Continuing the discussion from Unitful dispatch : I want to dispatch specifically on u"inch". What am I missing? In this MWE, I want mm(1), mm(1u"inch"), and mm(1.0u"inch") to all return 25.4 mm. using Unitful InchType = Quantity{ <:Any, Unitful.𝐋, Unitful.FreeUnits{(Unitful.inch,), Un…

I found this confusing but it turns out to be due to how Unitful.jl prints units and what you really want is the type of a unit, demonstrated below: julia> InchType = Quantity{ <:Any, Unitful.𝐋, typeof(Unitful.inch), } Quantity{<:Any, 𝐋, Unitful.FreeUnits{(in…

I’ve had this desire in the past but can’t find my resolution; since then I wrote UnitTypes to help with this sort of thing. The package works by providing macros that allow defining of new unit types and conversions between them. A parallel package, ExchangeUnitful, can provide converts to/from U…

One possible solution: using Unitful # type to dispatch on length quantities const Length{T} = Quantity{T,u"𝐋"} # requested behavior mm(x::Number) = mm(x * u"inch") mm(x::Length) = float(uconvert(u"mm", x)) mm(x::Quantity) = throw(ArgumentError("invalid units")) # examples of usage mm(1) # 25.4 …

I’m mostly just confused why julia> x = 1u"inch" 1 inch julia> XType = typeof(x) Quantity{Int64, 𝐋, Unitful.FreeUnits{(inch,), 𝐋, nothing}} julia> LengthType = Quantity{<:Any, Unitful.𝐋} Quantity{<:Any, 𝐋} julia> XType <: LengthType true but julia> InchType = Quantity{ <:Any, …

[image] Nathan_Boyer: when I’ve copied everything else exactly. Julia’s type parameters are invariant: Types · The Julia Language Documentation for The Julia Language. Another example: julia> abstract type A{T₁,T₂,T₃} end julia> A{Int,Int,Int} <: A…

However, if you want to dispatch on the unit, it could also be more readable to treat the unit like a trait: f(x::Number) = _f(unit(x), x) _f(::Unitful.Units, x) = nothing _f(::typeof(Unitful.inch), x) = something

Saving this here for myself: [image] Julia's type system : what am I missing? General Usage Adding to @Daniel_Berge 's answer, you can easily dispatch on more specific aliases: const Len{T} = Quantity{T,u"𝐋"} const Met{T} = Quantity{T,u"𝐋",typeof(m)} const Deg{T} = Quanti…

Dispatch on specific Unitful unit

General Usage

Nathan_Boyer July 11, 2025, 1:32pm 8

Saving this here for myself:

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Dispatch on specific Unitful unit

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