# Very best way to concatenate an array of arrays

**URL:** <https://discourse.julialang.org/t/very-best-way-to-concatenate-an-array-of-arrays/8672>\
**Category:** General Usage\
**Tags:** arrays\
**Created:** [January 29, 2018, 3:29pm UTC](https://discourse.julialang.org/t/very-best-way-to-concatenate-an-array-of-arrays/8672 "2018-01-29T15:29:50Z")\
**Posts on this page:** 1\
**Showing post:** 32

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**Author:** ![DavidKMaslen](https://avatars.discourse-cdn.com/v4/letter/d/b5e925/32.png) [@DavidKMaslen](https://discourse.julialang.org/u/DavidKMaslen)\
**Post date:** [October 12, 2019, 6:31pm UTC](https://discourse.julialang.org/t/very-best-way-to-concatenate-an-array-of-arrays/8672/32 "2019-10-12T18:31:38Z")

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Thanks. I also just used @benchmark to see how many allocations were being made and observed just 1.

Where would the documentation of this feature go? It’s a feature of reduce, but someone looking for advice on how to properly flatten a vector of vectors would be unlikely to look there.

On a completely personal note - I personally find myself not wanting to use reduce because the documentation explicitly states there are no guarantees either now, or in the future, on what it does.

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