Broadcasting over structs in 1.0: what am I supposed to do?

General Usage
1

Hi all-

I commonly broadcast over structs with the dot syntax. While updating my code, I was dismayed to see this is longer a simple process. Here is a minimum working example just for reference:

mutable struct M
    x::Int 
end 
m = M(1)
f(m,x) = x/m.x
y = [1,2,3]
f.(m,y)

This code results in the following warning:

┌ Warning: broadcast will default to iterating over its arguments in the future. Wrap arguments of
│ type `x::M` with `Ref(x)` to ensure they broadcast as "scalar" elements.
│   caller = ip:0x0
└ @ Core :-1

I was further dismayed because the warning message is confusing. It seems to indicate (1) I will (maybe?) have to use Ref(X) all over my code and (2) something will (might?) change in the future. After digging around, I encountered a long discussion that left me even more confused about the situation and what to do. Do I wrap my arguments like so: f.(Ref(m),y)? Do I simply declare Broadcast.broadcastable(x::M) = Ref(x) for each struct? Both currently work, but will it change? (And for what it’s worth if an extra step is necessary for broadcasting structs would strongly prefer to type Broadcast.broadcastable(x::M) = Ref(x) once rather than Ref(x) all over my code). I’m hoping someone one can clarify the situation so I can know how to proceed

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2 
julia> Broadcast.broadcastable(m::M) = Ref(m)

julia> f.(m,y)
3-element Array{Float64,1}:
 1.0
 2.0
 3.0

See help on broadcastable and https://docs.julialang.org/en/latest/manual/interfaces/#man-interfaces-broadcasting-1 for further information.

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3

Thank you for clarifying. I was looking for this information in the Broadcasting and Vectorization section.

4

Thanks, but shouldn’t “being broadcasted by Ref” be a default behavior of an instance?

The fact is, only when I use broadcasting, I will remember to define this trivil interface to prevent error.
On the other hand, adding this natural behavior to every struct is too expensive for developer.

Is this discussion serious?!
https://github.com/JuliaLang/julia/pull/26435

I will comment back!

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