# Broadcast comparison of array of enum objects gives an error

**URL:** <https://discourse.julialang.org/t/broadcast-comparison-of-array-of-enum-objects-gives-an-error/68146>\
**Category:** Performance\
**Tags:** enum\
**Created:** [September 14, 2021, 12:48pm UTC](https://discourse.julialang.org/t/broadcast-comparison-of-array-of-enum-objects-gives-an-error/68146 "2021-09-14T12:48:34Z")\
**Posts on this page:** 12\
**Page:** 1

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**Author:** ![pjgorski](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/pjgorski/32/4802_2.png) [@pjgorski](https://discourse.julialang.org/u/pjgorski)\
**Post date:** [September 14, 2021, 12:48pm UTC](https://discourse.julialang.org/t/broadcast-comparison-of-array-of-enum-objects-gives-an-error/68146/1 "2021-09-14T12:48:34Z")

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I have an array of `@Enum` objects. I want to count the array elements having a certain value.

```julia
@enum E x = 0 y = 1
Es = [E(0) for i in 1:100]
sum(Es .== E(0))

```

Above code and just `Es .== E(0)` gives the following error:

> ERROR: MethodError: no method matching length(::E)  
> Closest candidates are:  
> length(::Core.SimpleVector) at essentials.jl:582  
> length(::Base.MethodList) at reflection.jl:732  
> length(::Core.MethodTable) at reflection.jl:806

I know that I can count elements using for instance  
`sum([e == E(0) for e in Es])`  
but I wonder what’s wrong in the 1st approach.

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**Author:** ![sijo](https://avatars.discourse-cdn.com/v4/letter/s/da6949/32.png) [@sijo](https://discourse.julialang.org/u/sijo)\
**Post date:** [September 14, 2021, 12:52pm UTC](https://discourse.julialang.org/t/broadcast-comparison-of-array-of-enum-objects-gives-an-error/68146/2 "2021-09-14T12:52:50Z")

</div>

Which version of Julia are you using? Your code works for me on 1.6.1 and 1.7.

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<div class="post-metadata">

**Author:** ![pjgorski](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/pjgorski/32/4802_2.png) [@pjgorski](https://discourse.julialang.org/u/pjgorski)\
**Post date:** [September 14, 2021, 12:59pm UTC](https://discourse.julialang.org/t/broadcast-comparison-of-array-of-enum-objects-gives-an-error/68146/3 "2021-09-14T12:59:52Z")

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Thanks for the quick reply.  
I am using LTS version.

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<div class="post-metadata">

**Author:** ![sijo](https://avatars.discourse-cdn.com/v4/letter/s/da6949/32.png) [@sijo](https://discourse.julialang.org/u/sijo)\
**Post date:** [September 14, 2021, 1:59pm UTC](https://discourse.julialang.org/t/broadcast-comparison-of-array-of-enum-objects-gives-an-error/68146/4 "2021-09-14T13:59:41Z")

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I think you’re getting hit by [https://github.com/JuliaLang/julia/issues/30669](https://github.com/JuliaLang/julia/issues/30669) . It looks like the bug fix wasn’t backported to Julia 1.0.

Do you need to stay on LTS? Note that the LTS is not the “recommended version”, it’s really just for people who basically cannot upgrade.

(I’m still a bit surprised that such bugfixes don’t get backported.)

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<div class="post-metadata">

**Author:** ![pjgorski](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/pjgorski/32/4802_2.png) [@pjgorski](https://discourse.julialang.org/u/pjgorski)\
**Post date:** [September 15, 2021, 8:34am UTC](https://discourse.julialang.org/t/broadcast-comparison-of-array-of-enum-objects-gives-an-error/68146/5 "2021-09-15T08:34:09Z")

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It surprises me that LTS is not recommended version, because it stands for Long Term.  
I always stick to LTS versions, because I want to use (and re-use) code that is best, was tested and has the least number of errors (that would be my idea of LTS).  
Why do I do that? For instance, I have some old code from some publication, I might want to open it for 5 min half a year after the publication and if I upgraded the programming language version, I might need two days to make it work again.

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<div class="post-metadata">

**Author:** ![sijo](https://avatars.discourse-cdn.com/v4/letter/s/da6949/32.png) [@sijo](https://discourse.julialang.org/u/sijo)\
**Post date:** [September 15, 2021, 10:07am UTC](https://discourse.julialang.org/t/broadcast-comparison-of-array-of-enum-objects-gives-an-error/68146/6 "2021-09-15T10:07:04Z")

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That makes sense (I have a similar approach for my OS software) but for Julia it’s not a good idea: the LTS is definitely not the best code, probably not even the most tested since the majority of user upgrade quickly to new versions I think.

I agree it’s confusing because you would expect an LTS to get all the bugfixes, and it’s not the case for some reason. But even if it did get all the fixes, you should use a more recent version: with LTS you’re stuck with old, inferior versions of third-party packages because the developers wanted to use important features introduced in Julia 1.3 for example.

Here’s a recent take from a core developer:

> [@What are the current plans regarding a new LTS Julia version?](https://discourse.julialang.org/t/what-are-the-current-plans-regarding-a-new-lts-julia-version/63501/24):
>
> The plan is still for 1.6 to be the new LTS. There are always features in new releases that someone would like to have in an LTS version. Aside from the manifest format, which is being backported to 1.6, none of these seem like show-stoppers. The vast majority of people should be using whatever the latest Julia version is, not staying on the LTS. There seems to be some misunderstanding that the LTS is better to run for some reason, which is very much not the case. You should only be using the L…

In summary, the language and ecosystem are moving too fast right now for LTS to be the best environment.

Fortunately, Julia has you covered when it comes to running old code 🙂 It’s easy to install the old Julia version that was used for an old project (just a zip file to uncompress somewhere). And assuming you have made a Julia project for your publication (and you really should have) then you have a `Project.toml` and `Manifest.toml` that describe the versions of packages used in that project. Years later you can get the correct package versions by running `]instantiate`. And starting with Julia 1.7, the Julia version itself will be recorded in the manifest.

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<div class="post-metadata">

**Author:** ![nilshg](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/nilshg/32/2283_2.png) [@nilshg](https://discourse.julialang.org/u/nilshg)\
**Post date:** [September 15, 2021, 10:33am UTC](https://discourse.julialang.org/t/broadcast-comparison-of-array-of-enum-objects-gives-an-error/68146/7 "2021-09-15T10:33:05Z")

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See also [Julia’s Release Process](https://julialang.org/blog/2019/08/release-process/#risk_tolerance_personas) for a discussion about the roles of LTS and other Julia versions and the “risk personas” these are targeted at.

P.S. if you do end up upgrading to 1.7 (which is the current release candidate) or 1.6 (current stable release) I do envy you - Julia has gotten so much better over those 6/7 point releases, with a lot of effort going into making the overall usability experience smoother, that it will by quite the (positive) shock.

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<div class="post-metadata">

**Author:** ![stevengj](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/stevengj/32/71_2.png) [@stevengj](https://discourse.julialang.org/u/stevengj)\
**Post date:** [September 15, 2021, 11:55am UTC](https://discourse.julialang.org/t/broadcast-comparison-of-array-of-enum-objects-gives-an-error/68146/8 "2021-09-15T11:55:11Z")

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> [@sijo](#):
>
> (I’m still a bit surprised that such bugfixes don’t get backported.)

That’s because it’s not a bugfix. It’s technically a new feature (that you don’t have to type `Ref` when broadcasting enums.)

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<div class="post-metadata">

**Author:** ![oxinabox](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/oxinabox/32/206603_2.png) [@oxinabox](https://discourse.julialang.org/u/oxinabox)\
**Post date:** [September 15, 2021, 12:28pm UTC](https://discourse.julialang.org/t/broadcast-comparison-of-array-of-enum-objects-gives-an-error/68146/9 "2021-09-15T12:28:03Z")

</div>

> [@sijo](#):
>
> Do you need to stay on LTS? Note that the LTS is not the “recommended version”, it’s really just for people who basically cannot upgrade.

> [@pjgorski](#):
>
> It surprises me that LTS is not recommended version, because it stands for Long Term.

To clarify: the LTS is not the “recommended version” because there is no such thing as a official “recommended version”.  
There are at any point in time 3-4 supported versions:  
LTS, Stable, Nightly and sometimes (including right now) the beta/release-candidate  
All those versions, and even versions that are not currently supported can recommended for some use cases some of the time.

No-one ( not @sijo, not me, not a core developer) can tell you a general recommended version, without a lot more details that you should probably make a separate thread to provide.

> [@sijo](#):
>
> In summary, the language and ecosystem are moving too fast right now for LTS to be the best environment.

Generally it is true that the newer releases with newer features are better for most (but not all people.)  
Because Julia wouldn’t be going around adding features that make the language worse, that would make no sense.

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<div class="post-metadata">

**Author:** ![pjgorski](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/pjgorski/32/4802_2.png) [@pjgorski](https://discourse.julialang.org/u/pjgorski)\
**Post date:** [September 15, 2021, 12:43pm UTC](https://discourse.julialang.org/t/broadcast-comparison-of-array-of-enum-objects-gives-an-error/68146/10 "2021-09-15T12:43:03Z")

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How to use `Ref` when broadcasting enums (like in the example in the 1st post)?

P.S. Thanks to all for general comments. I feel tempted to upgrade 😛 and I supposed I will do it when starting new project.

---

<div class="post-metadata">

**Author:** ![oxinabox](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/oxinabox/32/206603_2.png) [@oxinabox](https://discourse.julialang.org/u/oxinabox)\
**Post date:** [September 15, 2021, 12:47pm UTC](https://discourse.julialang.org/t/broadcast-comparison-of-array-of-enum-objects-gives-an-error/68146/11 "2021-09-15T12:47:53Z")

</div>

> [@pjgorski](#):
>
> How to use `Ref` when broadcasting enums (like in the example in the 1st post)?

```julia
@enum E x = 0 y = 1
Es = [E(0) for i in 1:100]
sum(Es .== Ref(E(0)))

```

A case can also be made that rather than using `Ref` wrapping it in tuple, which also works:|

```julia
julia> sum(Es .== Ref(E(0)))
100

julia> sum(Es .== (E(0),))
100

```

---

<div class="post-metadata">

**Author:** ![sijo](https://avatars.discourse-cdn.com/v4/letter/s/da6949/32.png) [@sijo](https://discourse.julialang.org/u/sijo)\
**Post date:** [September 15, 2021, 1:56pm UTC](https://discourse.julialang.org/t/broadcast-comparison-of-array-of-enum-objects-gives-an-error/68146/12 "2021-09-15T13:56:24Z")

</div>

> [@oxinabox](#):
>
> No-one ( not @sudete, not me, not a core developer) can tell you a general recommended version, without a lot more details that you should probably make a separate thread to provide.

This previously mentioned quote from @StefanKarpinski reads like a recommendation to me:

> The vast majority of people should be using whatever the latest Julia version is […] You should _only_ be using the LTS if it’s very expensive or risky for you to go through the process of upgrading, which is not the case for 99% of users.

(I think people understand “recommended” as meaning “for most use cases”.)

> [@oxinabox](#):
>
> Generally it is true that the newer releases with newer features are better for most (but n people. Because Julia wouldn’t be going around adding features that make the language worse, that would make no sense.

I don’t think that’s generally true (that new features outweigh the benefits of stability), but that it’s currently true for Julia in typical use cases.

Let’s not shy away from recommendations. I think those from @StefanKarpinski are useful for new users. On the other hand, “there are all these versions and a lot of details about your use case are required to determine the appropriate one” sounds intimidating/overwhelming and makes the choice seem more difficult than it is.