# Conditional indexing issue with float precision

**URL:** <https://discourse.julialang.org/t/conditional-indexing-issue-with-float-precision/27833>\
**Category:** General Usage\
**Created:** [August 22, 2019, 6:10am UTC](https://discourse.julialang.org/t/conditional-indexing-issue-with-float-precision/27833 "2019-08-22T06:10:27Z")\
**Posts on this page:** 1\
**Showing post:** 2

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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:** [August 22, 2019, 7:04am UTC](https://discourse.julialang.org/t/conditional-indexing-issue-with-float-precision/27833/2 "2019-08-22T07:04:43Z")

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This is to be expected because of floating point error:

> [@PSA: floating-point arithmetic](https://discourse.julialang.org/t/psa-floating-point-arithmetic/8678):
>
> Sometimes people are surprised by the results of floating-point calculations such as julia\> 5/6 0.8333333333333334 # shouldn't the last digit be 3? julia\> 2.6 - 0.7 - 1.9 2.220446049250313e-16 # shouldn't the answer be 0? These are not bugs in Julia. They’re consequences of the IEEE-standard 64-bit binary representation of floating-point numbers that is burned into computer hardware, which Julia and many other languages use by default. Brief explanation You can t…

If there is an outcome for a calculation that follows from theory, you should generate that directly.

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