# \`typ\` field in Expr objects

**URL:** <https://discourse.julialang.org/t/typ-field-in-expr-objects/626>\
**Category:** General Usage\
**Tags:** question\
**Created:** [November 29, 2016, 9:11am UTC](https://discourse.julialang.org/t/typ-field-in-expr-objects/626 "2016-11-29T09:11:55Z")\
**Posts on this page:** 4\
**Page:** 1

<div class="post-metadata">

**Author:** ![ZacLN](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/zacln/32/2748_2.png) [@ZacLN](https://discourse.julialang.org/u/ZacLN)\
**Post date:** [November 29, 2016, 9:11am UTC](https://discourse.julialang.org/t/typ-field-in-expr-objects/626/1 "2016-11-29T09:11:55Z")

</div>

What is the purpose/use of the `typ` field of an `Expr`. I’m using it with JuliaParser to store locations of expressions as they’re parsed (not for evaluation) but was wondering what the side effects of doing so is\>

---

<div class="post-metadata">

**Author:** ![StefanKarpinski](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/stefankarpinski/32/24_2.png) [@StefanKarpinski](https://discourse.julialang.org/u/StefanKarpinski)\
**Post date:** [November 29, 2016, 4:46pm UTC](https://discourse.julialang.org/t/typ-field-in-expr-objects/626/2 "2016-11-29T16:46:10Z")

</div>

It’s used by type inference to record the computed type bounds on expressions. If you’re not going to pass an expression to type inference (e.g. via eval), then it should be safe to use it for something else.

---

<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:** [November 29, 2016, 4:57pm UTC](https://discourse.julialang.org/t/typ-field-in-expr-objects/626/3 "2016-11-29T16:57:10Z")

</div>

I’m almost sure `eval` and type inference ignores it as input. Do note that the field can be gone at anytime without warning.

---

<div class="post-metadata">

**Author:** ![ZacLN](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/zacln/32/2748_2.png) [@ZacLN](https://discourse.julialang.org/u/ZacLN)\
**Post date:** [November 29, 2016, 5:27pm UTC](https://discourse.julialang.org/t/typ-field-in-expr-objects/626/4 "2016-11-29T17:27:33Z")

</div>

Thanks, that’s good to hear!