# If b = a, when do changes in a affect b?

**URL:** <https://discourse.julialang.org/t/if-b-a-when-do-changes-in-a-affect-b/61828>\
**Category:** New to Julia\
**Created:** [May 26, 2021, 1:46am UTC](https://discourse.julialang.org/t/if-b-a-when-do-changes-in-a-affect-b/61828 "2021-05-26T01:46:35Z")\
**Posts on this page:** 2\
**Page:** 2

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**Author:** ![lmiq](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/lmiq/32/18314_2.png) [@lmiq](https://discourse.julialang.org/u/lmiq)\
**Post date:** [May 31, 2021, 12:05pm UTC](https://discourse.julialang.org/t/if-b-a-when-do-changes-in-a-affect-b/61828/22 "2021-05-31T12:05:26Z")

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> [@paulmelis](#):
>
> `alias = vec3`

This is a case of using a non constant global variable, which should be avoided in performance critical code.

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<div class="post-metadata">

**Author:** ![paulmelis](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/paulmelis/32/35063_2.png) [@paulmelis](https://discourse.julialang.org/u/paulmelis)\
**Post date:** [May 31, 2021, 12:09pm UTC](https://discourse.julialang.org/t/if-b-a-when-do-changes-in-a-affect-b/61828/23 "2021-05-31T12:09:55Z")

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> [@lmiq](#):
>
> This is a case of using a non constant global variable, which should be avoided in performance critical code.

Right, makes sense. I guess I was expecting having a variable referencing a _type_ would not get impacted, although I didn’t really think it through.

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