A .+ B .+ C differs from @. A+B+C

[mbauman]

The .+ syntax lowers to two binary calls whereas the macro uses the n-ary parsing from +:

julia> Meta.@lower A .+ B .+ C
:($(Expr(:thunk, CodeInfo(
 1 ─ %1 = (Base.getproperty)(Base.Broadcast, :materialize)              │
 │   %2 = (Base.getproperty)(Base.Broadcast, :broadcasted)              │
 │   %3 = (Base.getproperty)(Base.Broadcast, :broadcasted)              │
 │   %4 = (%3)(+, A, B)                                                 │
 │   %5 = (%2)(+, %4, C)                                                │
 │   %6 = (%1)(%5)                                                      │
 └──      return %6                                                     │
))))

julia> Meta.@lower @. A + B + C
:($(Expr(:thunk, CodeInfo(
 1 ─ %1 = (Base.getproperty)(Base.Broadcast, :materialize)              │
 │   %2 = (Base.getproperty)(Base.Broadcast, :broadcasted)              │
 │   %3 = (%2)(+, A, B, C)                                              │
 │   %4 = (%1)(%3)                                                      │
 └──      return %4                                                     │
))))

I actually like the parsing of A .+ B .+ C better as it makes life easier for us to keep .+ associative with respect to range behaviors — we only define the two-argument flavors. Perhaps we should split the n-ary calls to binary ones in @.? Unfortunately, the macro cannot distinguish between @. A + B + C and @. (+)(A, B, C).

[N5N3]

Maybe the broadcasteded call for these expandable funtion should be expanded at once, i.e.

for op in (:+, :*, :&, :|, :xor, :min, :max, :kron) 
    @eval begin
        @inline broadcasted(::typeof($op),x,y) = begin
            x′ = broadcastable(x)
            y′ = broadcastable(y)
            broadcasted(combine_styles(x′,y′), $op, x′, y′)
        end
        broadcasted(::typeof($op),x,y,args...) = begin
            temp = broadcasted($op,x,y)
            broadcasted($op,temp,args...)
        end
    end
end

I copy the symbol list from the Base, only :* and :+ is really needed