Module Inheritance Doubts

General Usage
1

I’m doing a framework for recommendation systems called Persa.jl (https://github.com/filipebraida/Persa.jl). My idea is that the core is a module and it’s possible to extend this framework to solve a Collaborative Filtering problem (such as cold start, noise, etc) and also be able to create/implement new prediction models.

Currently, I’ve created a wrapper for the suprise-python framework and use their models.

I would like to remove from Persa.jl project and create a separate project.

Here’s an example:

Surprise
type GlobalMean2 <: Persa.CFModel
  μ::Float64
end

GlobalMean2{T<:Persa.CFDatasetAbstract}(dataset::T) = GlobalMean2(Persa.mean(dataset))

function Persa.train!{T<:Persa.CFDatasetAbstract}(model::Surprise.GlobalMean2, dataset::T)

end

Persa.predict(model::Surprise.GlobalMean2, user::Int, item::Int) = model.μ

Persa.canPredict(model::Surprise.GlobalMean2, user::Int, item::Int) = true
end

When I call it, Julia gives an error saying that it cannot convert the input parameter (Surprise.GlobalMean2 (ds_train)).

In fact, what I would like to do would be module inheritance.

Thanks!

2

That’s usually done by writing the interface on abstract types, and allowing other modules to create their own concrete instances and overload specific methods as necessary. It’s not clear to me what exactly you’re trying to do.

3

Thanks Chris.

I will detail more my problem.

I would like to create a wrapper that use framework Persa.jl. So, I create a type and a function to wrapper a function of the python-surprise package.

Code:

type SurpriseKNNBaseline <: SurpriseModel
  object::PyObject
  preferences::Persa.RatingPreferences
  k::Int
  min_k::Int
end

function SurpriseKNNBaseline(dataset::Persa.CFDatasetAbstract; k = 40, min_k = 1)
  return SurpriseKNNBaseline(surprise.KNNBaseline(k = k, min_k = min_k), dataset.preferences, k , min_k);
end

This construction gives me this error:

MethodError: Cannot `convert` an object of type Persa.RatingPreferences{Float64} to an object of type Persa.RatingPreferences{Float64}
This may have arisen from a call to the constructor Persa.RatingPreferences{Float64}(...),
since type constructors fall back to convert methods.
 in #SurpriseKNNWithMeans#3(::Int64, ::Int64, ::Type{T}, ::Persa.CFDataset) at methods.jl:40
 in (::Core.#kw#Type)(::Array{Any,1}, ::Type{Surprise.SurpriseKNNWithMeans}, ::Persa.CFDataset) at <missing>:0
 in include_string(::String, ::String) at loading.jl:441
 in eval(::Module, ::Any) at boot.jl:234
 in (::Atom.##65#68)() at eval.jl:102
 in withpath(::Atom.##65#68, ::Void) at utils.jl:30
 in withpath(::Function, ::Void) at eval.jl:38
 in macro expansion at eval.jl:101 [inlined]
 in (::Atom.##64#67{Dict{String,Any}})() at task.jl:60

I tried to change some things but nothing worked.

Thanks you for your help.

4 
type SurpriseKNNBaseline{PT<:PyObject,T} <: SurpriseModel
  object::PT
  preferences::Persa.RatingPreferences{T}
  k::Int
  min_k::Int
end

?