# What is \`Core.Box()\`?

**URL:** https://discourse.julialang.org/t/what-is-core-box/8717
**Category:** New to Julia
**Created:** [January 31, 2018, 2:31pm UTC](https://discourse.julialang.org/t/what-is-core-box/8717 "2018-01-31T14:31:44Z")
**Posts on this page:** 1
**Showing post:** 3

<div class="post-metadata">

### Author: ![yuyichao](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/yuyichao/32/20_2.png) [@yuyichao](https://discourse.julialang.org/u/yuyichao)
#### Post date: [January 31, 2018, 4:30pm UTC](https://discourse.julialang.org/t/what-is-core-box/8717/3 "2018-01-31T16:30:33Z")

</div>

No it’s totally unrelated to inference.

It’s added to the code when the frontend (parser) need a variable that can be mutated by multiple functions. (and in the case you show I’m 90% sure there was an issue for it). It does hurt inference but it is **NOT** caused by bad inference.

> [@chobbes](#):
>
> While debugging, this is something I see quite often. I didn’t find any trace in the docs and really curious about its function. Any pointer or hint is appreciated!

For the user, it’s basically the same as `Base.RefValue{Any}`. You should not use it which is why it’s not in the document.

---

_[View the full topic](https://discourse.julialang.org/t/what-is-core-box/8717)._