Nested parametric type?

New to Julia
1

I’m working on a tree code where I have defined the following types:

using StaticArrays

mutable struct Data{N,T}
	pos::SVector{N,T}
	mass::T
end

mutable struct Node{N,T}
    center::SVector{N,T}
	p::Union{Data{N,T}, Nothing}
	child::Union{Array{Node{N,T},1}, Nothing}
end

and I now want to change the definition of Node into

mutable struct Node{Data{N,T}}
    center::SVector{N,T}
	p::Union{Data{N,T}, Nothing}
	child::Union{Array{Node{N,T},1}, Nothing}
end

which gives me an error: ERROR: LoadError: syntax: invalid variable expression in "where" around. Is it possible to have a nested parametric type?

The reason I’m doing this is because I want to let the type Data to be flexible/extendable and eventually I want to replace it with AbstractData{N,T} such that I can add more data members when I need. For example,

mutable struct Data2{N,T} <: AbstractData{N,T}
	pos::SVector{N,T}
	mass::T
	charge::T
end

and I want Node to be aware of what kind of AbstractData it carries.

2 
mutable struct Node{N, T, D<:Data{N,T}}
    center::SVector{N,T}
    p::Union{D, Nothing}
    child::Union{Array{Node{N,T},1}, Nothing}
end

might be what you want.

2 Likes
3

Yes, It works! Awesome!!!