I’ve come to realize that (I think) I really want the following to be possible in Julia, struct Wrapper{T<:SomeAbstractType{S}} <: OtherAbstractType{S} t::T end This doesn’t work because I have to explicitly declare the S, i.e. Wrapper{S,T<:SomeAbstractType{S}}. The sole reason I don’t want to…

[image] marius311: foo(::Wrapper{<:SomeAbstractType}) = … this exists on v0.6 Implicit type parameters, e.g. Vector{<:Real} is equivalent to Vector{T} where T<:Real, and similarly for Vector{>:Int} (#20414). See this: JuliaLang/julia/blob/master/NEWS.md Julia v1.11 Releas…

Both of those function definition exist in 0.6 already in fact, its the struct definition that does not.

I see. Tagged as development. My hunch is, it’s probably possible to take every type parameter which isn’t specified and place it in there as S <: Any. You’d have to come up with some convention for how the ordering would turn out though. But a good way to see if it would work well would be to try …

Yea, I’ve been toying with doing such a workaround by hand, basically struct Wrapper{T<:SomeAbstractType, S} <: OtherAbstractType{S} # enforce T <: SomeAbstractType{S} via inner constructor end and then (ab)use the fact that Wrapper{T} is an implicit UnionAll over S so you can omit writing the S. …

Could Julia have implicit type parameters?

Internals & Design

marius311 March 27, 2017, 10:20pm 2

Ahh should have searched a bit more, I see now there’s a pretty recent discussion with links right here Redundant type parameters

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Could Julia have implicit type parameters?

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