Proper way to include a module (Julia 1.0.1)


#1

Let’s say I have a file called test_module.jl and inside that I have defined a structure that I would like to use in other julia scripts.

module myModule
export myStruct

struct myStruct
  param1::Integer
  param2::Integer
end

end

In another file test_include.jl, I would like to access and use the myStruct structure. My intuition here (along with this SO question and Julia’s Module docs) would suggest that the below code should work. However, line 2 throws and error because the imported module has been imported as Main.myModule.

include("test_module.jl")
m = myStruct(1,2)  > UndefVarError: myStruct not defined

Making either of the next changes results in expected behavior.

Option 1:

include("test_module.jl")
m = Main.myModule.myStruct(1,2)

Option 2:

include("test_module.jl")
using Main.myModule
m = myStruct(1,2)

My Questions

  1. Am I importing the module correctly and do I have my module setup correctly? Everything that I’ve looked at suggests that I do.
  2. Why does include(julia_file) result in modules from that file being included in the Main namespace? Is there a way to change/control that?
  3. What can I change in either file so that when I include the file, I have direct access to myStruct?

#2

There should be no need to prefix by Main..

So you can do myModule.myStruct(1,2) or

julia> using .myModule

julia> myStruct
myStruct
  1. Yes, looks fine.
  2. Because you are calling the include from Main (which is the “default” module).
  3. One of the points of having a module is to namespace the symbols in there. You could just remove the module completely if you want everything to happen in the same namespace as where you include it.

#3

Thanks for the reply @kristoffer.carlsson. I tried both of your suggestions though, but neither of them worked.

Suggestion 1:

include("test_module.jl")
m = myModule.myStruct(1,2) > UndefVarError: myModule not defined

Suggestion 2:

include("test_module.jl")
using .myModule > UndefVarError: myModule not defined
m = myStruct(1,2)

Did I understand your suggestions correctly?

I tried your answer to question 3 and that worked, which is good to know. I’d still like to figure out what’s going on with module imports though.


#4
shell> cat mymod.jl
module myModule
export myStruct

struct myStruct
  param1::Integer
  param2::Integer
end

end

julia> include("mymod.jl")
Main.myModule

julia> myModule.myStruct(1,2)
Main.myModule.myStruct(1, 2)

julia> using .myModule

julia> m = myStruct(1,2)
myStruct(1, 2)

#5

Wow, really sorry about that. I’m not sure why I got those errors initially. I’ve retried your suggestions and they all work. Thanks for the help!