Method error with multiple definition of the same submodule - julia

Question

Imagine that I have the following module in a file myMod.jl:
module myMod
type T
i::Int
end
function sum(T1::T, T2::T)
T1.i + T2.i
end
end
Now, I want to define two modules elsewhere that are able to use the type T defined in myMod, so let me write the following code:
# --- Define first module
module A
include("myMod.jl")
type Ta
a::myMod.T
end
end
# --- Define second module
module B
include("myMod.jl")
type Tb
a::myMod.T
end
end
# --- Use the modules
using A, B
v1 = A.Ta(A.myMod.T(1))
v2 = B.Tb(B.myMod.T(2))
So far so good, everything works fine. I can even call the sum method with
A.myMod.sum(v1.a, v1.a) # Returns 2, as expected
However, I can't sum v1.a and v2.a, despite typeof(v1.a) and typeof(v2.a) are both T:
A.myMod.sum(v1.a, v2.a)
Error evaluating .../myTest.jl: sum has no method matching sum(::T,
::T)
I have the feeling that though v2.a is of type T, Julia remembers that is has been created inside module B and thus doesn't recognize it as a T object.
Is there a workaround ? Or a more elegant/julianistic way of making the sum function work with both v1.a and v2.a ?

Answer 1

The include function is basically the same as just pasting the code from myMod.jl into the location where include was called. The way you're using it, it's as though you were defining two different modules, A.myMod and B.myMod, which happen to have the exact same implementation. Although the two modules have identical implementations, they do not share the same identity. Therefore A.myMod.T is not the same type as B.myMod.T.
What you want to do is define the myMod module just once, then use it when defining Ta and Tb. You can do so using using as shown below. I've assumed that myMod is still defined in the file myMod.jl, but you could just define them all in the same file if you wanted to.
include("myMod.jl")
# --- Define first module
module A
using myMod
type Ta
a::myMod.T
end
end
# --- Define second module
module B
using myMod
type Tb
a::myMod.T
end
end
# --- Use the modules
using A, B, myMod
v1 = A.Ta(myMod.T(1))
v2 = B.Tb(myMod.T(2))
myMod.sum(v1.a, v2.a)