# Is it documented anywhere that I can create an array like this?

**URL:** <https://discourse.julialang.org/t/is-it-documented-anywhere-that-i-can-create-an-array-like-this/47909>\
**Category:** New to Julia\
**Created:** [October 7, 2020, 2:58am UTC](https://discourse.julialang.org/t/is-it-documented-anywhere-that-i-can-create-an-array-like-this/47909 "2020-10-07T02:58:46Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![anon60034542](https://avatars.discourse-cdn.com/v4/letter/a/90ced4/32.png) [@anon60034542](https://discourse.julialang.org/u/anon60034542)\
**Post date:** [October 7, 2020, 2:58am UTC](https://discourse.julialang.org/t/is-it-documented-anywhere-that-i-can-create-an-array-like-this/47909/1 "2020-10-07T02:58:46Z")

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I was reading about [Array initialization](https://docs.julialang.org/en/v1/base/arrays/#Core.Array-Tuple%7BUndefInitializer,Any%7D), and it talks about using the `undef` keyword for an uninitialized array. However, if you leave out the `undef` keyword and pass an iterable, you can create an array, for example:

```julia
numbers = Array{Int}([1,2,3,4,5])
5-element Array{Int32,1}:
 1
 2
 3
 4
 5

```

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**Author:** ![PetrKryslUCSD](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/petrkryslucsd/32/215825_2.png) [@PetrKryslUCSD](https://discourse.julialang.org/u/PetrKryslUCSD)\
**Post date:** [October 7, 2020, 3:12am UTC](https://discourse.julialang.org/t/is-it-documented-anywhere-that-i-can-create-an-array-like-this/47909/2 "2020-10-07T03:12:28Z")

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This is a conversion. Such as from a float array:

```julia
julia> numbers = Array{Int}(Float64[1,2,3,4,5])                                                                                                                                           
5-element Array{Int64,1}:                                                                                                                                                                 
 1                                                                                                                                                                                        
 2                                                                                                                                                                                        
 3                                                                                                                                                                                        
 4                                                                                                                                                                                        
 5     

```

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**Author:** ![tbeason](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/tbeason/32/15898_2.png) [@tbeason](https://discourse.julialang.org/u/tbeason)\
**Post date:** [October 7, 2020, 3:31am UTC](https://discourse.julialang.org/t/is-it-documented-anywhere-that-i-can-create-an-array-like-this/47909/3 "2020-10-07T03:31:44Z")

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Yea this is actually just a conversion. You are constructing the array with `[1,2,3,4,5]`

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<div class="post-metadata">

**Author:** ![anon60034542](https://avatars.discourse-cdn.com/v4/letter/a/90ced4/32.png) [@anon60034542](https://discourse.julialang.org/u/anon60034542)\
**Post date:** [October 7, 2020, 12:04pm UTC](https://discourse.julialang.org/t/is-it-documented-anywhere-that-i-can-create-an-array-like-this/47909/4 "2020-10-07T12:04:51Z")

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Is it documented anywhere that it’s a conversion? Your code obviously demonstrates it, but it seems I stumbled on conversion and thought it was initialization.

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**Author:** ![Tamas\_Papp](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/tamas_papp/32/25949_2.png) [@Tamas\_Papp](https://discourse.julialang.org/u/Tamas_Papp)\
**Post date:** [October 7, 2020, 12:25pm UTC](https://discourse.julialang.org/t/is-it-documented-anywhere-that-i-can-create-an-array-like-this/47909/5 "2020-10-07T12:25:55Z")

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Essentially it is a special case of getting a `T` from a `T(x)` method, so

[https://docs.julialang.org/en/v1/manual/conversion-and-promotion/#Conversion](https://docs.julialang.org/en/v1/manual/conversion-and-promotion/#Conversion)