I am declaring a parametric type struct A{L} end, where L should be an integer. For example, in NTuple{N,T}, the N parameter is restricted to be an integer. What is the recommended way to achieve this behavior on my custom time? I could not find the source code of NTuple.

I think that NTuple per se does not check that N is an integer, Vararg (which it is aliased to) does. For structs, the recommended solution is to check in the inner constructor, eg struct A{L} function A{L}() where L @assert L isa Integer new{L}() end end A(L::Integer) = A…

PS: the source of NTuple is in boot.jl . It is nothing more than const NTuple{N,T} = Tuple{Vararg{T,N}} There is no magic. Being able to write such core constructs in Julia lends a certain elegance to the language.

Thanks. If Vararg is also in Julia, do you know where is the source?

I think that Vararg is implemented in C.

Hi, I want to achieve the same goal except that L must limited to three integer values 1,2, 3. Is there a way to that using Union{Val{1},Val{2},Val{3}}. In fact, after create the type I want implement dispatch on these values like in the constructor of Array{T,N} Array{T,1}(::UndefInitializer, m::…

Hi, Effectively, I enter too abruptly into the discussion. Next time, I will follow the rules for discourse :smile: . In addition, my question was not clear. I mixed up two points : restrict the parameter values and enable dispatch respective to the different values of the parameter. Anyway, I foun…

Restrict type of value type parameter

General Usage

Tamas_Papp March 10, 2021, 10:21am 8

It is not clear to me what you are doing (please open a separate topic with an MWE if you need further help). In any case, validating in the constructor is still the recommended method.

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Restrict type of value type parameter

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