Type definition works in the REPL, doesn't work in a module

General Usage
1

I feel like I’m missing something basic here. The following code works when pasted in to the REPL:

using DataStructures: MutableLinkedList

module MyModule

   struct MapEntry{T<:Number, M, N}
      IC::Array{T,M}
      FC::Array{T,M}
      Vec::Array{T,N}
   end

   AssocMap = MutableLinkedList{MapEntry}
 end

I can then create variables of type AssocMap, which work as I expect. But when I put that same code in a module definition and include() the module file, I get the following error:

ERROR: LoadError: UndefVarError: MutableLinkedList not defined

pointing to that last line. Which means that the assoc = MutableLinkedList line is interpreted as a type definition when executed in the REPL, but as a variable instantiation when in a file?

2

The only thing that makes sense to me is that you did not import MutableLinkedList in the context of that module.

3

I did though. I’ll mod the OP.

4

Modules do not inherit variables from their parent scopes. This isn’t really about type definitions at all, but simply the fact that you cannot do:

julia> x = 1
1

julia> module Foo
         @show x
       end
ERROR: UndefVarError: x not defined
Stacktrace:
 [1] top-level scope at show.jl:641

Instead, you need to use using to bring any names from an outer module into the inner one:

julia> module Outer
         x = 1
         
         module Inner
           using ..Outer: x
           @show x
         end
       end
x = 1
4 Likes
5

Yep, that’s it. Thanks!

6

I should have been clearer. What @rdeits carefully explained was what I intended to mean.