof method mean?
**URL:** https://discourse.julialang.org/t/when-i-declare-an-empty-array-what-does-the-output-given-by-the-typeof-method-mean/47546
**Category:** New to Julia
**Created:** [September 30, 2020, 4:53pm UTC](https://discourse.julialang.org/t/when-i-declare-an-empty-array-what-does-the-output-given-by-the-typeof-method-mean/47546 "2020-09-30T16:53:10Z")
**Posts on this page:** 18
**Page:** 1
### Author:  [@anon60034542](https://discourse.julialang.org/u/anon60034542)
#### Post date: [September 30, 2020, 4:53pm UTC](https://discourse.julialang.org/t/when-i-declare-an-empty-array-what-does-the-output-given-by-the-typeof-method-mean/47546/1 "2020-09-30T16:53:10Z")
When I declare an empty array and call `typeof()`, I get the following output:
```julia
numbers = []
println(typeof(numbers))
# Output:
Array{Any,1}
```
1. What does the `1` mean in this case? Does it mean it’s a one dimensional array?
2. Does the documentation present a clear way to declare an array?
---
### Author:  [@jishnub](https://discourse.julialang.org/u/jishnub)
#### Post date: [September 30, 2020, 4:59pm UTC](https://discourse.julialang.org/t/when-i-declare-an-empty-array-what-does-the-output-given-by-the-typeof-method-mean/47546/2 "2020-09-30T16:59:27Z")
Yes, the 1 means that it’s a one-dimensional array. In general the types of arrays are of the form `SomeArray{T,N}`, where `T` is the element type and `N` is the number of dimensions.
You may define arrays, for example, as
```julia
julia> Array{Int,2}(undef, 2, 2)
2×2 Array{Int64,2}:
0 0
0 0
```
where the `undef` specifies that the elements are undeclared, and the other arguments specify the sizes along each dimension.
---
### Author:  [@anon60034542](https://discourse.julialang.org/u/anon60034542)
#### Post date: [September 30, 2020, 5:07pm UTC](https://discourse.julialang.org/t/when-i-declare-an-empty-array-what-does-the-output-given-by-the-typeof-method-mean/47546/3 "2020-09-30T17:07:07Z")
If I wanted to define an empty array of `Ints` with zero elements, I can do this:
```julia
numbers = Array{Int,1}(undef, 0)
```
Is the initialization correct for an integer array with 0 elements?
and if I wanted to add elements I can do:
```julia
push!(numbers, 10,1,7,3)
```
---
### Author:  [@PetrKryslUCSD](https://discourse.julialang.org/u/PetrKryslUCSD)
#### Post date: [September 30, 2020, 5:07pm UTC](https://discourse.julialang.org/t/when-i-declare-an-empty-array-what-does-the-output-given-by-the-typeof-method-mean/47546/4 "2020-09-30T17:07:15Z")
You can also create an empty array like this:
```julia
a = Int[]
```
This one is typed to `Int`. As opposed to `Any`.
---
### Author:  [@anon60034542](https://discourse.julialang.org/u/anon60034542)
#### Post date: [September 30, 2020, 5:12pm UTC](https://discourse.julialang.org/t/when-i-declare-an-empty-array-what-does-the-output-given-by-the-typeof-method-mean/47546/5 "2020-09-30T17:12:59Z")
Thanks for the quick reply.
I forgot to hit reply before I posted my followup question, see below. It’s the one about declaring an empty one dimensional array of `Ints`
---
### Author:  [@anon60034542](https://discourse.julialang.org/u/anon60034542)
#### Post date: [September 30, 2020, 5:19pm UTC](https://discourse.julialang.org/t/when-i-declare-an-empty-array-what-does-the-output-given-by-the-typeof-method-mean/47546/6 "2020-09-30T17:19:23Z")
Is doing this also an acceptable way of declaring a `0` element, 1 dimensional array of `Ints`:
```julia
numbers = Array{Int,1}(undef, 0)
```
---
### Author:  [@simonbyrne](https://discourse.julialang.org/u/simonbyrne)
#### Post date: [September 30, 2020, 5:28pm UTC](https://discourse.julialang.org/t/when-i-declare-an-empty-array-what-does-the-output-given-by-the-typeof-method-mean/47546/7 "2020-09-30T17:28:48Z")
Yes, or you can even leave off the `1` since it is implicit from the size:
```julia
julia> numbers = Array{Int,1}(undef, 0)
Int64[]
julia> numbers = Array{Int}(undef, 0)
Int64[]
```
---
### Author:  [@DNF](https://discourse.julialang.org/u/DNF)
#### Post date: [September 30, 2020, 5:41pm UTC](https://discourse.julialang.org/t/when-i-declare-an-empty-array-what-does-the-output-given-by-the-typeof-method-mean/47546/8 "2020-09-30T17:41:12Z")
You can also use the alias `Vector`:
```julia
numbers = Vector{Int}()
```
---
### Author:  [@fredrikekre](https://discourse.julialang.org/u/fredrikekre)
#### Post date: [September 30, 2020, 6:44pm UTC](https://discourse.julialang.org/t/when-i-declare-an-empty-array-what-does-the-output-given-by-the-typeof-method-mean/47546/9 "2020-09-30T18:44:39Z")
My favorite: `getindex(Int)`.
---
### Author:  [@affans](https://discourse.julialang.org/u/affans)
#### Post date: [September 30, 2020, 7:51pm UTC](https://discourse.julialang.org/t/when-i-declare-an-empty-array-what-does-the-output-given-by-the-typeof-method-mean/47546/10 "2020-09-30T19:51:30Z")
There are also `zeros` and `fill` functions to generate arrays, as well as comprehensions and generators.
---
### Author:  [@Henrique\_Becker](https://discourse.julialang.org/u/Henrique_Becker)
#### Post date: [September 30, 2020, 8:19pm UTC](https://discourse.julialang.org/t/when-i-declare-an-empty-array-what-does-the-output-given-by-the-typeof-method-mean/47546/11 "2020-09-30T20:19:47Z")
> [@fredrikekre](#):
>
> My favorite: `getindex(Int)` .
I was really confused as why this would work, until I looked up the documentation:
```julia
getindex(type[, elements...])
Construct a 1-d array of the specified type. This is usually called with the
syntax Type[]. Element values can be specified using Type[a,b,c,...].
Examples
≡≡≡≡≡≡≡≡≡≡
julia> Int8[1, 2, 3]
3-element Array{Int8,1}:
1
2
3
julia> getindex(Int8, 1, 2, 3)
3-element Array{Int8,1}:
1
2
3
```
---
### Author:  [@ZhiyuanYao](https://discourse.julialang.org/u/ZhiyuanYao)
#### Post date: [May 3, 2021, 2:32am UTC](https://discourse.julialang.org/t/when-i-declare-an-empty-array-what-does-the-output-given-by-the-typeof-method-mean/47546/12 "2021-05-03T02:32:58Z")
This method is not mentioned in the official documentation. Is it guaranteed?
---
### Author:  [@jling](https://discourse.julialang.org/u/jling)
#### Post date: [May 3, 2021, 2:48am UTC](https://discourse.julialang.org/t/when-i-declare-an-empty-array-what-does-the-output-given-by-the-typeof-method-mean/47546/13 "2021-05-03T02:48:57Z")
the doc mentions `Vector{T}` is just an alias:
[https://docs.julialang.org/en/v1/base/arrays/#Base.Vector](https://docs.julialang.org/en/v1/base/arrays/#Base.Vector)
---
### Author:  [@ZhiyuanYao](https://discourse.julialang.org/u/ZhiyuanYao)
#### Post date: [May 3, 2021, 2:50am UTC](https://discourse.julialang.org/t/when-i-declare-an-empty-array-what-does-the-output-given-by-the-typeof-method-mean/47546/14 "2021-05-03T02:50:40Z")
Still the method `Array{T,1}()` is not documented. Or am I mising something?
---
### Author:  [@jling](https://discourse.julialang.org/u/jling)
#### Post date: [May 3, 2021, 3:05am UTC](https://discourse.julialang.org/t/when-i-declare-an-empty-array-what-does-the-output-given-by-the-typeof-method-mean/47546/15 "2021-05-03T03:05:28Z")
~~not sure what do you mean~~ , it’s documented here:
[https://docs.julialang.org/en/v1/base/arrays/#Core.Array-Tuple{UndefInitializer,%20Any}](https://docs.julialang.org/en/v1/base/arrays/#Core.Array-Tuple%7BUndefInitializer,%20Any%7D)
maybe you mean that `Array{T, 1}()` is the same as `Array{T,1}(undef, 0)` is not spelled out in the docs?
---
### Author:  [@ZhiyuanYao](https://discourse.julialang.org/u/ZhiyuanYao)
#### Post date: [May 3, 2021, 3:14am UTC](https://discourse.julialang.org/t/when-i-declare-an-empty-array-what-does-the-output-given-by-the-typeof-method-mean/47546/16 "2021-05-03T03:14:40Z")
Yes, exactly. I have not see a place where `Array{T, 1}()` pops out, only constructors such as `Array{T}(undef, dims)`.
---
### Author:  [@amrods](https://discourse.julialang.org/u/amrods)
#### Post date: [May 3, 2021, 3:16am UTC](https://discourse.julialang.org/t/when-i-declare-an-empty-array-what-does-the-output-given-by-the-typeof-method-mean/47546/17 "2021-05-03T03:16:01Z")
According to the documentation, the fact that `Array{T, 1}()` works is an additional method to the constructor: [Constructors · The Julia Language](https://docs.julialang.org/en/v1/manual/constructors/#man-outer-constructor-methods)
So, I agree that its use should be documented.
---
### Author:  [@jling](https://discourse.julialang.org/u/jling)
#### Post date: [May 3, 2021, 3:17am UTC](https://discourse.julialang.org/t/when-i-declare-an-empty-array-what-does-the-output-given-by-the-typeof-method-mean/47546/18 "2021-05-03T03:17:49Z")
my personal take is that an empty constructor either doesn’t work (throw an error), or does something. The “something” has a pretty natural choice here for dense Array so idk if we need to give it some special place. But then again, adding a docstring costs nothing 🤷♀️ .
btw, `T[]` is mentioned in the Array section of the docs/Manual. It’s both shorter and clearer than `Vector{T}()`