hello, coming across StatsBase.AbstractWeights, I found it could enforce fields to be inherited. e.g. import StatsBase struct MyWeights1{S<:Real, T<:Real, V<:AbstractVector{T}} <: StatsBase.AbstractWeights{S, T, V} values::V sum::S end struct MyWeights2{S<:Real, T<:Real, V<:AbstractVector…

I don’t know the code but I assume that it just requires those fields to be defined for the methods to work. Have a look at show method which threw above error: @less show(stdout, MyWeights2([1.0, 2.0], 3.0)). I suspect it is defined on the AbstractWeights and accesses .value.

oic! it does not enforce the field to inherit at all! The following call: y = MyWeights2([1.0, 2.0], 3.0) would make the REPL to show() the object, which in turn calls: Base.size(wv::AbstractWeights) = size(wv.values) that triggers an error. Instead, if we suppress REPL from show()ing the objec…

Yes, that works. But presumably other functionality of StatsBase doesn’t work either with those fields. It should be described in the docs, what needs to be satisfied to hook into the functionality of StatsBase.

actuall, it’s disappointing: seems like there’s no easy way to enforce the fields to be inherited. any suggestions?

Yep. Interfaces in Julia are informal. There are some packages which help with inheriting fields, there was an announcement recently on discourse.

[image] mauro3: , there was an announcement recently on discourse. could you please give a link?

[image] GitHub - gcalderone/ReusePatterns.jl: Implement composition and concrete... Implement composition and concrete subtyping in Julia. - GitHub - gcalderone/ReusePatterns.jl: Implement composition and concrete subtyping in Julia. [image] W…

[image] tomtom: could someone be nice enough to explain the trick? thanks. There is no trick. As @mauro3 explained, some code just assumes that when typeof(x) <: AbstractWeights, it has certain fields implemented. It is not clear that StatsBase.AbstractWeights was meant to be extended outsid…

How to enforce the fields to be inherited?

New to Julia

mauro3 February 12, 2019, 10:39am 8

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How to enforce the fields to be inherited?

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