Subtyping with Parametric Abstract Types

General Usage
1

I don’t understand why

struct MultiDist{D <: UnivariateDistribution{S <: ValueSupport}} <: MultivariateDistribution{S <: ValueSupport}
    dist::D
    n::Int
end

returns that S in undefined. I also tried

struct MultiDist{D <: UnivariateDistribution{S}} <: MultivariateDistribution{S} where S <: ValueSupport
    dist::D
    n::Int
end
2

isn’t …

julia> Sampleable{Univariate,Discrete} <: Sampleable{Multivariate,Discrete}
false

julia> Sampleable{Univariate,Continuous} <: Sampleable{Multivariate,Continuous}
false

julia> Distribution{Univariate,Discrete} <: Distribution{Multivariate,Discrete}
false

julia> Distribution{Univariate,Continuous} <: Distribution{Multivariate,Continuous}
false

what are you trying to achieve?

3

MultiDist is a struct that is a MultivariateDistribution. One of the fields of that struct, dist, is a UnivariateDistribution. Both should have the same ValueSupport, either Continuous or Discrete. At no point in my example do I imply one of the
relations you wrote.

4

sorry, then I misunderstood you.

5

Because you need to define S as a type parameter in order to use it, i.e. MultiIDist{S <: ValueSupport, ...}. Except in special cases like declaration of type parameter and declaration of type, <: doesn’t automatically declare a type parameter, the S <: ValueSupport in your code is simply an expression and the value of that expression is being applied to the type.

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