# From baremodule to Dict

**URL:** <https://discourse.julialang.org/t/from-baremodule-to-dict/10744>\
**Category:** General Usage\
**Created:** [May 6, 2018, 7:35pm UTC](https://discourse.julialang.org/t/from-baremodule-to-dict/10744 "2018-05-06T19:35:09Z")\
**Posts on this page:** 10\
**Page:** 1

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**Author:** ![scelles](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/scelles/32/220408_2.png) [@scelles](https://discourse.julialang.org/u/scelles)\
**Post date:** [May 6, 2018, 7:35pm UTC](https://discourse.julialang.org/t/from-baremodule-to-dict/10744/1 "2018-05-06T19:35:09Z")

</div>

Hello,

I defined a baremodule

> baremodule Return  
> const INVALID\_CMD = 0x00  
> const CMD\_FINISHED = 0x01  
> end

I would like to get a Dict from this module with keys being 0x00 and 0x01 (and more …)

How can I achieve this task?

Kind regards

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**Author:** ![rdeits](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/rdeits/32/286_2.png) [@rdeits](https://discourse.julialang.org/u/rdeits)\
**Post date:** [May 6, 2018, 7:44pm UTC](https://discourse.julialang.org/t/from-baremodule-to-dict/10744/2 "2018-05-06T19:44:24Z")

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You can do this with `names` and `getfield`, but using a module in this way is very uncommon and probably not a good idea. What are you trying to do, and why do you need a module to store these constants?

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**Author:** ![jonathanBieler](https://avatars.discourse-cdn.com/v4/letter/j/82dd89/32.png) [@jonathanBieler](https://discourse.julialang.org/u/jonathanBieler)\
**Post date:** [May 6, 2018, 8:16pm UTC](https://discourse.julialang.org/t/from-baremodule-to-dict/10744/3 "2018-05-06T20:16:46Z")

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I sometimes overload `enumerate` to list all the constants in a baremodule:

```julia
import Base.enumerate
function enumerate(::Type{T}, mod) where T
    n = names(mod,true)
    v = map(x->getfield(mod,x),n)
    filter(v->typeof(v)==T,v)
end

julia> enumerate(UInt8,Return)
2-element Array{Any,1}:
0x01
0x00

```

But you could use an enum too.

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<div class="post-metadata">

**Author:** ![scelles](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/scelles/32/220408_2.png) [@scelles](https://discourse.julialang.org/u/scelles)\
**Post date:** [May 7, 2018, 7:48pm UTC](https://discourse.julialang.org/t/from-baremodule-to-dict/10744/4 "2018-05-07T19:48:00Z")

</div>

I noticed this kind of usage in

[https://github.com/zyedidia/SFML.jl/blob/f7ce40b3289864f6df515605e46e07cd9aba3f0e/src/julia/Window/keyboard.jl#L5](https://github.com/zyedidia/SFML.jl/blob/f7ce40b3289864f6df515605e46e07cd9aba3f0e/src/julia/Window/keyboard.jl#L5)

What I like is that I need to do `Return.CMD_FINISHED` to access 0x01 constant

With Enum,

```
julia> @enum ReturnE::UInt8 INVALID_CMD = 0x00 CMD_FINISHED = 0x01
julia> ReturnE
Enum ReturnE:
INVALID_CMD = 0
CMD_FINISHED = 1

```

One problem, is that despite I defined type of `UInt8`, Enum doesn’t seem to keep a track of it (see 0, 1, instead of 0x00 and 0x01).

Moreover I can access directly to `INVALID_CMD` without preceding with `ReturnE`  
which is not something I like

With Enum, accessing to a given key with a value can be done using `ReturnE[0x01][1]` and I get `CMD_FINISHED::ReturnE = 1`

What I don’t like with enumerate approach is that we get an Array of Any.

I just need to be able to get `:CMD_FINISHED` from `0x01`

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<div class="post-metadata">

**Author:** ![rdeits](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/rdeits/32/286_2.png) [@rdeits](https://discourse.julialang.org/u/rdeits)\
**Post date:** [May 7, 2018, 8:00pm UTC](https://discourse.julialang.org/t/from-baremodule-to-dict/10744/5 "2018-05-07T20:00:47Z")

</div>

Ah, I see. Your `UInt8` declaration in the `@enum` is working, it’s just that Julia is _displaying_ the value by converting it to a plain `Int`. I’m honestly not sure why that’s done, but it’s possible to prove that your enum values really are UInt8s:

```julia
julia> @enum ReturnE::UInt8 INVALID_CMD = 0x00 CMD_FINISHED = 0x01

julia> sizeof(CMD_FINISHED)
1

julia> Base.Enums.basetype(typeof(CMD_FINISHED))
UInt8

```

`sizeof` gives the size in bytes, so `CMD_FINISHED` is stored in exactly 1 byte.

It’s perfectly reasonable to want a namespace for your enum. How about the following:

```julia
julia> module Return

       export ReturnCodes
       @enum ReturnCodes::UInt8 INVALID_CMD=0x00 CMD_FINISHED=0x01

       end
Return

julia> sizeof(Return.CMD_FINISHED)
1

julia> Return.ReturnCodes[0x01]
1-element Array{Return.ReturnCodes,1}:
 CMD_FINISHED

```

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<div class="post-metadata">

**Author:** ![scelles](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/scelles/32/220408_2.png) [@scelles](https://discourse.julialang.org/u/scelles)\
**Post date:** [May 7, 2018, 8:11pm UTC](https://discourse.julialang.org/t/from-baremodule-to-dict/10744/6 "2018-05-07T20:11:22Z")

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Thanks a lot @rdeits!

Maybe we should open an issue about Enum display with UInt8?

I also wonder how to get `CMD_FINISHED` value as UInt8 without specifying type.

Is `Base.Enums.basetype(Return.ReturnCodes)(Return.CMD_FINISHED)` the simplest approach?

===

About baremodule approach, thanks to @jonathanBieler suggestion I implemented 2 functions

```julia
function getSymbols(mod::Module, value)
  vct = Vector{Symbol}()
  for n in names(mod, true)
    if n != Symbol(mod)
      v = getfield(mod, n)
      if v == value
        push!(vct, n)
      end
    end
  end
  vct
end

function getDict(mod::Module, t::Type)
  d = Dict{Symbol,t}()
  for n in names(mod, true)
    if n != Symbol(mod)
      v = getfield(mod, n)
      if !haskey(d, n)
        d[n] = v
      else
        error("$n is not unique - $(d[n]) $v")
      end
    end
  end
  d
end

```

I posted it here but I think I will in fact use the Enum approach (bracketed version) as it also insure that values are unique at creation.

```julia
module Return
  @enum(ReturnCodes::UInt8,
    CMD_FINISHED = 0x01,
    INVALID_CMD = 0x00,
  )

  function code(val)
    Symbol(Return.ReturnCodes[val][1])
  end

end

```

PS: edit 2018-06-06 Julia 0.7 now supports begin/end for enum  
[https://github.com/JuliaLang/julia/blame/master/NEWS.md#L44](https://github.com/JuliaLang/julia/blame/master/NEWS.md#L44)  
[https://github.com/JuliaLang/julia/pull/25424](https://github.com/JuliaLang/julia/pull/25424)

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<div class="post-metadata">

**Author:** ![scelles](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/scelles/32/220408_2.png) [@scelles](https://discourse.julialang.org/u/scelles)\
**Post date:** [May 7, 2018, 8:55pm UTC](https://discourse.julialang.org/t/from-baremodule-to-dict/10744/7 "2018-05-07T20:55:27Z")

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Issue opened at [https://github.com/JuliaLang/julia/issues/27025](https://github.com/JuliaLang/julia/issues/27025) about display of Enum with UInt8

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<div class="post-metadata">

**Author:** ![mauro3](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/mauro3/32/292_2.png) [@mauro3](https://discourse.julialang.org/u/mauro3)\
**Post date:** [May 7, 2018, 9:21pm UTC](https://discourse.julialang.org/t/from-baremodule-to-dict/10744/8 "2018-05-07T21:21:11Z")

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I’ve also found at times that name-spaced enumerations would be nice. Mainly because otherwise the items seem a bit polluting on the name-space and also are a hassle to export (or rather not). I like @rdeits’s solution (but is the `export` needed?).

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<div class="post-metadata">

**Author:** ![rdeits](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/rdeits/32/286_2.png) [@rdeits](https://discourse.julialang.org/u/rdeits)\
**Post date:** [May 7, 2018, 9:33pm UTC](https://discourse.julialang.org/t/from-baremodule-to-dict/10744/9 "2018-05-07T21:33:52Z")

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Nope, `export` isn’t necessary. I just thought it might be convenient.

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<div class="post-metadata">

**Author:** ![scelles](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/scelles/32/220408_2.png) [@scelles](https://discourse.julialang.org/u/scelles)\
**Post date:** [October 5, 2018, 12:36pm UTC](https://discourse.julialang.org/t/from-baremodule-to-dict/10744/10 "2018-10-05T12:36:50Z")

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SuperEnum

[https://github.com/kindlychung/SuperEnum.jl](https://github.com/kindlychung/SuperEnum.jl)

provides a macro to define automatically enum inside module.